Use look up table for fp16 activation

- Enables FP16 lut for logistic activation
- Adds LUTManager to re-use lut where appropriate.

Signed-off-by: Mohammed Suhail Munshi <MohammedSuhail.Munshi@arm.com>
Change-Id: I94667b63b452a8e58a1eb59cb0b5866178954523
Reviewed-on: https://review.mlplatform.org/c/ml/ComputeLibrary/+/10864
Tested-by: Arm Jenkins <bsgcomp@arm.com>
Reviewed-by: Gunes Bayir <gunes.bayir@arm.com>
Comments-Addressed: Arm Jenkins <bsgcomp@arm.com>
Benchmark: Arm Jenkins <bsgcomp@arm.com>

2 files changed, 145 insertions, 0 deletions

diff --git a/src/core/helpers/LUTManager.cpp b/src/core/helpers/LUTManager.cpp
new file mode 100644
index 0000000000..2bf0098118
--- /dev/null
+++ b/src/core/helpers/LUTManager.cpp
@@ -0,0 +1,72 @@
+/*
+ * Copyright (c) 2024 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 "src/core/helpers/LUTManager.h"
+
+namespace arm_compute
+{
+#ifdef __aarch64__
+namespace
+{
+void init_lut_fp16(ActivationLayerInfo::LookupTable65536 *lut)
+{
+    for (uint16_t i = 0; i < lut->size() - 1; ++i)
+    {
+        const float16_t *v = reinterpret_cast<float16_t *>(&i);
+        (*lut)[i]          = 1.f / (1.f + std::exp(-*v));
+    }
+    // Final value should be filled outside of loop to avoid overflows.
+    const uint16_t   i = lut->size() - 1;
+    const float16_t *v = reinterpret_cast<const float16_t *>(&i);
+    (*lut)[i]          = 1.f / (1.f + std::exp(-*v));
+}
+} // namespace
+
+std::shared_ptr<ActivationLayerInfo::LookupTable65536> LUTManager::get_lut_table(LUTInfo info)
+{
+    const auto itr = map_fp16.find(info);
+    if (itr != map_fp16.end() && !itr->second.expired())
+    {
+        // Found and valid
+        return itr->second.lock(); // Return weak ptr as shared ptr
+    }
+    else
+    {
+        // Not found, or pointer not valid
+        const auto ptr = std::make_shared<ActivationLayerInfo::LookupTable65536>();
+        init_lut_fp16(ptr.get());
+        map_fp16[info] = ptr;
+        return ptr;
+    }
+}
+#endif // __aarch64__
+
+// Static function to get LutManager instance
+LUTManager &LUTManager::get_instance()
+{
+    static auto inst_ = std::make_unique<LUTManager>(); // The one, single instance.
+    return *inst_;
+}
+
+} // namespace arm_compute
diff --git a/src/core/helpers/LUTManager.h b/src/core/helpers/LUTManager.h
new file mode 100644
index 0000000000..4e13ead7e3
--- /dev/null
+++ b/src/core/helpers/LUTManager.h
@@ -0,0 +1,73 @@
+/*
+ * Copyright (c) 2024 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 ACL_SRC_CORE_HELPERS_LUTMANAGER_H
+#define ACL_SRC_CORE_HELPERS_LUTMANAGER_H
+
+#include "arm_compute/core/CoreTypes.h"
+#include "arm_compute/core/QuantizationInfo.h"
+#include "arm_compute/function_info/ActivationLayerInfo.h"
+
+#include <map>
+#include <memory>
+
+namespace arm_compute
+{
+
+struct LUTInfo
+{
+    ActivationLayerInfo::ActivationFunction act;
+    DataType                                dt;
+    QuantizationInfo                        qinfo;
+    // Operators enable use of map with Lutinfo as key
+    friend bool operator<(const LUTInfo &l, const LUTInfo &r)
+    {
+        return (l.act < r.act) || ((l.act == r.act) && (l.dt < r.dt)) ||
+               ((l.act == r.act) && (l.dt == r.dt) && (l.qinfo.scale() < r.qinfo.scale())) ||
+               ((l.act == r.act) && (l.dt == r.dt) && (l.qinfo.scale() == r.qinfo.scale()) &&
+                (l.qinfo.offset() < l.qinfo.offset()));
+    }
+    bool operator==(const LUTInfo &l)
+    {
+        return this->act == l.act && this->dt == l.dt && this->qinfo == l.qinfo;
+    }
+};
+
+/* Class to handle getting look up table */
+class LUTManager
+{
+public:
+    LUTManager() = default;
+
+    static LUTManager &get_instance();
+#ifdef __aarch64__
+    std::shared_ptr<ActivationLayerInfo::LookupTable65536> get_lut_table(LUTInfo info);
+
+private:
+    std::map<LUTInfo, std::weak_ptr<ActivationLayerInfo::LookupTable65536>> map_fp16{};
+#endif // __aarch64__
+};
+
+} // namespace arm_compute
+#endif // ACL_SRC_CORE_HELPERS_LUTMANAGER_H