Chris@202: /* dtrti2.f -- translated by f2c (version 20061008).
Chris@202:    You must link the resulting object file with libf2c:
Chris@202: 	on Microsoft Windows system, link with libf2c.lib;
Chris@202: 	on Linux or Unix systems, link with .../path/to/libf2c.a -lm
Chris@202: 	or, if you install libf2c.a in a standard place, with -lf2c -lm
Chris@202: 	-- in that order, at the end of the command line, as in
Chris@202: 		cc *.o -lf2c -lm
Chris@202: 	Source for libf2c is in /netlib/f2c/libf2c.zip, e.g.,
Chris@202: 
Chris@202: 		http://www.netlib.org/f2c/libf2c.zip
Chris@202: */
Chris@202: 
Chris@202: #include "f2c.h"
Chris@202: #include "blaswrap.h"
Chris@202: 
Chris@202: /* Table of constant values */
Chris@202: 
Chris@202: static integer c__1 = 1;
Chris@202: 
Chris@202: /* Subroutine */ int dtrti2_(char *uplo, char *diag, integer *n, doublereal *
Chris@202: 	a, integer *lda, integer *info)
Chris@202: {
Chris@202:     /* System generated locals */
Chris@202:     integer a_dim1, a_offset, i__1, i__2;
Chris@202: 
Chris@202:     /* Local variables */
Chris@202:     integer j;
Chris@202:     doublereal ajj;
Chris@202:     extern /* Subroutine */ int dscal_(integer *, doublereal *, doublereal *, 
Chris@202: 	    integer *);
Chris@202:     extern logical lsame_(char *, char *);
Chris@202:     logical upper;
Chris@202:     extern /* Subroutine */ int dtrmv_(char *, char *, char *, integer *, 
Chris@202: 	    doublereal *, integer *, doublereal *, integer *), xerbla_(char *, integer *);
Chris@202:     logical nounit;
Chris@202: 
Chris@202: 
Chris@202: /*  -- LAPACK routine (version 3.2) -- */
Chris@202: /*     Univ. of Tennessee, Univ. of California Berkeley and NAG Ltd.. */
Chris@202: /*     November 2006 */
Chris@202: 
Chris@202: /*     .. Scalar Arguments .. */
Chris@202: /*     .. */
Chris@202: /*     .. Array Arguments .. */
Chris@202: /*     .. */
Chris@202: 
Chris@202: /*  Purpose */
Chris@202: /*  ======= */
Chris@202: 
Chris@202: /*  DTRTI2 computes the inverse of a real upper or lower triangular */
Chris@202: /*  matrix. */
Chris@202: 
Chris@202: /*  This is the Level 2 BLAS version of the algorithm. */
Chris@202: 
Chris@202: /*  Arguments */
Chris@202: /*  ========= */
Chris@202: 
Chris@202: /*  UPLO    (input) CHARACTER*1 */
Chris@202: /*          Specifies whether the matrix A is upper or lower triangular. */
Chris@202: /*          = 'U':  Upper triangular */
Chris@202: /*          = 'L':  Lower triangular */
Chris@202: 
Chris@202: /*  DIAG    (input) CHARACTER*1 */
Chris@202: /*          Specifies whether or not the matrix A is unit triangular. */
Chris@202: /*          = 'N':  Non-unit triangular */
Chris@202: /*          = 'U':  Unit triangular */
Chris@202: 
Chris@202: /*  N       (input) INTEGER */
Chris@202: /*          The order of the matrix A.  N >= 0. */
Chris@202: 
Chris@202: /*  A       (input/output) DOUBLE PRECISION array, dimension (LDA,N) */
Chris@202: /*          On entry, the triangular matrix A.  If UPLO = 'U', the */
Chris@202: /*          leading n by n upper triangular part of the array A contains */
Chris@202: /*          the upper triangular matrix, and the strictly lower */
Chris@202: /*          triangular part of A is not referenced.  If UPLO = 'L', the */
Chris@202: /*          leading n by n lower triangular part of the array A contains */
Chris@202: /*          the lower triangular matrix, and the strictly upper */
Chris@202: /*          triangular part of A is not referenced.  If DIAG = 'U', the */
Chris@202: /*          diagonal elements of A are also not referenced and are */
