COMPMID-585: Port OpticalFlow to new validation

Change-Id: Ia36bd11ca27420d3059eea15df81b237900149ec
Reviewed-on: https://eu-gerrit-1.euhpc.arm.com/125175
Tested-by: Jenkins <bsgcomp@arm.com>
Reviewed-by: John Richardson <john.richardson@arm.com>
Reviewed-by: Anthony Barbier <anthony.barbier@arm.com>

13 files changed, 1213 insertions, 40 deletions

diff --git a/src/core/CL/cl_kernels/optical_flow_pyramid_lk.cl b/src/core/CL/cl_kernels/optical_flow_pyramid_lk.cl
index 20474f0095..8a126a019c 100644
--- a/src/core/CL/cl_kernels/optical_flow_pyramid_lk.cl
+++ b/src/core/CL/cl_kernels/optical_flow_pyramid_lk.cl
@@ -167,7 +167,11 @@ __kernel void finalize(
     Keypoint new_point;
     new_point.x               = round(new_point_internal.x);
     new_point.y               = round(new_point_internal.y);
+    new_point.strength        = 0.f;
+    new_point.scale           = 0.f;
+    new_point.orientation     = 0.f;
     new_point.tracking_status = new_point_internal.tracking_status;
+    new_point.error           = 0.f;
 
     // Store new point
     new_points[idx] = new_point;
@@ -352,8 +356,7 @@ void __kernel lktracker_stage0(
  * @param[in]      border_limits                           It stores the right border limit (width - window_dimension - 1, height - window_dimension - 1,)
  * @param[in]      eig_const                               1.0f / (float)(2.0f * window_dimension * window_dimension)
  * @param[in]      level0                                  It is set to 1 if level of pyramid = 0
- * @param[in]      term_iteration                          It is set to 1 if termination = VX_TERM_CRITERIA_ITERATIONS
- * @param[in]      term_epsilon                            It is set to 1 if termination = VX_TERM_CRITERIA_EPSILON
+ * @param[in]      term_epsilon                            It is set to 1 if termination = TERM_CRITERIA_EPSILON
  */
 void __kernel lktracker_stage1(
     IMAGE_DECLARATION(new_image),
@@ -368,7 +371,6 @@ void __kernel lktracker_stage1(
     const float3     border_limits,
     const float      eig_const,
     const int        level0,
-    const int        term_iteration,
     const int        term_epsilon)
 {
     int   idx       = get_global_id(0);
@@ -512,10 +514,7 @@ void __kernel lktracker_stage1(
         // Update previous delta
         prev_delta = delta;
 
-        if(term_iteration == 1)
-        {
-            j++;
-        }
+        j++;
     }
 
     new_points[idx].xy = out_new_point;
diff --git a/src/core/CL/kernels/CLLKTrackerKernel.cpp b/src/core/CL/kernels/CLLKTrackerKernel.cpp
index 12cdd0ec93..078d18e61c 100644
--- a/src/core/CL/kernels/CLLKTrackerKernel.cpp
+++ b/src/core/CL/kernels/CLLKTrackerKernel.cpp
@@ -1,5 +1,5 @@
 /*
- * Copyright (c) 2017 ARM Limited.
+ * Copyright (c) 2017-2018 ARM Limited.
  *
  * SPDX-License-Identifier: MIT
  *
@@ -249,8 +249,12 @@ void CLLKTrackerStage1Kernel::configure(const ICLTensor *new_input, ICLLKInterna
             static_cast<cl_float>(valid_region.start(0))
         }
     };
-    const int term_iteration = (termination == Termination::TERM_CRITERIA_ITERATIONS || termination == Termination::TERM_CRITERIA_BOTH) ? 1 : 0;
-    const int term_epsilon   = (termination == Termination::TERM_CRITERIA_EPSILON || termination == Termination::TERM_CRITERIA_BOTH) ? 1 : 0;
+
+    // Set maximum number of iterations used for convergence
+    const size_t max_iterations = 1000;
+    num_iterations              = (termination == Termination::TERM_CRITERIA_EPSILON) ? max_iterations : num_iterations;
+
+    const int term_epsilon = (termination == Termination::TERM_CRITERIA_EPSILON || termination == Termination::TERM_CRITERIA_BOTH) ? 1 : 0;
 
     // Create kernel
     _kernel = static_cast<cl::Kernel>(CLKernelLibrary::get().create_kernel("lktracker_stage1"));
@@ -268,7 +272,6 @@ void CLLKTrackerStage1Kernel::configure(const ICLTensor *new_input, ICLLKInterna
     _kernel.setArg<cl_float3>(idx++, border_limits);
     _kernel.setArg<cl_float>(idx++, eig_const);
     _kernel.setArg<cl_int>(idx++, level0);
-    _kernel.setArg<cl_int>(idx++, term_iteration);
     _kernel.setArg<cl_int>(idx++, term_epsilon);
 }
 
diff --git a/src/core/NEON/kernels/NELKTrackerKernel.cpp b/src/core/NEON/kernels/NELKTrackerKernel.cpp
index 004ecd07ef..83593e7f0d 100644
--- a/src/core/NEON/kernels/NELKTrackerKernel.cpp
+++ b/src/core/NEON/kernels/NELKTrackerKernel.cpp
@@ -1,5 +1,5 @@
 /*
- * Copyright (c) 2016, 2017 ARM Limited.
+ * Copyright (c) 2016-2018 ARM Limited.
  *
  * SPDX-License-Identifier: MIT
  *
@@ -356,13 +356,16 @@ void NELKTrackerKernel::configure(const ITensor *input_old, const ITensor *input
     _termination          = termination;
     _use_initial_estimate = use_initial_estimate;
     _epsilon              = epsilon;
-    _num_iterations       = num_iterations;
     _window_dimension     = window_dimension;
     _level                = level;
     _num_levels           = num_levels;
     _pyramid_scale        = pyramid_scale;
     _num_levels           = num_levels;
 
+    // Set maximum number of iterations used for convergence
+    const size_t max_iterations = 1000;
+    _num_iterations             = (termination == Termination::TERM_CRITERIA_EPSILON) ? max_iterations : num_iterations;
+
     Window window;
     window.set(Window::DimX, Window::Dimension(0, old_points->num_values()));
     window.set(Window::DimY, Window::Dimension(0, 1));
@@ -471,7 +474,7 @@ void NELKTrackerKernel::run(const Window &window, const ThreadInfo &info)
         float prev_delta_x = 0.0f;
         float prev_delta_y = 0.0f;
 
-        for(unsigned int j = 0; j < _num_iterations || _termination == Termination::TERM_CRITERIA_EPSILON; ++j)
+        for(unsigned int j = 0; j < _num_iterations; ++j)
         {
             if(is_invalid_keypoint(new_keypoint))
             {
diff --git a/tests/AssetsLibrary.cpp b/tests/AssetsLibrary.cpp
index 1cbd3b4e3d..ee876f91e3 100644
--- a/tests/AssetsLibrary.cpp
+++ b/tests/AssetsLibrary.cpp
@@ -120,15 +120,15 @@ void discard_comments_and_spaces(std::ifstream &fs)
     }
 }
 
-std::tuple<unsigned int, unsigned int, int> parse_ppm_header(std::ifstream &fs)
+std::tuple<unsigned int, unsigned int, int> parse_netpbm_format_header(std::ifstream &fs, char number)
 {
-    // Check the PPM magic number is valid
+    // check file type magic number is valid
     std::array<char, 2> magic_number{ { 0 } };
     fs >> magic_number[0] >> magic_number[1];
 
