COMPMID-1796: Add support for ranged distribution.

Change-Id: I6347a02219bf47e21a29b9b5d1a9e7e23de8a502
Reviewed-on: https://review.mlplatform.org/482
Reviewed-by: Michele Di Giorgio <michele.digiorgio@arm.com>
Tested-by: Arm Jenkins <bsgcomp@arm.com>

1 files changed, 98 insertions, 0 deletions

diff --git a/arm_compute/core/utils/misc/Random.h b/arm_compute/core/utils/misc/Random.h
new file mode 100644
index 0000000000..4c40f5c2d7
--- /dev/null
+++ b/arm_compute/core/utils/misc/Random.h
@@ -0,0 +1,98 @@
+/*
+ * Copyright (c) 2019 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_MISC_RANDOM_H__
+#define __ARM_COMPUTE_MISC_RANDOM_H__
+
+#include "arm_compute/core/Error.h"
+
+#include <random>
+#include <type_traits>
+
+namespace arm_compute
+{
+namespace utils
+{
+namespace random
+{
+/** Uniform distribution within a given number of sub-ranges
+ *
+ * @tparam T Distribution primitive type
+ */
+template <typename T>
+class RangedUniformDistribution
+{
+public:
+    using DT = typename std::conditional<std::is_integral<T>::value,
+          std::uniform_int_distribution<T>,
+          std::uniform_real_distribution<float>>::type;
+    using result_type = T;
+    using range_pair  = std::pair<result_type, result_type>;
+
+public:
+    /** Constructor
+     *
+     * @param[in] low            lowest value in the range (inclusive)
+     * @param[in] high           highest value in the range (inclusive for uniform_int_distribution, exclusive for uniform_real_distribution)
+     * @param[in] exclude_ranges Ranges to exclude from the generator
+     */
+    RangedUniformDistribution(result_type low, result_type high, const std::vector<range_pair> &exclude_ranges)
+        : _distributions(), _selector()
+    {
+        result_type clow = low;
+        for(const auto &erange : exclude_ranges)
+        {
+            result_type epsilon = std::is_integral<result_type>::value ? 1 : static_cast<result_type>(std::numeric_limits<float>::epsilon());
+
+            ARM_COMPUTE_ERROR_ON(clow > erange.first || clow >= erange.second);
+
+            _distributions.emplace_back(DT(clow, erange.first - epsilon));
+            clow = erange.second + epsilon;
+        }
+        ARM_COMPUTE_ERROR_ON(clow > high);
+        _distributions.emplace_back(DT(clow, high));
+        _selector = std::uniform_int_distribution<uint32_t>(0, _distributions.size() - 1);
+    }
+    /** Generate random number
+     *
+     * @tparam URNG Random number generator object type
+     *
+     * @param[in] g A uniform random number generator object, used as the source of randomness.
+     *
+     * @return A new random number.
+     */
+    template <class URNG>
+    result_type operator()(URNG &g)
+    {
+        unsigned int rand_select = _selector(g);
+        return _distributions[rand_select](g);
+    }
+
+private:
+    std::vector<DT>                         _distributions;
+    std::uniform_int_distribution<uint32_t> _selector;
+};
+} // namespace random
+} // namespace utils
+} // namespace arm_compute
+#endif /* __ARM_COMPUTE_MISC_RANDOM_H__ */