ArrayFire example to split work across multiple GPUs - No threads Used.

multigpu-no-threads.cpp

/*******************************************************
 * Copyright (c) 2017, ArrayFire
 * All rights reserved.
 *
 * This file is distributed under 3-clause BSD license.
 * The complete license agreement can be obtained at:
 * http://arrayfire.com/licenses/BSD-3-Clause
 ********************************************************/

#include <arrayfire.h>
#include <chrono>

using namespace af;

using std::vector;
using std::string;

int main(void)
{
    vector<bool> isDilationFlags;
    vector<bool> isColorFlags;
    vector<string> files;

    files.push_back( string("<path to image file>") );
    isDilationFlags.push_back(true);
    isColorFlags.push_back(false);

    files.push_back( string("<path to image file>") );
    isDilationFlags.push_back(false);
    isColorFlags.push_back(true);

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

    for(int pos = 0; pos<files.size(); ++pos)
    {
        const bool isDilation = isDilationFlags[pos];
        const bool isColor    = isColorFlags[pos];

        const dim4 maskdims(3,3,1,1);

        // Need to set the device before data is created or
        // loaded onto the memory of the GPU to which
        // work has to be submitted
        int trgtDeviceId = pos % af::getDeviceCount();

        af::setDevice(trgtDeviceId);
       
        const array mask = constant(1.0, maskdims);

        // af::loadImage is blocking call since it loads
        // data from disk to GPU memory
        array input = loadImage(files[pos].c_str(), isColor);

        // all function calls in ArrayFire are asynchronous in nature
        // unless they are copying data to or from GPU
        af::array out = isDilation ? dilate(input, mask) : erode(input, mask);
      
        // Process the next image: files[pos+1]
    }

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

    std::chrono::duration<double> diff = end - start;

    std::cout << "Total time taken for test : " << diff.count() << " s\n";
    
    return 0;
}