-    if(magic_number[0] != 'P' || magic_number[1] != '6')
+    if(magic_number[0] != 'P' || magic_number[1] != number)
     {
-        throw std::runtime_error("Only raw PPM format is suported");
+        throw std::runtime_error("File type magic number not supported");
     }
 
     discard_comments_and_spaces(fs);
@@ -160,7 +160,7 @@ std::tuple<unsigned int, unsigned int, int> parse_ppm_header(std::ifstream &fs)
 
     if(isspace(fs.peek()) == 0)
     {
-        throw std::runtime_error("Invalid PPM header");
+        throw std::runtime_error("Invalid image header");
     }
 
     fs.ignore(1);
@@ -168,6 +168,39 @@ std::tuple<unsigned int, unsigned int, int> parse_ppm_header(std::ifstream &fs)
     return std::make_tuple(width, height, max_value);
 }
 
+std::tuple<unsigned int, unsigned int, int> parse_ppm_header(std::ifstream &fs)
+{
+    return parse_netpbm_format_header(fs, '6');
+}
+
+std::tuple<unsigned int, unsigned int, int> parse_pgm_header(std::ifstream &fs)
+{
+    return parse_netpbm_format_header(fs, '5');
+}
+
+void check_image_size(std::ifstream &fs, size_t raw_size)
+{
+    const size_t current_position = fs.tellg();
+    fs.seekg(0, std::ios_base::end);
+    const size_t end_position = fs.tellg();
+    fs.seekg(current_position, std::ios_base::beg);
+
+    if((end_position - current_position) < raw_size)
+    {
+        throw std::runtime_error("Not enough data in file");
+    }
+}
+
+void read_image_buffer(std::ifstream &fs, RawTensor &raw)
+{
+    fs.read(reinterpret_cast<std::fstream::char_type *>(raw.data()), raw.size());
+
+    if(!fs.good())
+    {
+        throw std::runtime_error("Failure while reading image buffer");
+    }
+}
+
 RawTensor load_ppm(const std::string &path)
 {
     std::ifstream file(path, std::ios::in | std::ios::binary);
@@ -184,24 +217,31 @@ RawTensor load_ppm(const std::string &path)
 
     RawTensor raw(TensorShape(width, height), Format::RGB888);
 
-    // Check if the file is large enough to fill the image
-    const size_t current_position = file.tellg();
-    file.seekg(0, std::ios_base::end);
-    const size_t end_position = file.tellg();
-    file.seekg(current_position, std::ios_base::beg);
+    check_image_size(file, raw.size());
+    read_image_buffer(file, raw);
 
-    if((end_position - current_position) < raw.size())
-    {
-        throw std::runtime_error("Not enough data in file");
-    }
+    return raw;
+}
 
-    file.read(reinterpret_cast<std::fstream::char_type *>(raw.data()), raw.size());
+RawTensor load_pgm(const std::string &path)
+{
+    std::ifstream file(path, std::ios::in | std::ios::binary);
 
     if(!file.good())
     {
-        throw std::runtime_error("Failure while reading image buffer");
+        throw framework::FileNotFound("Could not load PGM image: " + path);
     }
 
+    unsigned int width  = 0;
+    unsigned int height = 0;
+
+    std::tie(width, height, std::ignore) = parse_pgm_header(file);
+
+    RawTensor raw(TensorShape(width, height), Format::U8);
+
+    check_image_size(file, raw.size());
+    read_image_buffer(file, raw);
+
     return raw;
 }
 } // namespace
@@ -244,7 +284,8 @@ const AssetsLibrary::Loader &AssetsLibrary::get_loader(const std::string &extens
 {
     static std::unordered_map<std::string, Loader> loaders =
     {
-        { "ppm", load_ppm }
+        { "ppm", load_ppm },
+        { "pgm", load_pgm }
     };
 
     const auto it = loaders.find(extension);
diff --git a/tests/Types.h b/tests/Types.h
index f6ceb13de4..c65b56c1ba 100644
--- a/tests/Types.h
+++ b/tests/Types.h
@@ -59,5 +59,37 @@ struct MinMaxLocationValues
     std::vector<Coordinates2D> min_loc{}; /**< Min value location */
     std::vector<Coordinates2D> max_loc{}; /**< Max value location */
 };
+
+/** Parameters of Optical Flow algorithm. */
+struct OpticalFlowParameters
+{
+    OpticalFlowParameters(Termination termination,
+                          float       epsilon,
+                          size_t      num_iterations,
+                          size_t      window_dimension,
+                          bool        use_initial_estimate)
+        : termination{ std::move(termination) },
+          epsilon{ std::move(epsilon) },
+          num_iterations{ std::move(num_iterations) },
+          window_dimension{ std::move(window_dimension) },
+          use_initial_estimate{ std::move(use_initial_estimate) }
+    {
+    }
+
+    Termination termination;
+    float       epsilon;
+    size_t      num_iterations;
+    size_t      window_dimension;
+    bool        use_initial_estimate;
+};
+
+/** Internal keypoint class for Lucas-Kanade Optical Flow */
+struct InternalKeyPoint
+{
+    float x{ 0.f };                 /**< x coordinate of the keypoint */
+    float y{ 0.f };                 /**< y coordinate of the keypoint */
+    bool  tracking_status{ false }; /**< the tracking status of the keypoint */
+};
+
 } // namespace arm_compute
 #endif /* __ARM_COMPUTE_TEST_TYPES_H__ */
diff --git a/tests/Utils.h b/tests/Utils.h
index 4feed4e491..7d960dd08f 100644
--- a/tests/Utils.h
+++ b/tests/Utils.h
@@ -28,6 +28,7 @@
 #include "arm_compute/core/Error.h"
 #include "arm_compute/core/FixedPoint.h"
 #include "arm_compute/core/HOGInfo.h"
+#include "arm_compute/core/PyramidInfo.h"
 #include "arm_compute/core/Size2D.h"
 #include "arm_compute/core/TensorInfo.h"
 #include "arm_compute/core/TensorShape.h"
@@ -548,6 +549,21 @@ inline T create_HOG(const HOGInfo &hog_info)
     return hog;
 }
 
+/** Create and initialize a Pyramid of the given type.
+ *
+ * @param[in] pyramid_info The PyramidInfo object.
+ *
+ * @return Initialized Pyramid of given type.
+ */
+template <typename T>
+inline T create_pyramid(const PyramidInfo &pyramid_info)
+{
+    T pyramid;
+    pyramid.init_auto_padding(pyramid_info);
+
+    return pyramid;
+}
+
 /** Create a vector of random ROIs.
  *
  * @param[in] shape     The shape of the input tensor.
@@ -618,6 +634,44 @@ inline std::vector<T> generate_random_real(unsigned int num_values, T min, T max
     return v;
 }
 
