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/* dtrtri.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;
static integer c_n1 = -1;
static integer c__2 = 2;
static doublereal c_b18 = 1.;
static doublereal c_b22 = -1.;
/* Subroutine */ int dtrtri_(char *uplo, char *diag, integer *n, doublereal *
a, integer *lda, integer *info)
{
/* System generated locals */
address a__1[2];
integer a_dim1, a_offset, i__1, i__2[2], i__3, i__4, i__5;
char ch__1[3];
ch__1[2] = 0;
/* Builtin functions */
/* Subroutine */ int s_cat(char *, char **, integer *, integer *, ftnlen);
/* Local variables */
integer j, jb, nb, nn;
extern logical lsame_(char *, char *);
extern /* Subroutine */ int dtrmm_(char *, char *, char *, char *,
integer *, integer *, doublereal *, doublereal *, integer *,
doublereal *, integer *), dtrsm_(
char *, char *, char *, char *, integer *, integer *, doublereal *
, doublereal *, integer *, doublereal *, integer *);
logical upper;
extern /* Subroutine */ int dtrti2_(char *, char *, integer *, doublereal
*, integer *, integer *), xerbla_(char *, integer
*);
extern integer ilaenv_(integer *, char *, char *, integer *, integer *,
integer *, 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 */
/* ======= */
/* DTRTRI computes the inverse of a real upper or lower triangular */
/* matrix A. */
/* This is the Level 3 BLAS version of the algorithm. */
/* Arguments */
/* ========= */
/* UPLO (input) CHARACTER*1 */
/* = 'U': A is upper triangular; */
/* = 'L': A is lower triangular. */
/* DIAG (input) CHARACTER*1 */
/* = 'N': A is non-unit triangular; */
/* = 'U': A is 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 = -i, the i-th argument had an illegal value */
/* > 0: if INFO = i, A(i,i) is exactly zero. The triangular */
/* matrix is singular and its inverse can not be computed. */
/* ===================================================================== */
/* .. 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_("DTRTRI", &i__1);
return 0;
}
/* Quick return if possible */
if (*n == 0) {
return 0;
}
/* Check for singularity if non-unit. */
if (nounit) {
i__1 = *n;
for (*info = 1; *info <= i__1; ++(*info)) {
if (a[*info + *info * a_dim1] == 0.) {
return 0;
}
/* L10: */
}
*info = 0;
}
/* Determine the block size for this environment. */
/* Writing concatenation */
i__2[0] = 1, a__1[0] = uplo;
i__2[1] = 1, a__1[1] = diag;
s_cat(ch__1, a__1, i__2, &c__2, (ftnlen)2);
nb = ilaenv_(&c__1, "DTRTRI", ch__1, n, &c_n1, &c_n1, &c_n1);
if (nb <= 1 || nb >= *n) {
/* Use unblocked code */
dtrti2_(uplo, diag, n, &a[a_offset], lda, info);
} else {
/* Use blocked code */
if (upper) {
/* Compute inverse of upper triangular matrix */
i__1 = *n;
i__3 = nb;
for (j = 1; i__3 < 0 ? j >= i__1 : j <= i__1; j += i__3) {
/* Computing MIN */
i__4 = nb, i__5 = *n - j + 1;
jb = min(i__4,i__5);
/* Compute rows 1:j-1 of current block column */
i__4 = j - 1;
dtrmm_("Left", "Upper", "No transpose", diag, &i__4, &jb, &
c_b18, &a[a_offset], lda, &a[j * a_dim1 + 1], lda);
i__4 = j - 1;
dtrsm_("Right", "Upper", "No transpose", diag, &i__4, &jb, &
c_b22, &a[j + j * a_dim1], lda, &a[j * a_dim1 + 1],
lda);
/* Compute inverse of current diagonal block */
dtrti2_("Upper", diag, &jb, &a[j + j * a_dim1], lda, info);
/* L20: */
}
} else {
/* Compute inverse of lower triangular matrix */
nn = (*n - 1) / nb * nb + 1;
i__3 = -nb;
for (j = nn; i__3 < 0 ? j >= 1 : j <= 1; j += i__3) {
/* Computing MIN */
i__1 = nb, i__4 = *n - j + 1;
jb = min(i__1,i__4);
if (j + jb <= *n) {
/* Compute rows j+jb:n of current block column */
i__1 = *n - j - jb + 1;
dtrmm_("Left", "Lower", "No transpose", diag, &i__1, &jb,
&c_b18, &a[j + jb + (j + jb) * a_dim1], lda, &a[j
+ jb + j * a_dim1], lda);
i__1 = *n - j - jb + 1;
dtrsm_("Right", "Lower", "No transpose", diag, &i__1, &jb,
&c_b22, &a[j + j * a_dim1], lda, &a[j + jb + j *
a_dim1], lda);
}
/* Compute inverse of current diagonal block */
dtrti2_("Lower", diag, &jb, &a[j + j * a_dim1], lda, info);
/* L30: */
}
}
}
return 0;
/* End of DTRTRI */
} /* dtrtri_ */
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