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<a name="BLAS-Examples"></a>
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Next: <a href="BLAS-References-and-Further-Reading.html#BLAS-References-and-Further-Reading" accesskey="n" rel="next">BLAS References and Further Reading</a>, Previous: <a href="GSL-BLAS-Interface.html#GSL-BLAS-Interface" accesskey="p" rel="previous">GSL BLAS Interface</a>, Up: <a href="BLAS-Support.html#BLAS-Support" accesskey="u" rel="up">BLAS Support</a> &nbsp; [<a href="Function-Index.html#Function-Index" title="Index" rel="index">Index</a>]</p>
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<a name="Examples-7"></a>
<h3 class="section">13.2 Examples</h3>

<p>The following program computes the product of two matrices using the
Level-3 <small>BLAS</small> function <small>DGEMM</small>,
</p>
<div class="example">
<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></div>

<p>The matrices are stored in row major order, according to the C convention 
for arrays.
</p>
<div class="example">
<pre class="verbatim">#include &lt;stdio.h&gt;
#include &lt;gsl/gsl_blas.h&gt;

int
main (void)
{
  double a[] = { 0.11, 0.12, 0.13,
                 0.21, 0.22, 0.23 };

  double b[] = { 1011, 1012,
                 1021, 1022,
                 1031, 1032 };

  double c[] = { 0.00, 0.00,
                 0.00, 0.00 };

  gsl_matrix_view A = gsl_matrix_view_array(a, 2, 3);
  gsl_matrix_view B = gsl_matrix_view_array(b, 3, 2);
  gsl_matrix_view C = gsl_matrix_view_array(c, 2, 2);

  /* Compute C = A B */

  gsl_blas_dgemm (CblasNoTrans, CblasNoTrans,
                  1.0, &amp;A.matrix, &amp;B.matrix,
                  0.0, &amp;C.matrix);

  printf (&quot;[ %g, %g\n&quot;, c[0], c[1]);
  printf (&quot;  %g, %g ]\n&quot;, c[2], c[3]);

  return 0;  
}
</pre></div>

<p>Here is the output from the program,
</p>
<div class="example">
<pre class="example">$ ./a.out
</pre><pre class="verbatim">[ 367.76, 368.12
  674.06, 674.72 ]
</pre></div>




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