+/** Create a vector of random keypoints for pyramid representation.
+ *
+ * @param[in] shape         The shape of the input tensor.
+ * @param[in] num_keypoints The number of keypoints to be created.
+ * @param[in] seed          The random seed to be used.
+ * @param[in] num_levels    The number of pyramid levels.
+ *
+ * @return A vector that contains the requested number of random keypoints
+ */
+inline std::vector<KeyPoint> generate_random_keypoints(const TensorShape &shape, size_t num_keypoints, std::random_device::result_type seed, size_t num_levels = 1)
+{
+    std::vector<KeyPoint> keypoints;
+    std::mt19937          gen(seed);
+
+    // Calculate distribution bounds
+    const auto min        = static_cast<int>(std::pow(2, num_levels));
+    const auto max_width  = static_cast<int>(shape.x());
+    const auto max_height = static_cast<int>(shape.y());
+
+    ARM_COMPUTE_ERROR_ON(min > max_width || min > max_height);
+
+    // Create distributions
+    std::uniform_int_distribution<> dist_w(min, max_width);
+    std::uniform_int_distribution<> dist_h(min, max_height);
+
+    for(unsigned int i = 0; i < num_keypoints; i++)
+    {
+        KeyPoint keypoint;
+        keypoint.x               = dist_w(gen);
+        keypoint.y               = dist_h(gen);
+        keypoint.tracking_status = 1;
+
+        keypoints.push_back(keypoint);
+    }
+
+    return keypoints;
+}
+
 template <typename T, typename ArrayAccessor_T>
 inline void fill_array(ArrayAccessor_T &&array, const std::vector<T> &v)
 {
diff --git a/tests/datasets/OpticalFlowDataset.h b/tests/datasets/OpticalFlowDataset.h
new file mode 100644
index 0000000000..9e247206f8
--- /dev/null
+++ b/tests/datasets/OpticalFlowDataset.h
@@ -0,0 +1,165 @@
+/*
+ * Copyright (c) 2018 ARM Limited.
+ *
+ * SPDX-License-Identifier: MIT
+ *
+ * Permission is hereby granted, free of charge, to any person obtaining a copy
+ * of this software and associated documentation files (the "Software"), to
+ * deal in the Software without restriction, including without limitation the
+ * rights to use, copy, modify, merge, publish, distribute, sublicense, and/or
+ * sell copies of the Software, and to permit persons to whom the Software is
+ * furnished to do so, subject to the following conditions:
+ *
+ * The above copyright notice and this permission notice shall be included in all
+ * copies or substantial portions of the Software.
+ *
+ * THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
+ * IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
+ * FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE
+ * AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
+ * LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM,
+ * OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN THE
+ * SOFTWARE.
+ */
+#ifndef ARM_COMPUTE_TEST_OPTICAL_FLOW_DATASET
+#define ARM_COMPUTE_TEST_OPTICAL_FLOW_DATASET
+
+#include "tests/validation/Helpers.h"
+#include "utils/TypePrinter.h"
+
+namespace arm_compute
+{
+namespace test
+{
+namespace datasets
+{
+class OpticalFlowDataset
+{
+public:
+    using type = std::tuple<std::string, std::string, OpticalFlowParameters, size_t, size_t>;
+
+    struct iterator
+    {
+        iterator(std::vector<std::string>::const_iterator           old_image_it,
+                 std::vector<std::string>::const_iterator           new_image_it,
+                 std::vector<OpticalFlowParameters>::const_iterator params_it,
+                 std::vector<size_t>::const_iterator                num_levels_it,
+                 std::vector<size_t>::const_iterator                num_keypoints_it)
+            : _old_image_it{ std::move(old_image_it) },
+              _new_image_it{ std::move(new_image_it) },
+              _params_it{ std::move(params_it) },
+              _num_levels_it{ std::move(num_levels_it) },
+              _num_keypoints_it{ std::move(num_keypoints_it) }
+        {
+        }
+
+        std::string description() const
+        {
+            std::stringstream description;
+            description << "NumLevels=" << *_num_levels_it << ":";
+            description << "NumKeypoints=" << *_num_keypoints_it << ":";
+            description << "Termination=" << _params_it->termination << ":";
+            description << "Epsilon=" << _params_it->epsilon << ":";
+            description << "NumIterations=" << _params_it->num_iterations << ":";
+            description << "WindowDimension=" << _params_it->window_dimension << ":";
+            description << "InitialEstimate=" << std::boolalpha << _params_it->use_initial_estimate;
+
+            return description.str();
+        }
+
+        OpticalFlowDataset::type operator*() const
+        {
+            return std::make_tuple(*_old_image_it, *_new_image_it, *_params_it, *_num_levels_it, *_num_keypoints_it);
+        }
+
+        iterator &operator++()
+        {
+            ++_old_image_it;
+            ++_new_image_it;
+            ++_params_it;
+            ++_num_levels_it;
+            ++_num_keypoints_it;
+
+            return *this;
+        }
+
+    private:
+        std::vector<std::string>::const_iterator           _old_image_it;
+        std::vector<std::string>::const_iterator           _new_image_it;
+        std::vector<OpticalFlowParameters>::const_iterator _params_it;
+        std::vector<size_t>::const_iterator                _num_levels_it;
+        std::vector<size_t>::const_iterator                _num_keypoints_it;
+    };
+
+    iterator begin() const
+    {
+        return iterator(_old_image.begin(),
+                        _new_image.begin(),
+                        _params.begin(),
+                        _num_levels.begin(),
+                        _num_keypoints.begin());
+    }
+
+    int size() const
+    {
+        return std::min(_old_image.size(), std::min(_new_image.size(), std::min(_params.size(), std::min(_num_levels.size(), _num_keypoints.size()))));
+    }
+
+    void add_config(std::string old_image, std::string new_image, OpticalFlowParameters params, size_t num_levels, size_t num_keypoints)
+    {
+        _old_image.emplace_back(std::move(old_image));
+        _new_image.emplace_back(std::move(new_image));
+        _params.emplace_back(params);
+        _num_levels.emplace_back(num_levels);
+        _num_keypoints.emplace_back(num_keypoints);
+    }
+
+protected:
+    OpticalFlowDataset()                      = default;
+    OpticalFlowDataset(OpticalFlowDataset &&) = default;
+
+private:
+    std::vector<std::string>           _old_image{};
+    std::vector<std::string>           _new_image{};
+    std::vector<OpticalFlowParameters> _params{};
+    std::vector<size_t>                _num_levels{};
+    std::vector<size_t>                _num_keypoints{};
+};
+
+// *INDENT-OFF*
+// clang-format off
+class SmallOpticalFlowDataset final : public OpticalFlowDataset
+{
+public:
+    SmallOpticalFlowDataset()
+    {
+        //         old_image              new_image              (termination, epsilon, num_iterations, window_dimension, initial_estimate) levels keypoints
+        add_config("opticalflow_old.pgm", "opticalflow_new.pgm", OpticalFlowParameters(Termination::TERM_CRITERIA_BOTH,       0.01f, 3, 5, true), 3, 1000);
+        add_config("opticalflow_old.pgm", "opticalflow_new.pgm", OpticalFlowParameters(Termination::TERM_CRITERIA_EPSILON,    0.01f, 3, 5, true), 3, 1000);
+        add_config("opticalflow_old.pgm", "opticalflow_new.pgm", OpticalFlowParameters(Termination::TERM_CRITERIA_ITERATIONS, 0.01f, 3, 5, true), 3, 1000);
+    }
+};
+
+class LargeOpticalFlowDataset final : public OpticalFlowDataset
+{
+public:
+    LargeOpticalFlowDataset()
+    {
+        //         old_image              new_image              (termination, epsilon, num_iterations, window_dimension, initial_estimate) levels keypoints
+        add_config("opticalflow_old.pgm", "opticalflow_new.pgm", OpticalFlowParameters(Termination::TERM_CRITERIA_BOTH,       0.01f, 3, 5, true), 3, 10000);
+        add_config("opticalflow_old.pgm", "opticalflow_new.pgm", OpticalFlowParameters(Termination::TERM_CRITERIA_EPSILON,    0.01f, 3, 5, true), 3, 10000);
+        add_config("opticalflow_old.pgm", "opticalflow_new.pgm", OpticalFlowParameters(Termination::TERM_CRITERIA_ITERATIONS, 0.01f, 3, 5, true), 3, 10000);
+
+        //         old_image              new_image              (termination, epsilon, num_iterations, window_dimension, initial_estimate) levels keypoints
+        add_config("opticalflow_old.pgm", "opticalflow_new.pgm", OpticalFlowParameters(Termination::TERM_CRITERIA_BOTH,       0.01f, 3, 5, false), 3, 10000);
+        add_config("opticalflow_old.pgm", "opticalflow_new.pgm", OpticalFlowParameters(Termination::TERM_CRITERIA_EPSILON,    0.01f, 3, 5, false), 3, 10000);
+        add_config("opticalflow_old.pgm", "opticalflow_new.pgm", OpticalFlowParameters(Termination::TERM_CRITERIA_ITERATIONS, 0.01f, 3, 5, false), 3, 10000);
+    }
+};
+// clang-format on
+// *INDENT-ON*
+
