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>

5 files changed, 824 insertions, 0 deletions

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__ */