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Intel Threading Building Blocks
book

Intel Threading Building Blocks

by James Reinders
July 2007
Intermediate to advanced content levelIntermediate to advanced
332 pages
10h 4m
English
O'Reilly Media, Inc.
Content preview from Intel Threading Building Blocks

ParallelSum without Having to Specify a Grain Size

Example 11-20 does away with the need to supply a grain size by converting the prior example to use an auto_partitioner. Note how the block_range loses the grainsize parameter, and the parallel_reduce has a parameter added specifying our desire to use the auto_partitioner.

Example 11-20. ParallelSum with auto_partitioner

#include "tbb/parallel_reduce.h"
#include "tbb/blocked_range.h"

using namespace tbb;

struct Sum {
    float value;
    Sum() : value(0) {}
    Sum( Sum& s, split ) {value = 0;}
    void operator()( const blocked_range<float*>& range ) {
        float temp = value;
        for( float* a=range.begin(); a!=range.end(); ++a ) {
            temp += *a;
        }
        value = temp;
    }
    void join( Sum& rhs ) {value += rhs.value;}
};

float ParallelSum( float array[], size_t n ) {
    Sum total;
    parallel_reduce( blocked_range<float*>( array, array+n ),
                     total, auto_partitioner() );
    return total.value;
}
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Publisher Resources

ISBN: 9780596514808Errata Page