+} // namespace datasets
+} // namespace test
+} // namespace arm_compute
+#endif /* ARM_COMPUTE_TEST_OPTICAL_FLOW_DATASET */
diff --git a/tests/validation/CL/OpticalFlow.cpp b/tests/validation/CL/OpticalFlow.cpp
new file mode 100644
index 0000000000..006d40a0e5
--- /dev/null
+++ b/tests/validation/CL/OpticalFlow.cpp
@@ -0,0 +1,93 @@
+/*
+ * Copyright (c) 2018 ARM Limited.
+ *
+ * SPDX-License-Identifier: MIT
+ *
+ * Permission is hereby granted, free of charge, to any person obtaining a copy
+ * of this software and associated documentation files (the "Software"), to
+ * deal in the Software without restriction, including without limitation the
+ * rights to use, copy, modify, merge, publish, distribute, sublicense, and/or
+ * sell copies of the Software, and to permit persons to whom the Software is
+ * furnished to do so, subject to the following conditions:
+ *
+ * The above copyright notice and this permission notice shall be included in all
+ * copies or substantial portions of the Software.
+ *
+ * THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
+ * IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
+ * FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE
+ * AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
+ * LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM,
+ * OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN THE
+ * SOFTWARE.
+ */
+#include "arm_compute/runtime/CL/CLArray.h"
+#include "arm_compute/runtime/CL/CLPyramid.h"
+#include "arm_compute/runtime/CL/functions/CLGaussianPyramid.h"
+#include "arm_compute/runtime/CL/functions/CLOpticalFlow.h"
+#include "arm_compute/runtime/Tensor.h"
+#include "tests/CL/CLAccessor.h"
+#include "tests/CL/CLArrayAccessor.h"
+#include "tests/datasets/BorderModeDataset.h"
+#include "tests/datasets/OpticalFlowDataset.h"
+#include "tests/framework/Asserts.h"
+#include "tests/framework/Macros.h"
+#include "tests/framework/datasets/Datasets.h"
+#include "tests/validation/Validation.h"
+#include "tests/validation/fixtures/OpticalFlowFixture.h"
+
+namespace arm_compute
+{
+namespace test
+{
+namespace validation
+{
+TEST_SUITE(CL)
+TEST_SUITE(OpticalFlow)
+
+// *INDENT-OFF*
+// clang-format off
+using CLOpticalFlowFixture = OpticalFlowValidationFixture<CLTensor,
+                                                          CLAccessor,
+                                                          CLKeyPointArray,
+                                                          CLArrayAccessor<KeyPoint>,
+                                                          CLOpticalFlow,
+                                                          CLPyramid,
+                                                          CLGaussianPyramidHalf,
+                                                          uint8_t>;
+
+FIXTURE_DATA_TEST_CASE(RunSmall, CLOpticalFlowFixture, framework::DatasetMode::PRECOMMIT, combine(combine(
+                       datasets::SmallOpticalFlowDataset(),
+                       framework::dataset::make("Format", Format::U8)),
+                       datasets::BorderModes()))
+{
+    // Validate output
+    CLArrayAccessor<KeyPoint> array(_target);
+
+    validate_keypoints(array.buffer(),
+                       array.buffer() + array.num_values(),
+                       _reference.begin(),
+                       _reference.end());
+}
+
+FIXTURE_DATA_TEST_CASE(RunLarge, CLOpticalFlowFixture, framework::DatasetMode::NIGHTLY, combine(combine(
+                       datasets::LargeOpticalFlowDataset(),
+                       framework::dataset::make("Format", Format::U8)),
+                       datasets::BorderModes()))
+{
+    // Validate output
+    CLArrayAccessor<KeyPoint> array(_target);
+
+    validate_keypoints(array.buffer(),
+                       array.buffer() + array.num_values(),
+                       _reference.begin(),
+                       _reference.end());
+}
+// clang-format on
+// *INDENT-ON*
+
+TEST_SUITE_END()
+TEST_SUITE_END()
+} // namespace validation
+} // namespace test
+} // namespace arm_compute
diff --git a/tests/validation/NEON/OpticalFlow.cpp b/tests/validation/NEON/OpticalFlow.cpp
new file mode 100644
index 0000000000..1f4bf5fddf
--- /dev/null
+++ b/tests/validation/NEON/OpticalFlow.cpp
@@ -0,0 +1,92 @@
+/*
+ * Copyright (c) 2018 ARM Limited.
+ *
+ * SPDX-License-Identifier: MIT
+ *
+ * Permission is hereby granted, free of charge, to any person obtaining a copy
+ * of this software and associated documentation files (the "Software"), to
+ * deal in the Software without restriction, including without limitation the
+ * rights to use, copy, modify, merge, publish, distribute, sublicense, and/or
+ * sell copies of the Software, and to permit persons to whom the Software is
+ * furnished to do so, subject to the following conditions:
+ *
+ * The above copyright notice and this permission notice shall be included in all
+ * copies or substantial portions of the Software.
+ *
+ * THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
+ * IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
+ * FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE
+ * AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
+ * LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM,
+ * OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN THE
+ * SOFTWARE.
+ */
+#include "arm_compute/runtime/Array.h"
+#include "arm_compute/runtime/NEON/functions/NEGaussianPyramid.h"
+#include "arm_compute/runtime/NEON/functions/NEOpticalFlow.h"
+#include "arm_compute/runtime/Pyramid.h"
+#include "arm_compute/runtime/Tensor.h"
+#include "tests/NEON/Accessor.h"
+#include "tests/NEON/ArrayAccessor.h"
+#include "tests/datasets/BorderModeDataset.h"
+#include "tests/datasets/OpticalFlowDataset.h"
+#include "tests/framework/Asserts.h"
+#include "tests/framework/Macros.h"
+#include "tests/framework/datasets/Datasets.h"
+#include "tests/validation/Validation.h"
+#include "tests/validation/fixtures/OpticalFlowFixture.h"
+
+namespace arm_compute
+{
+namespace test
+{
+namespace validation
+{
+TEST_SUITE(NEON)
+TEST_SUITE(OpticalFlow)
+
+// *INDENT-OFF*
+// clang-format off
+using NEOpticalFlowFixture = OpticalFlowValidationFixture<Tensor,
+                                                          Accessor,
+                                                          KeyPointArray,
+                                                          ArrayAccessor<KeyPoint>,
+                                                          NEOpticalFlow,
+                                                          Pyramid,
+                                                          NEGaussianPyramidHalf,
+                                                          uint8_t>;
+
+FIXTURE_DATA_TEST_CASE(RunSmall, NEOpticalFlowFixture, framework::DatasetMode::PRECOMMIT, combine(combine(
+                       datasets::SmallOpticalFlowDataset(),
+                       framework::dataset::make("Format", Format::U8)),
+                       datasets::BorderModes()))
+{
+    // Validate output
+    ArrayAccessor<KeyPoint> array(_target);
+    validate_keypoints(array.buffer(),
+                       array.buffer() + array.num_values(),
+                       _reference.begin(),
+                       _reference.end());
+}
+
+FIXTURE_DATA_TEST_CASE(RunLarge, NEOpticalFlowFixture, framework::DatasetMode::NIGHTLY, combine(combine(
+                       datasets::LargeOpticalFlowDataset(),
+                       framework::dataset::make("Format", Format::U8)),
+                       datasets::BorderModes()))
+{
+    // Validate output
+    ArrayAccessor<KeyPoint> array(_target);
+
+    validate_keypoints(array.buffer(),
+                       array.buffer() + array.num_values(),
+                       _reference.begin(),
+                       _reference.end());
+}
+// clang-format on
+// *INDENT-ON*
+
+TEST_SUITE_END()
+TEST_SUITE_END()
+} // namespace validation
+} // namespace test
+} // namespace arm_compute
diff --git a/tests/validation/fixtures/OpticalFlowFixture.h b/tests/validation/fixtures/OpticalFlowFixture.h
new file mode 100644
index 0000000000..f8f2021533
--- /dev/null
+++ b/tests/validation/fixtures/OpticalFlowFixture.h
@@ -0,0 +1,186 @@
+/*
+ * Copyright (c) 2018 ARM Limited.
+ *
+ * SPDX-License-Identifier: MIT
+ *
+ * Permission is hereby granted, free of charge, to any person obtaining a copy
+ * of this software and associated documentation files (the "Software"), to
+ * deal in the Software without restriction, including without limitation the
+ * rights to use, copy, modify, merge, publish, distribute, sublicense, and/or
+ * sell copies of the Software, and to permit persons to whom the Software is
+ * furnished to do so, subject to the following conditions:
+ *
+ * The above copyright notice and this permission notice shall be included in all
+ * copies or substantial portions of the Software.
+ *
+ * THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
+ * IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
+ * FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE
+ * AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
+ * LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM,
+ * OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN THE
+ * SOFTWARE.
+ */
+#ifndef ARM_COMPUTE_TEST_OPTICAL_FLOW
+#define ARM_COMPUTE_TEST_OPTICAL_FLOW
+
+#include "arm_compute/core/PyramidInfo.h"
+#include "arm_compute/core/TensorShape.h"
+#include "arm_compute/core/Types.h"
+#include "tests/AssetsLibrary.h"
+#include "tests/Globals.h"
+#include "tests/IAccessor.h"
+#include "tests/Types.h"
+#include "tests/framework/Asserts.h"
+#include "tests/framework/Fixture.h"
+#include "tests/validation/reference/OpticalFlow.h"
+
+namespace arm_compute
+{
+namespace test
+{
+namespace validation
+{
+template <typename TensorType,
+          typename AccessorType,
+          typename ArrayType,
+          typename ArrayAccessorType,
+          typename FunctionType,
+          typename PyramidType,
+          typename PyramidFunctionType,
+          typename T>
+
+class OpticalFlowValidationFixture : public framework::Fixture
+{
+public:
+    template <typename...>
+    void setup(std::string old_image_name, std::string new_image_name, OpticalFlowParameters params,
+               size_t num_levels, size_t num_keypoints, Format format, BorderMode border_mode)
+    {
+        std::mt19937                           gen(library->seed());
+        std::uniform_int_distribution<uint8_t> int_dist(0, 255);
+        const uint8_t                          constant_border_value = int_dist(gen);
+
+        // Create keypoints
+        std::vector<KeyPoint> old_keypoints           = generate_random_keypoints(library->get_image_shape(old_image_name), num_keypoints, library->seed(), num_levels);
+        std::vector<KeyPoint> new_keypoints_estimates = old_keypoints;
+
+        _target    = compute_target(old_image_name, new_image_name, params, num_levels, old_keypoints, new_keypoints_estimates, format, border_mode, constant_border_value);
+        _reference = compute_reference(old_image_name, new_image_name, params, num_levels, old_keypoints, new_keypoints_estimates, format, border_mode, constant_border_value);
+    }
+
+protected:
+    template <typename V>
+    void fill(V &&tensor, const std::string image, Format format)
+    {
+        library->fill(tensor, image, format);
+    }
+
+    ArrayType compute_target(std::string old_image_name, std::string new_image_name, OpticalFlowParameters params, size_t num_levels,
+                             std::vector<KeyPoint> &old_keypoints, std::vector<KeyPoint> &new_keypoints_estimates,
+                             Format format, BorderMode border_mode, uint8_t constant_border_value)
+    {
+        // Get image shapes
+        TensorShape old_shape = library->get_image_shape(old_image_name);
+        TensorShape new_shape = library->get_image_shape(new_image_name);
+
+        // Create tensors
+        auto old_image = create_tensor<TensorType>(old_shape, format);
+        auto new_image = create_tensor<TensorType>(new_shape, format);
+
+        // Load keypoints
+        ArrayType old_points(old_keypoints.size());
+        ArrayType new_points_estimates(new_keypoints_estimates.size());
+        ArrayType new_points(old_keypoints.size());
+
+        fill_array(ArrayAccessorType(old_points), old_keypoints);
+        fill_array(ArrayAccessorType(new_points_estimates), new_keypoints_estimates);
+
+        // Create pyramid images
+        PyramidInfo pyramid_info(num_levels, SCALE_PYRAMID_HALF, old_image.info()->tensor_shape(), format);
+        PyramidType old_pyramid = create_pyramid<PyramidType>(pyramid_info);
+        PyramidType new_pyramid = create_pyramid<PyramidType>(pyramid_info);
+
+        // Create and configure pyramid functions
+        PyramidFunctionType old_gp;
+        old_gp.configure(&old_image, &old_pyramid, border_mode, constant_border_value);
+
+        PyramidFunctionType new_gp;
+        new_gp.configure(&new_image, &new_pyramid, border_mode, constant_border_value);
+
+        for(size_t i = 0; i < pyramid_info.num_levels(); ++i)
+        {
+            ARM_COMPUTE_EXPECT(old_pyramid.get_pyramid_level(i)->info()->is_resizable(), framework::LogLevel::ERRORS);
+            ARM_COMPUTE_EXPECT(new_pyramid.get_pyramid_level(i)->info()->is_resizable(), framework::LogLevel::ERRORS);
+        }
+
+        // Create and configure optical flow function
+        FunctionType optical_flow;
+
+        optical_flow.configure(&old_pyramid,
+                               &new_pyramid,
+                               &old_points,
+                               &new_points_estimates,
+                               &new_points,
+                               params.termination,
+                               params.epsilon,
+                               params.num_iterations,
+                               params.window_dimension,
+                               params.use_initial_estimate,
+                               border_mode,
+                               constant_border_value);
+
+        ARM_COMPUTE_EXPECT(old_image.info()->is_resizable(), framework::LogLevel::ERRORS);
+        ARM_COMPUTE_EXPECT(new_image.info()->is_resizable(), framework::LogLevel::ERRORS);
+
+        // Allocate input tensors
+        old_image.allocator()->allocate();
+        new_image.allocator()->allocate();
+
+        // Allocate pyramids
+        old_pyramid.allocate();
+        new_pyramid.allocate();
+
+        ARM_COMPUTE_EXPECT(!old_image.info()->is_resizable(), framework::LogLevel::ERRORS);
+        ARM_COMPUTE_EXPECT(!new_image.info()->is_resizable(), framework::LogLevel::ERRORS);
+
+        for(size_t i = 0; i < pyramid_info.num_levels(); ++i)
+        {
+            ARM_COMPUTE_EXPECT(!old_pyramid.get_pyramid_level(i)->info()->is_resizable(), framework::LogLevel::ERRORS);
+            ARM_COMPUTE_EXPECT(!new_pyramid.get_pyramid_level(i)->info()->is_resizable(), framework::LogLevel::ERRORS);
+        }
+
+        // Fill tensors
+        fill(AccessorType(old_image), old_image_name, format);
+        fill(AccessorType(new_image), new_image_name, format);
+
+        // Compute functions
+        old_gp.run();
+        new_gp.run();
+        optical_flow.run();
+
+        return new_points;
+    }
+
+    std::vector<KeyPoint> compute_reference(std::string old_image_name, std::string new_image_name,
+                                            OpticalFlowParameters params, size_t num_levels,
+                                            std::vector<KeyPoint> &old_keypoints, std::vector<KeyPoint> &new_keypoints_estimates,
+                                            Format format, BorderMode border_mode, uint8_t constant_border_value)
+    {
+        SimpleTensor<T> old_image{ library->get_image_shape(old_image_name), data_type_from_format(format) };
+        SimpleTensor<T> new_image{ library->get_image_shape(new_image_name), data_type_from_format(format) };
+
+        fill(old_image, old_image_name, format);
+        fill(new_image, new_image_name, format);
+
+        return reference::optical_flow<T>(old_image, new_image, params, num_levels, old_keypoints, new_keypoints_estimates,
+                                          border_mode, constant_border_value);
+    }
+
+    ArrayType             _target{};
+    std::vector<KeyPoint> _reference{};
+};
+} // namespace validation
+} // namespace test
+} // namespace arm_compute
+#endif /* ARM_COMPUTE_TEST_OPTICAL_FLOW */
diff --git a/tests/validation/reference/OpticalFlow.cpp b/tests/validation/reference/OpticalFlow.cpp
new file mode 100644
index 0000000000..da0b9f9f94
--- /dev/null
+++ b/tests/validation/reference/OpticalFlow.cpp
@@ -0,0 +1,404 @@
+/*
+ * Copyright (c) 2018 ARM Limited.
+ *
+ * SPDX-License-Identifier: MIT
+ *
+ * Permission is hereby granted, free of charge, to any person obtaining a copy
+ * of this software and associated documentation files (the "Software"), to
+ * deal in the Software without restriction, including without limitation the
+ * rights to use, copy, modify, merge, publish, distribute, sublicense, and/or
+ * sell copies of the Software, and to permit persons to whom the Software is
+ * furnished to do so, subject to the following conditions:
+ *
+ * The above copyright notice and this permission notice shall be included in all
+ * copies or substantial portions of the Software.
+ *
+ * THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
+ * IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
+ * FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE
+ * AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
+ * LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM,
+ * OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN THE
+ * SOFTWARE.
+ */
+#include "OpticalFlow.h"
+
+#include "GaussianPyramidHalf.h"
+#include "Scharr.h"
+#include "Utils.h"
+
+namespace arm_compute
