c@427: /* dtrti2.f -- translated by f2c (version 20061008).
c@427:    You must link the resulting object file with libf2c:
c@427: 	on Microsoft Windows system, link with libf2c.lib;
c@427: 	on Linux or Unix systems, link with .../path/to/libf2c.a -lm
c@427: 	or, if you install libf2c.a in a standard place, with -lf2c -lm
c@427: 	-- in that order, at the end of the command line, as in
c@427: 		cc *.o -lf2c -lm
c@427: 	Source for libf2c is in /netlib/f2c/libf2c.zip, e.g.,
c@427: 
c@427: 		http://www.netlib.org/f2c/libf2c.zip
c@427: */
c@427: 
c@427: #include "f2c.h"
c@427: #include "blaswrap.h"
c@427: 
c@427: /* Table of constant values */
c@427: 
c@427: static integer c__1 = 1;
c@427: 
c@427: /* Subroutine */ int dtrti2_(char *uplo, char *diag, integer *n, doublereal *
c@427: 	a, integer *lda, integer *info)
c@427: {
c@427:     /* System generated locals */
c@427:     integer a_dim1, a_offset, i__1, i__2;
c@427: 
c@427:     /* Local variables */
c@427:     integer j;
c@427:     doublereal ajj;
c@427:     extern /* Subroutine */ int dscal_(integer *, doublereal *, doublereal *, 
c@427: 	    integer *);
c@427:     extern logical lsame_(char *, char *);
c@427:     logical upper;
c@427:     extern /* Subroutine */ int dtrmv_(char *, char *, char *, integer *, 
c@427: 	    doublereal *, integer *, doublereal *, integer *), xerbla_(char *, integer *);
c@427:     logical nounit;
c@427: 
c@427: 
c@427: /*  -- LAPACK routine (version 3.2) -- */
c@427: /*     Univ. of Tennessee, Univ. of California Berkeley and NAG Ltd.. */
c@427: /*     November 2006 */
c@427: 
c@427: /*     .. Scalar Arguments .. */
c@427: /*     .. */
c@427: /*     .. Array Arguments .. */
c@427: /*     .. */
c@427: 
c@427: /*  Purpose */
c@427: /*  ======= */
c@427: 
c@427: /*  DTRTI2 computes the inverse of a real upper or lower triangular */
c@427: /*  matrix. */
c@427: 
c@427: /*  This is the Level 2 BLAS version of the algorithm. */
c@427: 
c@427: /*  Arguments */
c@427: /*  ========= */
c@427: 
c@427: /*  UPLO    (input) CHARACTER*1 */
c@427: /*          Specifies whether the matrix A is upper or lower triangular. */
c@427: /*          = 'U':  Upper triangular */
c@427: /*          = 'L':  Lower triangular */
c@427: 
c@427: /*  DIAG    (input) CHARACTER*1 */
c@427: /*          Specifies whether or not the matrix A is unit triangular. */
c@427: /*          = 'N':  Non-unit triangular */
c@427: /*          = 'U':  Unit triangular */
c@427: 
c@427: /*  N       (input) INTEGER */
c@427: /*          The order of the matrix A.  N >= 0. */
c@427: 
c@427: /*  A       (input/output) DOUBLE PRECISION array, dimension (LDA,N) */
c@427: /*          On entry, the triangular matrix A.  If UPLO = 'U', the */
c@427: /*          leading n by n upper triangular part of the array A contains */
c@427: /*          the upper triangular matrix, and the strictly lower */
c@427: /*          triangular part of A is not referenced.  If UPLO = 'L', the */
c@427: /*          leading n by n lower triangular part of the array A contains */
c@427: /*          the lower triangular matrix, and the strictly upper */
c@427: /*          triangular part of A is not referenced.  If DIAG = 'U', the */
