114 lines
2.2 KiB
C
114 lines
2.2 KiB
C
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/*! @file izmax1.c
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* \brief Finds the index of the element whose real part has maximum absolute value
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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 <math.h>
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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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IZMAX1 finds the index of the element whose real part has maximum
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absolute value.
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Based on IZAMAX from 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 >= 1.
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=====================================================================
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</pre>
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*/
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int
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izmax1_(int *n, doublecomplex *cx, int *incx)
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{
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/* System generated locals */
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int ret_val, i__1, i__2;
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double d__1;
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/* Local variables */
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double smax;
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int i, ix;
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#define CX(I) cx[(I)-1]
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ret_val = 0;
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if (*n < 1) {
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return ret_val;
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}
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ret_val = 1;
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if (*n == 1) {
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return ret_val;
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}
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if (*incx == 1) {
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goto L30;
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}
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/* CODE FOR INCREMENT NOT EQUAL TO 1 */
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ix = 1;
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smax = (d__1 = CX(1).r, fabs(d__1));
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ix += *incx;
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i__1 = *n;
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for (i = 2; i <= *n; ++i) {
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i__2 = ix;
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if ((d__1 = CX(ix).r, fabs(d__1)) <= smax) {
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goto L10;
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}
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ret_val = i;
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i__2 = ix;
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smax = (d__1 = CX(ix).r, fabs(d__1));
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L10:
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ix += *incx;
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/* L20: */
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}
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return ret_val;
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/* CODE FOR INCREMENT EQUAL TO 1 */
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L30:
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smax = (d__1 = CX(1).r, fabs(d__1));
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i__1 = *n;
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for (i = 2; i <= *n; ++i) {
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i__2 = i;
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if ((d__1 = CX(i).r, fabs(d__1)) <= smax) {
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goto L40;
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}
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ret_val = i;
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i__2 = i;
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smax = (d__1 = CX(i).r, fabs(d__1));
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L40:
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;
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}
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return ret_val;
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/* End of IZMAX1 */
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} /* izmax1_ */
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