+{
+namespace test
+{
+namespace validation
+{
+namespace reference
+{
+namespace
+{
+using KeyPointArray         = std::vector<KeyPoint>;
+using InternalKeyPointArray = std::vector<InternalKeyPoint>;
+
+// Constants used for Lucas-Kanade Algorithm
+constexpr int   W_BITS                = 14;
+constexpr float D0                    = 1 << W_BITS;
+constexpr float DETERMINANT_THRESHOLD = 1.0e-07f;
+constexpr float EIGENVALUE_THRESHOLD  = 1.0e-04f;
+constexpr float FLT_SCALE             = 1.0f / (1 << 20);
+
+// Creates an InternalKeyPointArray for tracking non-integral pixel coordinates
+InternalKeyPointArray create_internal_keypoints(const KeyPointArray &keypoints)
+{
+    InternalKeyPointArray internal_keypoints;
+
+    for(auto keypoint : keypoints)
+    {
+        InternalKeyPoint internal_keypoint;
+
+        internal_keypoint.x               = static_cast<float>(keypoint.x);
+        internal_keypoint.y               = static_cast<float>(keypoint.y);
+        internal_keypoint.tracking_status = static_cast<bool>(keypoint.tracking_status);
+
+        internal_keypoints.push_back(internal_keypoint);
+    }
+
+    return internal_keypoints;
+}
+
+// Scale tracked points based on Pyramid level
+void scale_tracked_points(size_t level, size_t num_levels, bool use_initial_estimate,
+                          InternalKeyPointArray &old_points_internal, InternalKeyPointArray &new_points_internal,
+                          const KeyPointArray &old_points, const KeyPointArray &new_points_estimates)
+{
+    if(level == num_levels - 1) // lowest resolution
+    {
+        const float scale = std::pow(SCALE_PYRAMID_HALF, level);
+
+        for(size_t i = 0; i < old_points.size(); ++i)
+        {
+            old_points_internal.at(i).x               = old_points.at(i).x * scale;
+            old_points_internal.at(i).y               = old_points.at(i).y * scale;
+            old_points_internal.at(i).tracking_status = true;
+
+            InternalKeyPoint keypoint_to_track;
+
+            if(use_initial_estimate)
+            {
+                keypoint_to_track.x               = new_points_estimates.at(i).x * scale;
+                keypoint_to_track.y               = new_points_estimates.at(i).y * scale;
+                keypoint_to_track.tracking_status = (new_points_estimates.at(i).tracking_status == 1);
+            }
+            else
+            {
+                keypoint_to_track.x               = old_points_internal.at(i).x;
+                keypoint_to_track.y               = old_points_internal.at(i).y;
+                keypoint_to_track.tracking_status = true;
+            }
+
+            new_points_internal.at(i) = keypoint_to_track;
+        }
+    }
+    else
+    {
+        for(size_t i = 0; i < old_points.size(); ++i)
+        {
+            old_points_internal.at(i).x /= SCALE_PYRAMID_HALF;
+            old_points_internal.at(i).y /= SCALE_PYRAMID_HALF;
+            new_points_internal.at(i).x /= SCALE_PYRAMID_HALF;
+            new_points_internal.at(i).y /= SCALE_PYRAMID_HALF;
+        }
+    }
+}
+
+bool is_invalid_keypoint(const InternalKeyPoint &keypoint, const ValidRegion &valid_region, size_t window_dimension)
+{
+    const int half_window = window_dimension / 2;
+    const int x           = std::floor(keypoint.x);
+    const int y           = std::floor(keypoint.y);
+
+    return (x - half_window < valid_region.start(0)) || (x + half_window >= valid_region.end(0) - 1) || (y - half_window < valid_region.start(1)) || (y + half_window >= valid_region.end(1) - 1);
+}
+
+template <typename T>
+constexpr int INT_ROUND(T x, int n)
+{
+    return (x + (1 << (n - 1))) >> n;
+}
+
+// Return the bilinear value at a specified coordinate with different border modes
+template <typename T>
+int bilinear_interpolate(const SimpleTensor<T> &in, Coordinates id, float wx, float wy, BorderMode border_mode, T constant_border_value, int scale)
+{
+    const int level = id.x();
+    const int idy   = id.y();
+
+    const float dx   = wx;
+    const float dy   = wy;
+    const float dx_1 = 1.0f - dx;
+    const float dy_1 = 1.0f - dy;
+
+    const T border_value = constant_border_value;
+
+    id.set(0, level);
+    id.set(1, idy);
+    const T tl = tensor_elem_at(in, id, border_mode, border_value);
+    id.set(0, level + 1);
+    id.set(1, idy);
+    const T tr = tensor_elem_at(in, id, border_mode, border_value);
+    id.set(0, level);
+    id.set(1, idy + 1);
+    const T bl = tensor_elem_at(in, id, border_mode, border_value);
+    id.set(0, level + 1);
+    id.set(1, idy + 1);
+    const T br = tensor_elem_at(in, id, border_mode, border_value);
+
+    // weights
+    const int w00 = roundf(dx_1 * dy_1 * D0);
+    const int w01 = roundf(dx * dy_1 * D0);
+    const int w10 = roundf(dx_1 * dy * D0);
+    const int w11 = D0 - w00 - w01 - w10;
+
+    return static_cast<int>(INT_ROUND(tl * w00 + tr * w01 + bl * w10 + br * w11, scale));
+}
+
+template <typename T>
+std::vector<int> compute_derivative(const SimpleTensor<T> &input, const InternalKeyPoint &keypoint,
+                                    BorderMode border_mode, uint8_t constant_border_value, size_t window_dimension, int scale)
+{
+    std::vector<int> bilinear_values;
+
+    const int half_window = window_dimension / 2;
+
+    float keypoint_int_x = 0;
+    float keypoint_int_y = 0;
+
+    const float wx = std::modf(keypoint.x, &keypoint_int_x);
+    const float wy = std::modf(keypoint.y, &keypoint_int_y);
+
+    Coordinates tl_window(static_cast<int>(keypoint_int_x) - half_window, static_cast<int>(keypoint_int_y) - half_window);
+    Coordinates br_window(static_cast<int>(keypoint_int_x) + half_window, static_cast<int>(keypoint_int_y) + half_window);
+
+    for(int y = tl_window.y(); y <= br_window.y(); ++y)
+    {
+        for(int x = tl_window.x(); x <= br_window.x(); ++x)
+        {
+            bilinear_values.push_back(bilinear_interpolate(input, Coordinates(x, y), wx, wy, border_mode, static_cast<T>(constant_border_value), scale));
+        }
+    }
+
+    return bilinear_values;
+}
+
+std::tuple<float, float, float> compute_spatial_gradient_matrix(const std::vector<int> &bilinear_ix, const std::vector<int> &bilinear_iy)
+{
+    ARM_COMPUTE_ERROR_ON(bilinear_ix.size() != bilinear_iy.size());
+
+    int iA11 = 0;
+    int iA12 = 0;
+    int iA22 = 0;
+
+    for(size_t i = 0; i < bilinear_ix.size(); ++i)
+    {
+        int ixval = bilinear_ix[i];
+        int iyval = bilinear_iy[i];
+
+        iA11 += ixval * ixval;
+        iA12 += ixval * iyval;
+        iA22 += iyval * iyval;
+    }
+
+    return std::make_tuple(iA11 * FLT_SCALE, iA12 * FLT_SCALE, iA22 * FLT_SCALE);
+}
+
+std::tuple<double, double> compute_temporal_gradient_vector(const std::vector<int> &bilinear_it_old,
+                                                            const std::vector<int> &bilinear_it_new,
+                                                            const std::vector<int> &bilinear_ix,
+                                                            const std::vector<int> &bilinear_iy)
+{
+    ARM_COMPUTE_ERROR_ON(bilinear_ix.size() != bilinear_iy.size());
+    ARM_COMPUTE_ERROR_ON(bilinear_it_old.size() != bilinear_it_new.size());
+
+    int ib1 = 0;
+    int ib2 = 0;
+
+    for(size_t i = 0; i < bilinear_ix.size(); ++i)
+    {
+        int ixval = bilinear_ix[i];
+        int iyval = bilinear_iy[i];
+        int ival  = bilinear_it_old[i];
+        int jval  = bilinear_it_new[i];
+
+        const int diff = jval - ival;
+
+        ib1 += diff * ixval;
+        ib2 += diff * iyval;
+    }
+
+    const double b1 = ib1 * FLT_SCALE;
+    const double b2 = ib2 * FLT_SCALE;
+
+    return std::make_tuple(b1, b2);
+}
+} // namespace
+
+template <typename T>
+std::vector<KeyPoint> optical_flow(const SimpleTensor<T> &old_input, const SimpleTensor<T> &new_input,
+                                   const OpticalFlowParameters &params, size_t num_levels,
+                                   const std::vector<KeyPoint> &old_points, const std::vector<KeyPoint> &new_points_estimates,
+                                   BorderMode border_mode, uint8_t constant_border_value)
+{
+    const int    filter_size      = 3;    // scharr filter size
+    const size_t max_iterations   = 1000; // fixed by kernel
+    const size_t window_dimension = params.window_dimension;
+    const size_t num_iterations   = (params.termination == Termination::TERM_CRITERIA_EPSILON) ? max_iterations : params.num_iterations;
+
+    KeyPointArray new_points(old_points.size());
+
+    InternalKeyPointArray old_points_internal = create_internal_keypoints(old_points);
+    InternalKeyPointArray new_points_internal = create_internal_keypoints(new_points_estimates);
+
+    SimpleTensor<int16_t> scharr_gx;
+    SimpleTensor<int16_t> scharr_gy;
+
+    // Create pyramids
+    std::vector<SimpleTensor<T>> old_pyramid = gaussian_pyramid_half(old_input, border_mode, constant_border_value, num_levels);
