276 lines
7.3 KiB
C
276 lines
7.3 KiB
C
/* dsyr2.f -- translated by f2c (version 20061008).
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You must link the resulting object file with libf2c:
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on Microsoft Windows system, link with libf2c.lib;
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on Linux or Unix systems, link with .../path/to/libf2c.a -lm
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or, if you install libf2c.a in a standard place, with -lf2c -lm
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-- in that order, at the end of the command line, as in
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cc *.o -lf2c -lm
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Source for libf2c is in /netlib/f2c/libf2c.zip, e.g.,
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http://www.netlib.org/f2c/libf2c.zip
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*/
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#include "clapack.h"
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/* Subroutine */ int dsyr2_(char *uplo, integer *n, doublereal *alpha,
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doublereal *x, integer *incx, doublereal *y, integer *incy,
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doublereal *a, integer *lda)
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{
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/* System generated locals */
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integer a_dim1, a_offset, i__1, i__2;
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/* Local variables */
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integer i__, j, ix, iy, jx, jy, kx, ky, info;
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doublereal temp1, temp2;
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extern logical lsame_(char *, char *);
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extern /* Subroutine */ int xerbla_(char *, integer *);
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/* .. Scalar Arguments .. */
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/* .. */
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/* .. Array Arguments .. */
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/* .. */
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/* Purpose */
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/* ======= */
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/* DSYR2 performs the symmetric rank 2 operation */
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/* A := alpha*x*y' + alpha*y*x' + A, */
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/* where alpha is a scalar, x and y are n element vectors and A is an n */
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/* by n symmetric matrix. */
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/* Arguments */
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/* ========== */
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/* UPLO - CHARACTER*1. */
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/* On entry, UPLO specifies whether the upper or lower */
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/* triangular part of the array A is to be referenced as */
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/* follows: */
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/* UPLO = 'U' or 'u' Only the upper triangular part of A */
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/* is to be referenced. */
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/* UPLO = 'L' or 'l' Only the lower triangular part of A */
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/* is to be referenced. */
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/* Unchanged on exit. */
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/* N - INTEGER. */
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/* On entry, N specifies the order of the matrix A. */
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/* N must be at least zero. */
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/* Unchanged on exit. */
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/* ALPHA - DOUBLE PRECISION. */
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/* On entry, ALPHA specifies the scalar alpha. */
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/* Unchanged on exit. */
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/* X - DOUBLE PRECISION array of dimension at least */
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/* ( 1 + ( n - 1 )*abs( INCX ) ). */
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/* Before entry, the incremented array X must contain the n */
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/* element vector x. */
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/* Unchanged on exit. */
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/* INCX - INTEGER. */
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/* On entry, INCX specifies the increment for the elements of */
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/* X. INCX must not be zero. */
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/* Unchanged on exit. */
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/* Y - DOUBLE PRECISION array of dimension at least */
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/* ( 1 + ( n - 1 )*abs( INCY ) ). */
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/* Before entry, the incremented array Y must contain the n */
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/* element vector y. */
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/* Unchanged on exit. */
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/* INCY - INTEGER. */
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/* On entry, INCY specifies the increment for the elements of */
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/* Y. INCY must not be zero. */
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/* Unchanged on exit. */
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/* A - DOUBLE PRECISION array of DIMENSION ( LDA, n ). */
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/* Before entry with UPLO = 'U' or 'u', the leading n by n */
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/* upper triangular part of the array A must contain the upper */
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/* triangular part of the symmetric matrix and the strictly */
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/* lower triangular part of A is not referenced. On exit, the */
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/* upper triangular part of the array A is overwritten by the */
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/* upper triangular part of the updated matrix. */
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/* Before entry with UPLO = 'L' or 'l', the leading n by n */
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/* lower triangular part of the array A must contain the lower */
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/* triangular part of the symmetric matrix and the strictly */
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/* upper triangular part of A is not referenced. On exit, the */
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/* lower triangular part of the array A is overwritten by the */
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/* lower triangular part of the updated matrix. */
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/* LDA - INTEGER. */
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/* On entry, LDA specifies the first dimension of A as declared */
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/* in the calling (sub) program. LDA must be at least */
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/* max( 1, n ). */
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/* Unchanged on exit. */
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/* Level 2 Blas routine. */
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/* -- Written on 22-October-1986. */
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/* Jack Dongarra, Argonne National Lab. */
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/* Jeremy Du Croz, Nag Central Office. */
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/* Sven Hammarling, Nag Central Office. */
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/* Richard Hanson, Sandia National Labs. */
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/* .. Parameters .. */
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/* .. */
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/* .. Local Scalars .. */
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/* .. */
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/* .. External Functions .. */
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/* .. */
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/* .. External Subroutines .. */
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/* .. */
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/* .. Intrinsic Functions .. */
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/* .. */
