1_parallel_for.h

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#pragma once
 
#include <vector>
 
#include "gts/micro_scheduler/WorkerPool.h"
#include "gts/micro_scheduler/MicroScheduler.h"
#include "gts/micro_scheduler/patterns/ParallelFor.h"
#include "gts/micro_scheduler/patterns/Partitioners.h"
#include "gts/micro_scheduler/patterns/Range1d.h"
 
using namespace gts;
 
namespace gts_examples {
 
//------------------------------------------------------------------------------
void simplestIndexedParallelFor()
{
    printf ("================\n");
    printf ("simplestIndexedParallelFor\n");
    printf ("================\n");
 
    // Demonstrates the simplest ParallelFor interface with 
    // iteration over a container using an index.
 
    // Init boilerplate
    WorkerPool workerPool;
    bool result = workerPool.initialize();
    GTS_ASSERT(result);
    MicroScheduler microScheduler;
    result = microScheduler.initialize(&workerPool);
    GTS_ASSERT(result);
 
    size_t const elementCount = 1 << 16;
 
    // Make a ParallelFor object for this scheduler. We do this because
    // there can be multiple scheduler objects.
    ParallelFor parFor(microScheduler);
 
    // Increment a vector of items in parallel
    std::vector<int> vec(elementCount, 0);
    parFor(size_t(0), size_t(vec.size()), [&vec](size_t idx) { vec[idx]++; });
 
    // Verify results.
    for (auto const& v : vec)
    {
        GTS_ASSERT(v == 1);
    }
}
 
//------------------------------------------------------------------------------
void simplerIteratorParallelFor()
{
    printf ("================\n");
    printf ("simplerIteratorParallelFor\n");
    printf ("================\n");
 
    // Demonstrates the simpler ParallelFor interface with 
    // iteration over a container using an iterator.
 
    // Init boilerplate
    WorkerPool workerPool;
    bool result = workerPool.initialize();
    GTS_ASSERT(result);
    MicroScheduler microScheduler;
    result = microScheduler.initialize(&workerPool);
    GTS_ASSERT(result);
 
    size_t const elementCount = 1 << 16;
 
    ParallelFor parFor(microScheduler);
 
    // The partitioner determines how the data in Range1d is divided
    // up over all the works. AdaptivePartitioner type only divides when
    // other worker threads need more work.
    auto partitionerType = AdaptivePartitioner();
 
    // Since the partitioner is adaptive, a block size of 1 gives the partitioner
    // full control over division.
    size_t const blockSize = 1;
 
    // Increment a vector of items in parallel
    std::vector<int> vec(elementCount, 0);
    parFor(
        vec.begin(),
        vec.end(),
        [](std::vector<int>::iterator iter) { (*iter)++; });
 
    // Verify results.
    for (auto const& v : vec)
    {
        GTS_ASSERT(v == 1);
    }
}
 
//------------------------------------------------------------------------------
void fullParallelFor()
{
    printf ("================\n");
    printf ("fullParallelFor\n");
    printf ("================\n");
 
    // Demonstrates the full ParallelFor interface. Note that the ParallelFor
    // execution function gives full access to the iteration range.
 
    // Init boilerplate
    WorkerPool workerPool;
    bool result = workerPool.initialize();
    GTS_ASSERT(result);
    MicroScheduler microScheduler;
    result = microScheduler.initialize(&workerPool);
    GTS_ASSERT(result);
 
    size_t const elementCount = 1 << 16;
    std::vector<int> vec(elementCount, 0);
 
    ParallelFor parallelFor(microScheduler);
    auto partitionerType = AdaptivePartitioner();
    size_t const blockSize = 1;
 
    parallelFor(
 
        // The 1D index range parallel-for will iterate over.
        Range1d<size_t>(0, elementCount, blockSize),
 
        // The function parallel for will execute on each block of the range.
        [](Range1d<size_t>& range, void* pData, TaskContext const&)
        {
            // unpack the user data
            std::vector<int>& vec = *(std::vector<int>*)pData;
 
            // For each index in the block, increment the element.
            for (size_t idx = range.begin(); idx != range.end(); ++idx)
            {
                vec[idx]++;
            }
        },
 
        // The partitioner object.
        partitionerType,
 
        // The vec user data.
        &vec
    );
 
    // Verify results.
    for (auto const& v : vec)
    {
        GTS_ASSERT(v == 1);
    }
}
 
} // namespace gts_examples