94 lines
1.9 KiB
C
94 lines
1.9 KiB
C
/*! @file dzsum1.c
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* \brief Takes sum of the absolute values of a complex vector and returns a double precision result
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*
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* <pre>
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* -- LAPACK auxiliary routine (version 2.0) --
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* Univ. of Tennessee, Univ. of California Berkeley, NAG Ltd.,
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* Courant Institute, Argonne National Lab, and Rice University
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* October 31, 1992
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* </pre>
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*/
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#include "slu_dcomplex.h"
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#include "slu_Cnames.h"
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/*! \brief
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<pre>
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Purpose
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=======
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DZSUM1 takes the sum of the absolute values of a complex
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vector and returns a double precision result.
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Based on DZASUM from the Level 1 BLAS.
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The change is to use the 'genuine' absolute value.
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Contributed by Nick Higham for use with ZLACON.
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Arguments
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=========
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N (input) INT
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The number of elements in the vector CX.
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CX (input) COMPLEX*16 array, dimension (N)
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The vector whose elements will be summed.
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INCX (input) INT
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The spacing between successive values of CX. INCX > 0.
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=====================================================================
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</pre>
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*/
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double dzsum1_(int *n, doublecomplex *cx, int *incx)
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{
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/* Builtin functions */
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double z_abs(doublecomplex *);
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/* Local variables */
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int i, nincx;
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double stemp;
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#define CX(I) cx[(I)-1]
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stemp = 0.;
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if (*n <= 0) {
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return stemp;
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}
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if (*incx == 1) {
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goto L20;
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}
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/* CODE FOR INCREMENT NOT EQUAL TO 1 */
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nincx = *n * *incx;
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for (i = 1; *incx < 0 ? i >= nincx : i <= nincx; i += *incx) {
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/* NEXT LINE MODIFIED. */
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stemp += z_abs(&CX(i));
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/* L10: */
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}
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return stemp;
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/* CODE FOR INCREMENT EQUAL TO 1 */
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L20:
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for (i = 1; i <= *n; ++i) {
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/* NEXT LINE MODIFIED. */
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stemp += z_abs(&CX(i));
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/* L30: */
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}
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return stemp;
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/* End of DZSUM1 */
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} /* dzsum1_ */
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