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/* Test the input parameters. */
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/* Parameter adjustments */
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--x;
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--y;
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a_dim1 = *lda;
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a_offset = 1 + a_dim1;
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a -= a_offset;
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/* Function Body */
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info = 0;
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if (! lsame_(uplo, "U") && ! lsame_(uplo, "L")) {
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info = 1;
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} else if (*n < 0) {
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info = 2;
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} else if (*incx == 0) {
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info = 5;
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} else if (*incy == 0) {
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info = 7;
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} else if (*lda < max(1,*n)) {
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info = 9;
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}
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if (info != 0) {
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xerbla_("DSYR2 ", &info);
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return 0;
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}
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/* Quick return if possible. */
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if (*n == 0 || *alpha == 0.) {
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return 0;
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}
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/* Set up the start points in X and Y if the increments are not both */
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/* unity. */
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if (*incx != 1 || *incy != 1) {
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if (*incx > 0) {
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kx = 1;
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} else {
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kx = 1 - (*n - 1) * *incx;
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}
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if (*incy > 0) {
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ky = 1;
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} else {
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ky = 1 - (*n - 1) * *incy;
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}
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jx = kx;
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jy = ky;
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}
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/* Start the operations. In this version the elements of A are */
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/* accessed sequentially with one pass through the triangular part */
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/* of A. */
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if (lsame_(uplo, "U")) {
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/* Form A when A is stored in the upper triangle. */
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if (*incx == 1 && *incy == 1) {
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i__1 = *n;
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for (j = 1; j <= i__1; ++j) {
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if (x[j] != 0. || y[j] != 0.) {
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temp1 = *alpha * y[j];
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temp2 = *alpha * x[j];
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i__2 = j;
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for (i__ = 1; i__ <= i__2; ++i__) {
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a[i__ + j * a_dim1] = a[i__ + j * a_dim1] + x[i__] *
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temp1 + y[i__] * temp2;
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/* L10: */
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}
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}
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/* L20: */
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}
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} else {
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i__1 = *n;
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for (j = 1; j <= i__1; ++j) {
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if (x[jx] != 0. || y[jy] != 0.) {
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temp1 = *alpha * y[jy];
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temp2 = *alpha * x[jx];
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ix = kx;
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iy = ky;
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i__2 = j;
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for (i__ = 1; i__ <= i__2; ++i__) {
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a[i__ + j * a_dim1] = a[i__ + j * a_dim1] + x[ix] *
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temp1 + y[iy] * temp2;
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ix += *incx;
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iy += *incy;
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/* L30: */
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}
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}
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jx += *incx;
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jy += *incy;
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/* L40: */
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}
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}
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} else {
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/* Form A when A is stored in the lower triangle. */
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if (*incx == 1 && *incy == 1) {
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i__1 = *n;
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for (j = 1; j <= i__1; ++j) {
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if (x[j] != 0. || y[j] != 0.) {
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temp1 = *alpha * y[j];
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temp2 = *alpha * x[j];
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i__2 = *n;
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for (i__ = j; i__ <= i__2; ++i__) {
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a[i__ + j * a_dim1] = a[i__ + j * a_dim1] + x[i__] *
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temp1 + y[i__] * temp2;
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/* L50: */
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}
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}
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/* L60: */
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}
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} else {
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i__1 = *n;
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for (j = 1; j <= i__1; ++j) {
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if (x[jx] != 0. || y[jy] != 0.) {
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temp1 = *alpha * y[jy];
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temp2 = *alpha * x[jx];
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ix = jx;
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iy = jy;
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i__2 = *n;
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for (i__ = j; i__ <= i__2; ++i__) {
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a[i__ + j * a_dim1] = a[i__ + j * a_dim1] + x[ix] *
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temp1 + y[iy] * temp2;
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ix += *incx;
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iy += *incy;
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/* L70: */
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}
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}
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jx += *incx;
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jy += *incy;
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/* L80: */
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}
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}
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}
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return 0;
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/* End of DSYR2 . */
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} /* dsyr2_ */
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