src/runtime/CL/CLTuner.cpp

/*
 * Copyright (c) 2017 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/CLTuner.h"

#include "arm_compute/core/CL/ICLKernel.h"
#include "arm_compute/runtime/CL/CLScheduler.h"

#include <chrono>
#include <limits>
#include <string>

using namespace arm_compute;

CLTuner::CLTuner()
    : _lws_table()
{
}

void CLTuner::tune_kernel(ICLKernel &kernel)
{
    // Get the configuration ID from the kernel
    const std::string &config_id = kernel.config_id();

    // Check if we need to find the Optimal LWS. If config_id is equal to default_config_id, the kernel does not require to be tuned
    if(config_id != arm_compute::default_config_id)
    {
        auto p = _lws_table.find(config_id);

        if(p == _lws_table.end())
        {
            // Find the optimal LWS for the kernel
            cl::NDRange opt_lws = find_optimal_lws(kernel);

            // Insert the optimal LWS in the table
            _lws_table.emplace(config_id, opt_lws);

            // Set Local-Workgroup-Size
            kernel.set_lws_hint(opt_lws);
        }
        else
        {
            // Set Local-Workgroup-Size
            kernel.set_lws_hint(p->second);
        }
    }
}

cl::NDRange CLTuner::find_optimal_lws(ICLKernel &kernel)
{
    cl::CommandQueue q = CLScheduler::get().queue();

    double min_exec_time = std::numeric_limits<double>::max();

    cl::NDRange opt_lws = cl::NDRange(1, 1);

    for(int y = 1; y <= 16; ++y)
    {
        for(int x = 1; x <= 16; ++x)
        {
            cl::NDRange lws_test = cl::NDRange(x, y);

            //Set the Local-Workgroup-Size
            kernel.set_lws_hint(lws_test);

            auto t_start = std::chrono::high_resolution_clock::now();

            // Run
            kernel.run(kernel.window(), q);

            CLScheduler::get().sync();

            auto t_stop = std::chrono::high_resolution_clock::now();

            std::chrono::duration<double, std::nano> fp_nano = t_stop - t_start;

            // Check the execution time
            if(fp_nano.count() < min_exec_time)
            {
                min_exec_time = fp_nano.count();
                opt_lws       = cl::NDRange(x, y);
            }
        }
    }

    return opt_lws;
}

void CLTuner::import_lws_table(const std::unordered_map<std::string, cl::NDRange> &lws_table)
{
    _lws_table.clear();
    _lws_table = lws_table;
}

const std::unordered_map<std::string, cl::NDRange> &CLTuner::export_lws_table()
{
    return _lws_table;
}