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<title>Level 1 GSL BLAS Interface - GNU Scientific Library -- Reference Manual</title>
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<p>
<a name="Level-1-GSL-BLAS-Interface"></a>
Next: <a rel="next" accesskey="n" href="Level-2-GSL-BLAS-Interface.html">Level 2 GSL BLAS Interface</a>,
Up: <a rel="up" accesskey="u" href="GSL-BLAS-Interface.html">GSL BLAS Interface</a>
<hr>
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<h4 class="subsection">12.1.1 Level 1</h4>
<div class="defun">
— Function: int <b>gsl_blas_sdsdot</b> (<var>float alpha, const gsl_vector_float * x, const gsl_vector_float * y, float * result</var>)<var><a name="index-gsl_005fblas_005fsdsdot-1077"></a></var><br>
<blockquote><p><a name="index-DOT_002c-Level_002d1-BLAS-1078"></a>This function computes the sum \alpha + x^T y for the vectors
<var>x</var> and <var>y</var>, returning the result in <var>result</var>. 
</p></blockquote></div>
<div class="defun">
— Function: int <b>gsl_blas_sdot</b> (<var>const gsl_vector_float * x, const gsl_vector_float * y, float * result</var>)<var><a name="index-gsl_005fblas_005fsdot-1079"></a></var><br>
— Function: int <b>gsl_blas_dsdot</b> (<var>const gsl_vector_float * x, const gsl_vector_float * y, double * result</var>)<var><a name="index-gsl_005fblas_005fdsdot-1080"></a></var><br>
— Function: int <b>gsl_blas_ddot</b> (<var>const gsl_vector * x, const gsl_vector * y, double * result</var>)<var><a name="index-gsl_005fblas_005fddot-1081"></a></var><br>
<blockquote><p>These functions compute the scalar product x^T y for the vectors
<var>x</var> and <var>y</var>, returning the result in <var>result</var>. 
</p></blockquote></div>
<div class="defun">
— Function: int <b>gsl_blas_cdotu</b> (<var>const gsl_vector_complex_float * x, const gsl_vector_complex_float * y, gsl_complex_float * dotu</var>)<var><a name="index-gsl_005fblas_005fcdotu-1082"></a></var><br>
— Function: int <b>gsl_blas_zdotu</b> (<var>const gsl_vector_complex * x, const gsl_vector_complex * y, gsl_complex * dotu</var>)<var><a name="index-gsl_005fblas_005fzdotu-1083"></a></var><br>
<blockquote><p>These functions compute the complex scalar product x^T y for the
vectors <var>x</var> and <var>y</var>, returning the result in <var>result</var>
</p></blockquote></div>
<div class="defun">
— Function: int <b>gsl_blas_cdotc</b> (<var>const gsl_vector_complex_float * x, const gsl_vector_complex_float * y, gsl_complex_float * dotc</var>)<var><a name="index-gsl_005fblas_005fcdotc-1084"></a></var><br>
— Function: int <b>gsl_blas_zdotc</b> (<var>const gsl_vector_complex * x, const gsl_vector_complex * y, gsl_complex * dotc</var>)<var><a name="index-gsl_005fblas_005fzdotc-1085"></a></var><br>
<blockquote><p>These functions compute the complex conjugate scalar product x^H
y for the vectors <var>x</var> and <var>y</var>, returning the result in
<var>result</var>
</p></blockquote></div>
<div class="defun">
— Function: float <b>gsl_blas_snrm2</b> (<var>const gsl_vector_float * x</var>)<var><a name="index-gsl_005fblas_005fsnrm2-1086"></a></var><br>
— Function: double <b>gsl_blas_dnrm2</b> (<var>const gsl_vector * x</var>)<var><a name="index-gsl_005fblas_005fdnrm2-1087"></a></var><br>
<blockquote><p><a name="index-NRM2_002c-Level_002d1-BLAS-1088"></a>These functions compute the Euclidean norm
<!-- {$||x||_2 = \sqrt{\sum x_i^2}$} -->
||x||_2 = \sqrt {\sum x_i^2} of the vector <var>x</var>. 
