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<title>GSL CBLAS Examples - GNU Scientific Library -- Reference Manual</title>
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Previous: <a rel="previous" accesskey="p" href="Level-3-CBLAS-Functions.html">Level 3 CBLAS Functions</a>,
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<h3 class="section">D.4 Examples</h3>
<p>The following program computes the product of two matrices using the
Level-3 <span class="sc">blas</span> function <span class="sc">sgemm</span>,
<pre class="example"> [ 0.11 0.12 0.13 ] [ 1011 1012 ] [ 367.76 368.12 ]
[ 0.21 0.22 0.23 ] [ 1021 1022 ] = [ 674.06 674.72 ]
[ 1031 1032 ]
</pre>
<p class="noindent">The matrices are stored in row major order but could be stored in column
major order if the first argument of the call to <code>cblas_sgemm</code> was
changed to <code>CblasColMajor</code>.
<pre class="example"><pre class="verbatim"> #include <stdio.h>
#include <gsl/gsl_cblas.h>
int
main (void)
{
int lda = 3;
float A[] = { 0.11, 0.12, 0.13,
0.21, 0.22, 0.23 };
int ldb = 2;
float B[] = { 1011, 1012,
1021, 1022,
1031, 1032 };
int ldc = 2;
float C[] = { 0.00, 0.00,
0.00, 0.00 };
/* Compute C = A B */
cblas_sgemm (CblasRowMajor,
CblasNoTrans, CblasNoTrans, 2, 2, 3,
1.0, A, lda, B, ldb, 0.0, C, ldc);
printf ("[ %g, %g\n", C[0], C[1]);
printf (" %g, %g ]\n", C[2], C[3]);
return 0;
}
</pre></pre>
<p class="noindent">To compile the program use the following command line,
<pre class="example"> $ gcc -Wall demo.c -lgslcblas
</pre>
<p class="noindent">There is no need to link with the main library <code>-lgsl</code> in this
case as the <span class="sc">cblas</span> library is an independent unit. Here is the output
from the program,
<pre class="example"> $ ./a.out
<pre class="verbatim"> [ 367.76, 368.12
674.06, 674.72 ]
</pre></pre>
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