/*! @file izmax1.c * \brief Finds the index of the element whose real part has maximum absolute value * *
* -- LAPACK auxiliary routine (version 2.0) -- * Univ. of Tennessee, Univ. of California Berkeley, NAG Ltd., * Courant Institute, Argonne National Lab, and Rice University * October 31, 1992 **/ #include
Purpose ======= IZMAX1 finds the index of the element whose real part has maximum absolute value. Based on IZAMAX from Level 1 BLAS. The change is to use the 'genuine' absolute value. Contributed by Nick Higham for use with ZLACON. Arguments ========= N (input) INT The number of elements in the vector CX. CX (input) COMPLEX*16 array, dimension (N) The vector whose elements will be summed. INCX (input) INT The spacing between successive values of CX. INCX >= 1. =====================================================================*/ int izmax1_(int *n, doublecomplex *cx, int *incx) { /* System generated locals */ int ret_val, i__1, i__2; double d__1; /* Local variables */ double smax; int i, ix; #define CX(I) cx[(I)-1] ret_val = 0; if (*n < 1) { return ret_val; } ret_val = 1; if (*n == 1) { return ret_val; } if (*incx == 1) { goto L30; } /* CODE FOR INCREMENT NOT EQUAL TO 1 */ ix = 1; smax = (d__1 = CX(1).r, fabs(d__1)); ix += *incx; i__1 = *n; for (i = 2; i <= *n; ++i) { i__2 = ix; if ((d__1 = CX(ix).r, fabs(d__1)) <= smax) { goto L10; } ret_val = i; i__2 = ix; smax = (d__1 = CX(ix).r, fabs(d__1)); L10: ix += *incx; /* L20: */ } return ret_val; /* CODE FOR INCREMENT EQUAL TO 1 */ L30: smax = (d__1 = CX(1).r, fabs(d__1)); i__1 = *n; for (i = 2; i <= *n; ++i) { i__2 = i; if ((d__1 = CX(i).r, fabs(d__1)) <= smax) { goto L40; } ret_val = i; i__2 = i; smax = (d__1 = CX(i).r, fabs(d__1)); L40: ; } return ret_val; /* End of IZMAX1 */ } /* izmax1_ */