</p></blockquote></div>
<div class="defun">
— Function: float <b>gsl_blas_scnrm2</b> (<var>const gsl_vector_complex_float * x</var>)<var><a name="index-gsl_005fblas_005fscnrm2-1089"></a></var><br>
— Function: double <b>gsl_blas_dznrm2</b> (<var>const gsl_vector_complex * x</var>)<var><a name="index-gsl_005fblas_005fdznrm2-1090"></a></var><br>
<blockquote><p>These functions compute the Euclidean norm of the complex vector <var>x</var>,
     <pre class="example">          ||x||_2 = \sqrt {\sum (\Re(x_i)^2 + \Im(x_i)^2)}.
</pre>
        </blockquote></div>
<div class="defun">
— Function: float <b>gsl_blas_sasum</b> (<var>const gsl_vector_float * x</var>)<var><a name="index-gsl_005fblas_005fsasum-1091"></a></var><br>
— Function: double <b>gsl_blas_dasum</b> (<var>const gsl_vector * x</var>)<var><a name="index-gsl_005fblas_005fdasum-1092"></a></var><br>
<blockquote><p><a name="index-ASUM_002c-Level_002d1-BLAS-1093"></a>These functions compute the absolute sum \sum |x_i| of the
elements of the vector <var>x</var>. 
</p></blockquote></div>
<div class="defun">
— Function: float <b>gsl_blas_scasum</b> (<var>const gsl_vector_complex_float * x</var>)<var><a name="index-gsl_005fblas_005fscasum-1094"></a></var><br>
— Function: double <b>gsl_blas_dzasum</b> (<var>const gsl_vector_complex * x</var>)<var><a name="index-gsl_005fblas_005fdzasum-1095"></a></var><br>
<blockquote><p>These functions compute the sum of the magnitudes of the real and
imaginary parts of the complex vector <var>x</var>,
<!-- {$\sum \left( |\Re(x_i)| + |\Im(x_i)| \right)$} -->
\sum |\Re(x_i)| + |\Im(x_i)|. 
</p></blockquote></div>
<div class="defun">
— Function: CBLAS_INDEX_t <b>gsl_blas_isamax</b> (<var>const gsl_vector_float * x</var>)<var><a name="index-gsl_005fblas_005fisamax-1096"></a></var><br>
— Function: CBLAS_INDEX_t <b>gsl_blas_idamax</b> (<var>const gsl_vector * x</var>)<var><a name="index-gsl_005fblas_005fidamax-1097"></a></var><br>
— Function: CBLAS_INDEX_t <b>gsl_blas_icamax</b> (<var>const gsl_vector_complex_float * x</var>)<var><a name="index-gsl_005fblas_005ficamax-1098"></a></var><br>
— Function: CBLAS_INDEX_t <b>gsl_blas_izamax</b> (<var>const gsl_vector_complex * x</var>)<var><a name="index-gsl_005fblas_005fizamax-1099"></a></var><br>
<blockquote><p><a name="index-AMAX_002c-Level_002d1-BLAS-1100"></a>These functions return the index of the largest element of the vector
<var>x</var>. The largest element is determined by its absolute magnitude for
real vectors and by the sum of the magnitudes of the real and imaginary
parts |\Re(x_i)| + |\Im(x_i)| for complex vectors.  If the
largest value occurs several times then the index of the first
occurrence is returned. 
