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/* dtrti2.f -- translated by f2c (version 20061008).
You must link the resulting object file with libf2c:
on Microsoft Windows system, link with libf2c.lib;
on Linux or Unix systems, link with .../path/to/libf2c.a -lm
or, if you install libf2c.a in a standard place, with -lf2c -lm
-- in that order, at the end of the command line, as in
cc *.o -lf2c -lm
Source for libf2c is in /netlib/f2c/libf2c.zip, e.g.,
http://www.netlib.org/f2c/libf2c.zip
*/
#include "f2c.h"
#include "blaswrap.h"
/* Table of constant values */
static integer c__1 = 1;
/* Subroutine */ int dtrti2_(char *uplo, char *diag, integer *n, doublereal *
a, integer *lda, integer *info)
{
/* System generated locals */
integer a_dim1, a_offset, i__1, i__2;
/* Local variables */
integer j;
doublereal ajj;
extern /* Subroutine */ int dscal_(integer *, doublereal *, doublereal *,
integer *);
extern logical lsame_(char *, char *);
logical upper;
extern /* Subroutine */ int dtrmv_(char *, char *, char *, integer *,
doublereal *, integer *, doublereal *, integer *), xerbla_(char *, integer *);
logical nounit;
/* -- LAPACK routine (version 3.2) -- */
/* Univ. of Tennessee, Univ. of California Berkeley and NAG Ltd.. */
/* November 2006 */
/* .. Scalar Arguments .. */
/* .. */
/* .. Array Arguments .. */
/* .. */
/* Purpose */
/* ======= */
/* DTRTI2 computes the inverse of a real upper or lower triangular */
/* matrix. */
/* This is the Level 2 BLAS version of the algorithm. */
/* Arguments */
/* ========= */
/* UPLO (input) CHARACTER*1 */
/* Specifies whether the matrix A is upper or lower triangular. */
/* = 'U': Upper triangular */
/* = 'L': Lower triangular */
/* DIAG (input) CHARACTER*1 */
/* Specifies whether or not the matrix A is unit triangular. */
/* = 'N': Non-unit triangular */
/* = 'U': Unit triangular */
/* N (input) INTEGER */
/* The order of the matrix A. N >= 0. */
/* A (input/output) DOUBLE PRECISION array, dimension (LDA,N) */
/* On entry, the triangular matrix A. If UPLO = 'U', the */
/* leading n by n upper triangular part of the array A contains */
/* the upper triangular matrix, and the strictly lower */
/* triangular part of A is not referenced. If UPLO = 'L', the */
/* leading n by n lower triangular part of the array A contains */
/* the lower triangular matrix, and the strictly upper */
/* triangular part of A is not referenced. If DIAG = 'U', the */
/* diagonal elements of A are also not referenced and are */
/* assumed to be 1. */
/* On exit, the (triangular) inverse of the original matrix, in */
/* the same storage format. */
/* LDA (input) INTEGER */
/* The leading dimension of the array A. LDA >= max(1,N). */
/* INFO (output) INTEGER */
/* = 0: successful exit */
/* < 0: if INFO = -k, the k-th argument had an illegal value */
/* ===================================================================== */
/* .. Parameters .. */
/* .. */
/* .. Local Scalars .. */
/* .. */
/* .. External Functions .. */
/* .. */
/* .. External Subroutines .. */
/* .. */
/* .. Intrinsic Functions .. */
/* .. */
/* .. Executable Statements .. */
/* Test the input parameters. */
/* Parameter adjustments */
a_dim1 = *lda;
a_offset = 1 + a_dim1;
a -= a_offset;
/* Function Body */
*info = 0;
upper = lsame_(uplo, "U");
nounit = lsame_(diag, "N");
if (! upper && ! lsame_(uplo, "L")) {
*info = -1;
} else if (! nounit && ! lsame_(diag, "U")) {
*info = -2;
} else if (*n < 0) {
*info = -3;
} else if (*lda < max(1,*n)) {
*info = -5;
}
if (*info != 0) {
i__1 = -(*info);
xerbla_("DTRTI2", &i__1);
return 0;
}
if (upper) {
/* Compute inverse of upper triangular matrix. */
i__1 = *n;
for (j = 1; j <= i__1; ++j) {
if (nounit) {
a[j + j * a_dim1] = 1. / a[j + j * a_dim1];
ajj = -a[j + j * a_dim1];
} else {
ajj = -1.;
}
/* Compute elements 1:j-1 of j-th column. */
i__2 = j - 1;
dtrmv_("Upper", "No transpose", diag, &i__2, &a[a_offset], lda, &
a[j * a_dim1 + 1], &c__1);
i__2 = j - 1;
dscal_(&i__2, &ajj, &a[j * a_dim1 + 1], &c__1);
/* L10: */
}
} else {
/* Compute inverse of lower triangular matrix. */
for (j = *n; j >= 1; --j) {
if (nounit) {
a[j + j * a_dim1] = 1. / a[j + j * a_dim1];
ajj = -a[j + j * a_dim1];
} else {
ajj = -1.;
}
if (j < *n) {
/* Compute elements j+1:n of j-th column. */
i__1 = *n - j;
dtrmv_("Lower", "No transpose", diag, &i__1, &a[j + 1 + (j +
1) * a_dim1], lda, &a[j + 1 + j * a_dim1], &c__1);
i__1 = *n - j;
dscal_(&i__1, &ajj, &a[j + 1 + j * a_dim1], &c__1);
}
/* L20: */
}
}
return 0;
/* End of DTRTI2 */
} /* dtrti2_ */
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