Add graph references
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Abdelrahman Said
+384
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/* -- 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 DTRSV
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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 DTRSV(UPLO,TRANS,DIAG,N,A,LDA,X,INCX)
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INTEGER INCX,LDA,N
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CHARACTER DIAG,TRANS,UPLO
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DOUBLE PRECISION A(LDA,*),X(*)
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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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> DTRSV solves one of the systems of equations
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>
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> A*x = b, or A**T*x = b,
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>
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> where b and x are n element vectors and A is an n by n unit, or
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> non-unit, upper or lower triangular matrix.
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>
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> No test for singularity or near-singularity is included in this
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> routine. Such tests must be performed before calling this routine.
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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 matrix is an upper or
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> lower triangular matrix as follows:
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>
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> UPLO = 'U' or 'u' A is an upper triangular matrix.
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>
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> UPLO = 'L' or 'l' A is a lower triangular matrix.
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> \endverbatim
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>
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> \param[in] TRANS
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> \verbatim
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> TRANS is CHARACTER*1
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> On entry, TRANS specifies the equations to be solved as
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> follows:
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>
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> TRANS = 'N' or 'n' A*x = b.
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>
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> TRANS = 'T' or 't' A**T*x = b.
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>
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> TRANS = 'C' or 'c' A**T*x = b.
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> \endverbatim
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>
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> \param[in] DIAG
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> \verbatim
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> DIAG is CHARACTER*1
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> On entry, DIAG specifies whether or not A is unit
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> triangular as follows:
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>
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> DIAG = 'U' or 'u' A is assumed to be unit triangular.
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>
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> DIAG = 'N' or 'n' A is not assumed to be unit
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> triangular.
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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] 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 matrix and the strictly lower triangular part of
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> A is not referenced.
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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 matrix and the strictly upper triangular part of
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> A is not referenced.
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> Note that when DIAG = 'U' or 'u', the diagonal elements of
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> A are not referenced either, but are assumed to be unity.
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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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>
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> \param[in,out] 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 right-hand side vector b. On exit, X is overwritten
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> with the solution 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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>
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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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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 trsv
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=====================================================================
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Subroutine */ int igraphdtrsv_(char *uplo, char *trans, char *diag, integer *n,
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doublereal *a, integer *lda, doublereal *x, integer *incx)
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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, jx, kx, info;
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doublereal temp;
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extern logical igraphlsame_(char *, char *);
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extern /* Subroutine */ int igraphxerbla_(char *, integer *, ftnlen);
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logical nounit;
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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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a_dim1 = *lda;
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a_offset = 1 + a_dim1;
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a -= a_offset;
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--x;
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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 (! igraphlsame_(trans, "N") && ! igraphlsame_(trans,
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"T") && ! igraphlsame_(trans, "C")) {
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info = 2;
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} else if (! igraphlsame_(diag, "U") && ! igraphlsame_(diag,
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"N")) {
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info = 3;
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} else if (*n < 0) {
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info = 4;
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} else if (*lda < max(1,*n)) {
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info = 6;
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} else if (*incx == 0) {
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info = 8;
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}
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if (info != 0) {
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igraphxerbla_("DTRSV ", &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) {
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return 0;
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}
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nounit = igraphlsame_(diag, "N");
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/* Set up the start point in X if the increment is not unity. This
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will be ( N - 1 )*INCX too small for descending loops. */
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if (*incx <= 0) {
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kx = 1 - (*n - 1) * *incx;
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} else if (*incx != 1) {
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kx = 1;
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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 A. */
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if (igraphlsame_(trans, "N")) {
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/* Form x := inv( A )*x. */
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if (igraphlsame_(uplo, "U")) {
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if (*incx == 1) {
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for (j = *n; j >= 1; --j) {
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if (x[j] != 0.) {
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if (nounit) {
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x[j] /= a[j + j * a_dim1];
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}
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temp = x[j];
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for (i__ = j - 1; i__ >= 1; --i__) {
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x[i__] -= temp * a[i__ + j * a_dim1];
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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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jx = kx + (*n - 1) * *incx;
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for (j = *n; j >= 1; --j) {
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if (x[jx] != 0.) {
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if (nounit) {
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x[jx] /= a[j + j * a_dim1];
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}
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temp = x[jx];
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ix = jx;
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for (i__ = j - 1; i__ >= 1; --i__) {
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ix -= *incx;
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x[ix] -= temp * a[i__ + j * a_dim1];
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/* L30: */
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}
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}
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jx -= *incx;
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/* L40: */
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}
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}
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} else {
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if (*incx == 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.) {
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if (nounit) {
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x[j] /= a[j + j * a_dim1];
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}
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temp = x[j];
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i__2 = *n;
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for (i__ = j + 1; i__ <= i__2; ++i__) {
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x[i__] -= temp * a[i__ + j * a_dim1];
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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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jx = kx;
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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.) {
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if (nounit) {
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x[jx] /= a[j + j * a_dim1];
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}
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temp = x[jx];
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ix = jx;
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i__2 = *n;
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for (i__ = j + 1; i__ <= i__2; ++i__) {
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ix += *incx;
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x[ix] -= temp * a[i__ + j * a_dim1];
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/* L70: */
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}
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}
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jx += *incx;
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/* L80: */
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}
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}
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}
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} else {
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/* Form x := inv( A**T )*x. */
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if (igraphlsame_(uplo, "U")) {
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if (*incx == 1) {
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i__1 = *n;
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for (j = 1; j <= i__1; ++j) {
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temp = x[j];
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i__2 = j - 1;
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for (i__ = 1; i__ <= i__2; ++i__) {
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temp -= a[i__ + j * a_dim1] * x[i__];
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/* L90: */
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}
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if (nounit) {
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temp /= a[j + j * a_dim1];
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}
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x[j] = temp;
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/* L100: */
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}
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} else {
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jx = kx;
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i__1 = *n;
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for (j = 1; j <= i__1; ++j) {
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temp = x[jx];
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ix = kx;
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i__2 = j - 1;
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for (i__ = 1; i__ <= i__2; ++i__) {
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temp -= a[i__ + j * a_dim1] * x[ix];
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ix += *incx;
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/* L110: */
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}
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if (nounit) {
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temp /= a[j + j * a_dim1];
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}
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x[jx] = temp;
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jx += *incx;
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/* L120: */
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}
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}
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} else {
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if (*incx == 1) {
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for (j = *n; j >= 1; --j) {
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temp = x[j];
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i__1 = j + 1;
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for (i__ = *n; i__ >= i__1; --i__) {
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temp -= a[i__ + j * a_dim1] * x[i__];
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/* L130: */
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}
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if (nounit) {
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temp /= a[j + j * a_dim1];
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}
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x[j] = temp;
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/* L140: */
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}
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} else {
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kx += (*n - 1) * *incx;
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jx = kx;
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for (j = *n; j >= 1; --j) {
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temp = x[jx];
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ix = kx;
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i__1 = j + 1;
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for (i__ = *n; i__ >= i__1; --i__) {
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temp -= a[i__ + j * a_dim1] * x[ix];
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ix -= *incx;
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/* L150: */
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}
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if (nounit) {
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temp /= a[j + j * a_dim1];
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}
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x[jx] = temp;
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jx -= *incx;
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/* L160: */
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}
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}
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}
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}
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return 0;
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/* End of DTRSV */
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} /* igraphdtrsv_ */
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