</p></blockquote></div>
<div class="defun">
— Function: int <b>gsl_blas_sswap</b> (<var>gsl_vector_float * x, gsl_vector_float * y</var>)<var><a name="index-gsl_005fblas_005fsswap-1101"></a></var><br>
— Function: int <b>gsl_blas_dswap</b> (<var>gsl_vector * x, gsl_vector * y</var>)<var><a name="index-gsl_005fblas_005fdswap-1102"></a></var><br>
— Function: int <b>gsl_blas_cswap</b> (<var>gsl_vector_complex_float * x, gsl_vector_complex_float * y</var>)<var><a name="index-gsl_005fblas_005fcswap-1103"></a></var><br>
— Function: int <b>gsl_blas_zswap</b> (<var>gsl_vector_complex * x, gsl_vector_complex * y</var>)<var><a name="index-gsl_005fblas_005fzswap-1104"></a></var><br>
<blockquote><p><a name="index-SWAP_002c-Level_002d1-BLAS-1105"></a>These functions exchange the elements of the vectors <var>x</var> and <var>y</var>. 
</p></blockquote></div>
<div class="defun">
— Function: int <b>gsl_blas_scopy</b> (<var>const gsl_vector_float * x, gsl_vector_float * y</var>)<var><a name="index-gsl_005fblas_005fscopy-1106"></a></var><br>
— Function: int <b>gsl_blas_dcopy</b> (<var>const gsl_vector * x, gsl_vector * y</var>)<var><a name="index-gsl_005fblas_005fdcopy-1107"></a></var><br>
— Function: int <b>gsl_blas_ccopy</b> (<var>const gsl_vector_complex_float * x, gsl_vector_complex_float * y</var>)<var><a name="index-gsl_005fblas_005fccopy-1108"></a></var><br>
— Function: int <b>gsl_blas_zcopy</b> (<var>const gsl_vector_complex * x, gsl_vector_complex * y</var>)<var><a name="index-gsl_005fblas_005fzcopy-1109"></a></var><br>
<blockquote><p><a name="index-COPY_002c-Level_002d1-BLAS-1110"></a>These functions copy the elements of the vector <var>x</var> into the vector
<var>y</var>. 
</p></blockquote></div>
<div class="defun">
— Function: int <b>gsl_blas_saxpy</b> (<var>float alpha, const gsl_vector_float * x, gsl_vector_float * y</var>)<var><a name="index-gsl_005fblas_005fsaxpy-1111"></a></var><br>
— Function: int <b>gsl_blas_daxpy</b> (<var>double alpha, const gsl_vector * x, gsl_vector * y</var>)<var><a name="index-gsl_005fblas_005fdaxpy-1112"></a></var><br>
— Function: int <b>gsl_blas_caxpy</b> (<var>const gsl_complex_float alpha, const gsl_vector_complex_float * x, gsl_vector_complex_float * y</var>)<var><a name="index-gsl_005fblas_005fcaxpy-1113"></a></var><br>
— Function: int <b>gsl_blas_zaxpy</b> (<var>const gsl_complex alpha, const gsl_vector_complex * x, gsl_vector_complex * y</var>)<var><a name="index-gsl_005fblas_005fzaxpy-1114"></a></var><br>
<blockquote><p><a name="index-AXPY_002c-Level_002d1-BLAS-1115"></a><a name="index-DAXPY_002c-Level_002d1-BLAS-1116"></a><a name="index-SAXPY_002c-Level_002d1-BLAS-1117"></a>These functions compute the sum y = \alpha x + y for the vectors
<var>x</var> and <var>y</var>. 
</p></blockquote></div>
<div class="defun">
— Function: void <b>gsl_blas_sscal</b> (<var>float alpha, gsl_vector_float * x</var>)<var><a name="index-gsl_005fblas_005fsscal-1118"></a></var><br>
— Function: void <b>gsl_blas_dscal</b> (<var>double alpha, gsl_vector * x</var>)<var><a name="index-gsl_005fblas_005fdscal-1119"></a></var><br>
— Function: void <b>gsl_blas_cscal</b> (<var>const gsl_complex_float alpha, gsl_vector_complex_float * x</var>)<var><a name="index-gsl_005fblas_005fcscal-1120"></a></var><br>
— Function: void <b>gsl_blas_zscal</b> (<var>const gsl_complex alpha, gsl_vector_complex * x</var>)<var><a name="index-gsl_005fblas_005fzscal-1121"></a></var><br>
— Function: void <b>gsl_blas_csscal</b> (<var>float alpha, gsl_vector_complex_float * x</var>)<var><a name="index-gsl_005fblas_005fcsscal-1122"></a></var><br>
— Function: void <b>gsl_blas_zdscal</b> (<var>double alpha, gsl_vector_complex * x</var>)<var><a name="index-gsl_005fblas_005fzdscal-1123"></a></var><br>
<blockquote><p><a name="index-SCAL_002c-Level_002d1-BLAS-1124"></a>These functions rescale the vector <var>x</var> by the multiplicative factor
<var>alpha</var>. 