+    std::vector<SimpleTensor<T>> new_pyramid = gaussian_pyramid_half(new_input, border_mode, constant_border_value, num_levels);
+
+    // Iterate over each level of the pyramid
+    for(size_t idx = num_levels; idx > 0; --idx)
+    {
+        const size_t level = idx - 1;
+
+        // Calculate scharr gradients
+        std::tie(scharr_gx, scharr_gy) = scharr<int16_t, T>(old_pyramid[level], filter_size, border_mode, constant_border_value, GradientDimension::GRAD_XY);
+
+        scale_tracked_points(level, num_levels, params.use_initial_estimate, old_points_internal, new_points_internal, old_points, new_points_estimates);
+
+        // Calculate valid region based on image dimensions of current pyramid level
+        const ValidRegion valid_region = shape_to_valid_region(old_pyramid[level].shape(), (border_mode == BorderMode::UNDEFINED), BorderSize(filter_size / 2));
+
+        for(size_t i = 0; i < old_points.size(); ++i)
+        {
+            InternalKeyPoint &old_keypoint = old_points_internal.at(i);
+            InternalKeyPoint &new_keypoint = new_points_internal.at(i);
+
+            // Helper function for untracking keypoints when on the lowest pyramid level (high resolution)
+            const auto untrack_keypoint = [&](bool predicate)
+            {
+                if(predicate && (level == 0))
+                {
+                    new_keypoint.tracking_status = false;
+                    return true;
+                }
+                return predicate;
+            };
+
+            if(!old_keypoint.tracking_status)
+            {
+                continue;
+            }
+
+            // Check if tracked coordinate is outside image coordinate
+            if(untrack_keypoint(is_invalid_keypoint(old_keypoint, valid_region, window_dimension)))
+            {
+                continue;
+            }
+
+            // Compute spatial derivative
+            std::vector<int> bilinear_ix = compute_derivative(scharr_gx, old_keypoint, border_mode, constant_border_value, window_dimension, W_BITS);
+            std::vector<int> bilinear_iy = compute_derivative(scharr_gy, old_keypoint, border_mode, constant_border_value, window_dimension, W_BITS);
+
+            float A11 = 0.f;
+            float A12 = 0.f;
+            float A22 = 0.f;
+            std::tie(A11, A12, A22) = compute_spatial_gradient_matrix(bilinear_ix, bilinear_iy);
+
+            // Calculate criteria for lost tracking : Matrix A is invertible
+            // 1. The determinant of the matrix is less than DETERMINANT_THRESHOLD
+            // 2. The minimum eigenvalue of the matrix is less than EIGENVALUE_THRESHOLD
+            const float trace_A      = A11 + A22;
+            const float determinant  = A11 * A22 - A12 * A12;
+            const float discriminant = (trace_A * trace_A) - 4.0f * (determinant);
+            const float eigenvalue_A = (trace_A - std::sqrt(discriminant)) / 2.0f;
+
+            // Divide by window_dimension squared to reduce the floating point accummulation error
+            const float eigenvalue = eigenvalue_A / (window_dimension * window_dimension);
+
+            // Check if it is a good point to track
+            if(untrack_keypoint(eigenvalue < EIGENVALUE_THRESHOLD || determinant < DETERMINANT_THRESHOLD))
+            {
+                continue;
+            }
+
+            float prev_delta_x = 0.f;
+            float prev_delta_y = 0.f;
+
+            for(size_t j = 0; j < num_iterations; ++j)
+            {
+                // Check if tracked coordinate is outside image coordinate
+                if(untrack_keypoint(is_invalid_keypoint(new_keypoint, valid_region, window_dimension)))
+                {
+                    break;
+                }
+
+                // Compute temporal derivative
+                std::vector<int> bilinear_it_old = compute_derivative(old_pyramid[level], old_keypoint, border_mode, constant_border_value, window_dimension, W_BITS - 5);
+                std::vector<int> bilinear_it_new = compute_derivative(new_pyramid[level], new_keypoint, border_mode, constant_border_value, window_dimension, W_BITS - 5);
+
+                double b1 = 0.f;
+                double b2 = 0.f;
+                std::tie(b1, b2) = compute_temporal_gradient_vector(bilinear_it_old, bilinear_it_new, bilinear_ix, bilinear_iy);
+
+                // Compute motion vector -> A^-1 * -b
+                const float delta_x = (A12 * b2 - A22 * b1) / determinant;
+                const float delta_y = (A12 * b1 - A11 * b2) / determinant;
+
+                // Update the new position
+                new_keypoint.x += delta_x;
+                new_keypoint.y += delta_y;
+
+                const float magnitude_squared = delta_x * delta_x + delta_y * delta_y;
+
+                // Check if termination criteria is EPSILON and if it is satisfied
+                if(magnitude_squared <= params.epsilon && (params.termination == Termination::TERM_CRITERIA_EPSILON || params.termination == Termination::TERM_CRITERIA_BOTH))
+                {
+                    break;
+                }
+
+                // Check convergence analyzing the previous delta
+                if(j > 0 && (std::fabs(delta_x + prev_delta_x) < 0.01f && std::fabs(delta_y + prev_delta_y) < 0.01f))
+                {
+                    new_keypoint.x -= delta_x * SCALE_PYRAMID_HALF;
+                    new_keypoint.y -= delta_y * SCALE_PYRAMID_HALF;
+
+                    break;
+                }
+
+                prev_delta_x = delta_x;
+                prev_delta_y = delta_y;
+            }
+        }
+    }
+
+    // Copy optical flow coordinates to output vector
+    for(size_t i = 0; i < old_points.size(); ++i)
+    {
+        const InternalKeyPoint &new_keypoint = new_points_internal.at(i);
+
+        new_points.at(i).x               = roundf(new_keypoint.x);
+        new_points.at(i).y               = roundf(new_keypoint.y);
+        new_points.at(i).tracking_status = new_keypoint.tracking_status ? 1 : 0;
+    }
+
+    return new_points;
+}
+
+template std::vector<KeyPoint> optical_flow(const SimpleTensor<uint8_t> &old_input, const SimpleTensor<uint8_t> &new_input,
+                                            const OpticalFlowParameters &params, size_t num_levels,
+                                            const std::vector<KeyPoint> &old_points, const std::vector<KeyPoint> &new_points_estimates,
+                                            BorderMode border_mode, uint8_t constant_border_value);
+} // namespace reference
+} // namespace validation
+} // namespace test
+} // namespace arm_compute
diff --git a/tests/validation/reference/OpticalFlow.h b/tests/validation/reference/OpticalFlow.h
new file mode 100644
index 0000000000..ad6e2a92b6
--- /dev/null
+++ b/tests/validation/reference/OpticalFlow.h
@@ -0,0 +1,49 @@
+/*
+ * Copyright (c) 2018 ARM Limited.
+ *
+ * SPDX-License-Identifier: MIT
+ *
+ * Permission is hereby granted, free of charge, to any person obtaining a copy
+ * of this software and associated documentation files (the "Software"), to
+ * deal in the Software without restriction, including without limitation the
+ * rights to use, copy, modify, merge, publish, distribute, sublicense, and/or
+ * sell copies of the Software, and to permit persons to whom the Software is
+ * furnished to do so, subject to the following conditions:
+ *
+ * The above copyright notice and this permission notice shall be included in all
+ * copies or substantial portions of the Software.
+ *
+ * THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
+ * IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
+ * FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE
+ * AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
+ * LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM,
+ * OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN THE
+ * SOFTWARE.
+ */
+#ifndef __ARM_COMPUTE_TEST_OPTICAL_FLOW_H__
+#define __ARM_COMPUTE_TEST_OPTICAL_FLOW_H__
+
+#include "tests/SimpleTensor.h"
+#include "tests/Types.h"
+
+#include <vector>
+
+namespace arm_compute
+{
+namespace test
+{
+namespace validation
+{
+namespace reference
+{
+template <typename T>
+std::vector<KeyPoint> optical_flow(const SimpleTensor<T> &old_input, const SimpleTensor<T> &new_input,
+                                   const OpticalFlowParameters &params, size_t num_levels,
+                                   const std::vector<KeyPoint> &old_points, const std::vector<KeyPoint> &new_points_estimates,
+                                   BorderMode border_mode, uint8_t constant_border_value);
+} // namespace reference
+} // namespace validation
+} // namespace test
+} // namespace arm_compute
+#endif /* __ARM_COMPUTE_TEST_OPTICAL_FLOW_H__ */
diff --git a/utils/TypePrinter.h b/utils/TypePrinter.h
index e26b695809..c2de2a7e58 100644
--- a/utils/TypePrinter.h
+++ b/utils/TypePrinter.h
@@ -1458,7 +1458,13 @@ inline std::string to_string(const GPUTarget &gpu_target)
     return str.str();
 }
 
