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#pragma once
#include "LargeBuffer.h"
namespace CpuCompute
{
// Callback interface for the parallel `for`
__interface iComputeRange
{
// The implementation calls this method on multiple thread pool threads in parallel, and aggregates status codes.
HRESULT __stdcall compute( size_t begin, size_t end ) const;
};
// Similar to ThreadPoolWork in parallelFor.h, optimized to be used as a direct replacement of OpenMP pool.
class alignas( 64 ) ParallelForRunner
{
public:
ParallelForRunner( int threads );
~ParallelForRunner();
HRESULT setThreadsCount( int threads );
HRESULT parallelFor( iComputeRange& compute, size_t length, size_t minBatch = 1 );
// Allocate a temporary buffer for the calling thread.
// The pointer is guaranteed to be aligned by page size = 4kb
void* threadLocalBuffer( size_t cb );
private:
int maxThreads;
PTP_WORK work = nullptr;
iComputeRange* computeRange = nullptr;
size_t countItems = 0;
size_t countThreads = 0;
// Aligning by cache lines.
// Avoiding cache line sharing between CPU cores improves performance, despite wasting a few bytes of memory.
struct alignas( 64 ) ThreadBuffer
{
LargeBuffer memory;
size_t cb = 0;
};
std::vector<ThreadBuffer> threadBuffers;
alignas( 64 ) volatile long threadIndex = 0;
volatile HRESULT status = S_OK;
void runBatch( size_t ith ) noexcept;
static void __stdcall workCallbackStatic( PTP_CALLBACK_INSTANCE Instance, void* pv, PTP_WORK Work ) noexcept;
};
}
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