Chris@202: /*          assumed to be 1. */
Chris@202: 
Chris@202: /*          On exit, the (triangular) inverse of the original matrix, in */
Chris@202: /*          the same storage format. */
Chris@202: 
Chris@202: /*  LDA     (input) INTEGER */
Chris@202: /*          The leading dimension of the array A.  LDA >= max(1,N). */
Chris@202: 
Chris@202: /*  INFO    (output) INTEGER */
Chris@202: /*          = 0: successful exit */
Chris@202: /*          < 0: if INFO = -k, the k-th argument had an illegal value */
Chris@202: 
Chris@202: /*  ===================================================================== */
Chris@202: 
Chris@202: /*     .. Parameters .. */
Chris@202: /*     .. */
Chris@202: /*     .. Local Scalars .. */
Chris@202: /*     .. */
Chris@202: /*     .. External Functions .. */
Chris@202: /*     .. */
Chris@202: /*     .. External Subroutines .. */
Chris@202: /*     .. */
Chris@202: /*     .. Intrinsic Functions .. */
Chris@202: /*     .. */
Chris@202: /*     .. Executable Statements .. */
Chris@202: 
Chris@202: /*     Test the input parameters. */
Chris@202: 
Chris@202:     /* Parameter adjustments */
Chris@202:     a_dim1 = *lda;
Chris@202:     a_offset = 1 + a_dim1;
Chris@202:     a -= a_offset;
Chris@202: 
Chris@202:     /* Function Body */
Chris@202:     *info = 0;
Chris@202:     upper = lsame_(uplo, "U");
Chris@202:     nounit = lsame_(diag, "N");
Chris@202:     if (! upper && ! lsame_(uplo, "L")) {
Chris@202: 	*info = -1;
Chris@202:     } else if (! nounit && ! lsame_(diag, "U")) {
Chris@202: 	*info = -2;
Chris@202:     } else if (*n < 0) {
Chris@202: 	*info = -3;
Chris@202:     } else if (*lda < max(1,*n)) {
Chris@202: 	*info = -5;
Chris@202:     }
Chris@202:     if (*info != 0) {
Chris@202: 	i__1 = -(*info);
Chris@202: 	xerbla_("DTRTI2", &i__1);
Chris@202: 	return 0;
Chris@202:     }
Chris@202: 
Chris@202:     if (upper) {
Chris@202: 
Chris@202: /*        Compute inverse of upper triangular matrix. */
Chris@202: 
Chris@202: 	i__1 = *n;
Chris@202: 	for (j = 1; j <= i__1; ++j) {
Chris@202: 	    if (nounit) {
Chris@202: 		a[j + j * a_dim1] = 1. / a[j + j * a_dim1];
Chris@202: 		ajj = -a[j + j * a_dim1];
Chris@202: 	    } else {
Chris@202: 		ajj = -1.;
Chris@202: 	    }
Chris@202: 
Chris@202: /*           Compute elements 1:j-1 of j-th column. */
Chris@202: 
Chris@202: 	    i__2 = j - 1;
Chris@202: 	    dtrmv_("Upper", "No transpose", diag, &i__2, &a[a_offset], lda, &
Chris@202: 		    a[j * a_dim1 + 1], &c__1);
Chris@202: 	    i__2 = j - 1;
Chris@202: 	    dscal_(&i__2, &ajj, &a[j * a_dim1 + 1], &c__1);
Chris@202: /* L10: */
Chris@202: 	}
Chris@202:     } else {
Chris@202: 
Chris@202: /*        Compute inverse of lower triangular matrix. */
Chris@202: 
Chris@202: 	for (j = *n; j >= 1; --j) {
Chris@202: 	    if (nounit) {
Chris@202: 		a[j + j * a_dim1] = 1. / a[j + j * a_dim1];
Chris@202: 		ajj = -a[j + j * a_dim1];
Chris@202: 	    } else {
Chris@202: 		ajj = -1.;
Chris@202: 	    }
Chris@202: 	    if (j < *n) {
Chris@202: 
Chris@202: /*              Compute elements j+1:n of j-th column. */
Chris@202: 
Chris@202: 		i__1 = *n - j;
Chris@202: 		dtrmv_("Lower", "No transpose", diag, &i__1, &a[j + 1 + (j + 
Chris@202: 			1) * a_dim1], lda, &a[j + 1 + j * a_dim1], &c__1);
Chris@202: 		i__1 = *n - j;
Chris@202: 		dscal_(&i__1, &ajj, &a[j + 1 + j * a_dim1], &c__1);
Chris@202: 	    }
Chris@202: /* L20: */
Chris@202: 	}
Chris@202:     }
Chris@202: 
Chris@202:     return 0;
Chris@202: 
Chris@202: /*     End of DTRTI2 */
Chris@202: 
Chris@202: } /* dtrti2_ */