-/** Formatted output of the DetectionWindow type. */
+/** Formatted output of the DetectionWindow type.
+ *
+ * @param[out] os               Output stream
+ * @param[in]  detection_window Type to output
+ *
+ * @return Modified output stream.
+ */
 inline ::std::ostream &operator<<(::std::ostream &os, const DetectionWindow &detection_window)
 {
     os << "{x=" << detection_window.x << ","
@@ -1471,6 +1477,59 @@ inline ::std::ostream &operator<<(::std::ostream &os, const DetectionWindow &det
     return os;
 }
 
+/** Formatted output of the DetectionWindow type.
+ *
+ * @param[in] detection_window Type to output
+ *
+ * @return Formatted string.
+ */
+inline std::string to_string(const DetectionWindow &detection_window)
+{
+    std::stringstream str;
+    str << detection_window;
+    return str.str();
+}
+
+/** Formatted output of the Termination type.
+ *
+ * @param[out] os          Output stream
+ * @param[in]  termination Type to output
+ *
+ * @return Modified output stream.
+ */
+inline ::std::ostream &operator<<(::std::ostream &os, const Termination &termination)
+{
+    switch(termination)
+    {
+        case Termination::TERM_CRITERIA_EPSILON:
+            os << "TERM_CRITERIA_EPSILON";
+            break;
+        case Termination::TERM_CRITERIA_ITERATIONS:
+            os << "TERM_CRITERIA_ITERATIONS";
+            break;
+        case Termination::TERM_CRITERIA_BOTH:
+            os << "TERM_CRITERIA_BOTH";
+            break;
+        default:
+            ARM_COMPUTE_ERROR("NOT_SUPPORTED!");
+    }
+
+    return os;
+}
+
+/** Formatted output of the Termination type.
+ *
+ * @param[in] termination Type to output
+ *
+ * @return Formatted string.
+ */
+inline std::string to_string(const Termination &termination)
+{
+    std::stringstream str;
+    str << termination;
+    return str.str();
+}
+
 /** Formatted output of the WinogradInfo type. */
 inline ::std::ostream &operator<<(::std::ostream &os, const WinogradInfo &info)
 {
@@ -1482,13 +1541,6 @@ inline ::std::ostream &operator<<(::std::ostream &os, const WinogradInfo &info)
     return os;
 }
 
-inline std::string to_string(const DetectionWindow &type)
-{
-    std::stringstream str;
-    str << type;
-    return str.str();
-}
-
 inline std::string to_string(const WinogradInfo &type)
 {
     std::stringstream str;
@@ -1496,4 +1548,4 @@ inline std::string to_string(const WinogradInfo &type)
     return str.str();
 }
 } // namespace arm_compute
-#endif /* __ARM_COMPUTE_TEST_TYPE_PRINTER_H__ */
\ No newline at end of file
+#endif /* __ARM_COMPUTE_TEST_TYPE_PRINTER_H__ */