Abdelrahman Said
323 lines
8.7 KiB
C
323 lines
8.7 KiB
C
/* -- translated by f2c (version 20240504).
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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 "f2c.h"
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/* > \brief \b DSYR2
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=========== DOCUMENTATION ===========
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Online html documentation available at
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http://www.netlib.org/lapack/explore-html/
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Definition:
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===========
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SUBROUTINE DSYR2(UPLO,N,ALPHA,X,INCX,Y,INCY,A,LDA)
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DOUBLE PRECISION ALPHA
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INTEGER INCX,INCY,LDA,N
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CHARACTER UPLO
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DOUBLE PRECISION A(LDA,*),X(*),Y(*)
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> \par Purpose:
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=============
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>
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> \verbatim
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>
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> DSYR2 performs the symmetric rank 2 operation
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>
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> A := alpha*x*y**T + alpha*y*x**T + A,
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>
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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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> \endverbatim
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Arguments:
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==========
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> \param[in] UPLO
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> \verbatim
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> UPLO is 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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>
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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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>
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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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> \endverbatim
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>
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> \param[in] N
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> \verbatim
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> N is 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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> \endverbatim
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>
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> \param[in] ALPHA
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> \verbatim
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> ALPHA is DOUBLE PRECISION.
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> On entry, ALPHA specifies the scalar alpha.
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> \endverbatim
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>
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> \param[in] X
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> \verbatim
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> X is DOUBLE PRECISION array, 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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> \endverbatim
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>
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> \param[in] INCX
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> \verbatim
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> INCX is 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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> \endverbatim
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>
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> \param[in] Y
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> \verbatim
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> Y is DOUBLE PRECISION array, 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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> \endverbatim
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>
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> \param[in] INCY
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> \verbatim
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> INCY is 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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> \endverbatim
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>
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> \param[in,out] A
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> \verbatim
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> A is DOUBLE PRECISION array, 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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> \endverbatim
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>
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> \param[in] LDA
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> \verbatim
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> LDA is 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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> \endverbatim
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Authors:
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========
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> \author Univ. of Tennessee
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> \author Univ. of California Berkeley
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> \author Univ. of Colorado Denver
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> \author NAG Ltd.
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> \ingroup her2
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> \par Further Details:
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=====================
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>
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> \verbatim
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>
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> Level 2 Blas routine.
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>
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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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> \endverbatim
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>
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=====================================================================
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Subroutine */ int igraphdsyr2_(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 igraphlsame_(char *, char *);
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extern /* Subroutine */ int igraphxerbla_(char *, integer *, ftnlen);
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/* -- Reference BLAS level2 routine --
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-- Reference BLAS is a software package provided by Univ. of Tennessee, --
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-- Univ. of California Berkeley, Univ. of Colorado Denver and NAG Ltd..--
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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 (! igraphlsame_(uplo, "U") && ! igraphlsame_(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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igraphxerbla_("DSYR2 ", &info, (ftnlen)6);
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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 (igraphlsame_(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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} /* igraphdsyr2_ */
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