Skip to Main Content
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

Matrix Multiply

Example 11-6 shows a SerialMatrixMultiply that makes no use of Threading Building Blocks or any other parallelization, whereas Example 11-7 shows the corresponding ParallelMatrixMultiply that uses a blocked_range2d to specify a two-dimensional iteration space. The functions operate the same as far as the rest of the program is concerned. Obviously, we expect ParallelMatrixMultiply to run faster when on a machine with more than one processor core.

Example 11-6. Matrix multiply serial code

const size_t L = 150;
const size_t M = 225;
const size_t N = 300;

void SerialMatrixMultiply( float c[M][N], float a[M][L], float b[L][N] ) {
    for( size_t i=0; i<M; ++i ) {
        for( size_t j=0; j<N; ++j ) {
            float sum = 0;
            for( size_t k=0; k<L; ++k )
                sum += a[i][k]*b[k][j];
            c[i][j] = sum;
        }
    }
}

Example 11-7. Equivalent matrix multiply with blocked_range2d

#include "tbb/parallel_for.h" #include "tbb/blocked_range2d.h" using namespace tbb; const size_t L = 150; const size_t M = 225; const size_t N = 300; class MatrixMultiplyBody2D { float (*my_a)[L]; float (*my_b)[N]; float (*my_c)[N]; public: void operator()( const blocked_range2d<size_t>& r ) const { float (*a)[L] = my_a; // a,b,c used in example to emphasize float (*b)[N] = my_b; // commonality with serial code float (*c)[N] = my_c; for( size_t i=r.rows().begin(); i!=r.rows().end(); ++i ){ for( size_t j=r.cols().begin(); j!=r.cols().end(); ++j ) { float sum = 0; for( size_t k=0; k<L; ++k ) sum += a[i][k]*b[k][j]; c[i][j] = sum; } } } MatrixMultiplyBody2D( ...
Become an O’Reilly member and get unlimited access to this title plus top books and audiobooks from O’Reilly and nearly 200 top publishers, thousands of courses curated by job role, 150+ live events each month,
and much more.
Start your free trial

You might also like

Intel® Xeon Phi™ Coprocessor Architecture and Tools: The Guide for Application Developers

Intel® Xeon Phi™ Coprocessor Architecture and Tools: The Guide for Application Developers

Rezaur Rahman

Publisher Resources

ISBN: 9780596514808Errata Page