c@427: /*          diagonal elements of A are also not referenced and are */
c@427: /*          assumed to be 1. */
c@427: 
c@427: /*          On exit, the (triangular) inverse of the original matrix, in */
c@427: /*          the same storage format. */
c@427: 
c@427: /*  LDA     (input) INTEGER */
c@427: /*          The leading dimension of the array A.  LDA >= max(1,N). */
c@427: 
c@427: /*  INFO    (output) INTEGER */
c@427: /*          = 0: successful exit */
c@427: /*          < 0: if INFO = -k, the k-th argument had an illegal value */
c@427: 
c@427: /*  ===================================================================== */
c@427: 
c@427: /*     .. Parameters .. */
c@427: /*     .. */
c@427: /*     .. Local Scalars .. */
c@427: /*     .. */
c@427: /*     .. External Functions .. */
c@427: /*     .. */
c@427: /*     .. External Subroutines .. */
c@427: /*     .. */
c@427: /*     .. Intrinsic Functions .. */
c@427: /*     .. */
c@427: /*     .. Executable Statements .. */
c@427: 
c@427: /*     Test the input parameters. */
c@427: 
c@427:     /* Parameter adjustments */
c@427:     a_dim1 = *lda;
c@427:     a_offset = 1 + a_dim1;
c@427:     a -= a_offset;
c@427: 
c@427:     /* Function Body */
c@427:     *info = 0;
c@427:     upper = lsame_(uplo, "U");
c@427:     nounit = lsame_(diag, "N");
c@427:     if (! upper && ! lsame_(uplo, "L")) {
c@427: 	*info = -1;
c@427:     } else if (! nounit && ! lsame_(diag, "U")) {
c@427: 	*info = -2;
c@427:     } else if (*n < 0) {
c@427: 	*info = -3;
c@427:     } else if (*lda < max(1,*n)) {
c@427: 	*info = -5;
c@427:     }
c@427:     if (*info != 0) {
c@427: 	i__1 = -(*info);
c@427: 	xerbla_("DTRTI2", &i__1);
c@427: 	return 0;
c@427:     }
c@427: 
c@427:     if (upper) {
c@427: 
c@427: /*        Compute inverse of upper triangular matrix. */
c@427: 
c@427: 	i__1 = *n;
c@427: 	for (j = 1; j <= i__1; ++j) {
c@427: 	    if (nounit) {
c@427: 		a[j + j * a_dim1] = 1. / a[j + j * a_dim1];
c@427: 		ajj = -a[j + j * a_dim1];
c@427: 	    } else {
c@427: 		ajj = -1.;
c@427: 	    }
c@427: 
c@427: /*           Compute elements 1:j-1 of j-th column. */
c@427: 
c@427: 	    i__2 = j - 1;
c@427: 	    dtrmv_("Upper", "No transpose", diag, &i__2, &a[a_offset], lda, &
c@427: 		    a[j * a_dim1 + 1], &c__1);
c@427: 	    i__2 = j - 1;
c@427: 	    dscal_(&i__2, &ajj, &a[j * a_dim1 + 1], &c__1);
c@427: /* L10: */
c@427: 	}
c@427:     } else {
c@427: 
c@427: /*        Compute inverse of lower triangular matrix. */
c@427: 
c@427: 	for (j = *n; j >= 1; --j) {
c@427: 	    if (nounit) {
c@427: 		a[j + j * a_dim1] = 1. / a[j + j * a_dim1];
c@427: 		ajj = -a[j + j * a_dim1];
c@427: 	    } else {
c@427: 		ajj = -1.;
c@427: 	    }
c@427: 	    if (j < *n) {
c@427: 
c@427: /*              Compute elements j+1:n of j-th column. */
c@427: 
c@427: 		i__1 = *n - j;
c@427: 		dtrmv_("Lower", "No transpose", diag, &i__1, &a[j + 1 + (j + 
c@427: 			1) * a_dim1], lda, &a[j + 1 + j * a_dim1], &c__1);
c@427: 		i__1 = *n - j;
c@427: 		dscal_(&i__1, &ajj, &a[j + 1 + j * a_dim1], &c__1);
c@427: 	    }
c@427: /* L20: */
c@427: 	}
c@427:     }
c@427: 
c@427:     return 0;
c@427: 
c@427: /*     End of DTRTI2 */
c@427: 
c@427: } /* dtrti2_ */