</p></blockquote></div>
<div class="defun">
— Function: int <b>gsl_blas_srotg</b> (<var>float a</var>[]<var>, float b</var>[]<var>, float c</var>[]<var>, float s</var>[])<var><a name="index-gsl_005fblas_005fsrotg-1125"></a></var><br>
— Function: int <b>gsl_blas_drotg</b> (<var>double a</var>[]<var>, double b</var>[]<var>, double c</var>[]<var>, double s</var>[])<var><a name="index-gsl_005fblas_005fdrotg-1126"></a></var><br>
<blockquote><p><a name="index-ROTG_002c-Level_002d1-BLAS-1127"></a><a name="index-Givens-Rotation_002c-BLAS-1128"></a>These functions compute a Givens rotation (c,s) which zeroes the
vector (a,b),
     <pre class="example">          [  c  s ] [ a ] = [ r ]
          [ -s  c ] [ b ]   [ 0 ]
</pre>
        <p class="noindent">The variables <var>a</var> and <var>b</var> are overwritten by the routine. 
</p></blockquote></div>
<div class="defun">
— Function: int <b>gsl_blas_srot</b> (<var>gsl_vector_float * x, gsl_vector_float * y, float c, float s</var>)<var><a name="index-gsl_005fblas_005fsrot-1129"></a></var><br>
— Function: int <b>gsl_blas_drot</b> (<var>gsl_vector * x, gsl_vector * y, const double c, const double s</var>)<var><a name="index-gsl_005fblas_005fdrot-1130"></a></var><br>
<blockquote><p>These functions apply a Givens rotation (x', y') = (c x + s y, -s
x + c y) to the vectors <var>x</var>, <var>y</var>. 
</p></blockquote></div>
<div class="defun">
— Function: int <b>gsl_blas_srotmg</b> (<var>float d1</var>[]<var>, float d2</var>[]<var>, float b1</var>[]<var>, float b2, float P</var>[])<var><a name="index-gsl_005fblas_005fsrotmg-1131"></a></var><br>
— Function: int <b>gsl_blas_drotmg</b> (<var>double d1</var>[]<var>, double d2</var>[]<var>, double b1</var>[]<var>, double b2, double P</var>[])<var><a name="index-gsl_005fblas_005fdrotmg-1132"></a></var><br>
<blockquote><p><a name="index-Modified-Givens-Rotation_002c-BLAS-1133"></a><a name="index-Givens-Rotation_002c-Modified_002c-BLAS-1134"></a>These functions compute a modified Givens transformation.  The modified
Givens transformation is defined in the original Level-1 <span class="sc">blas</span>
specification, given in the references. 
</p></blockquote></div>
<div class="defun">
— Function: int <b>gsl_blas_srotm</b> (<var>gsl_vector_float * x, gsl_vector_float * y, const float P</var>[])<var><a name="index-gsl_005fblas_005fsrotm-1135"></a></var><br>
— Function: int <b>gsl_blas_drotm</b> (<var>gsl_vector * x, gsl_vector * y, const double P</var>[])<var><a name="index-gsl_005fblas_005fdrotm-1136"></a></var><br>
<blockquote><p>These functions apply a modified Givens transformation. 
</p></blockquote></div>
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