c@427: /* dtrtri.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: static integer c_n1 = -1;
c@427: static integer c__2 = 2;
c@427: static doublereal c_b18 = 1.;
c@427: static doublereal c_b22 = -1.;
c@427: 
c@427: /* Subroutine */ int dtrtri_(char *uplo, char *diag, integer *n, doublereal *
c@427: 	a, integer *lda, integer *info)
c@427: {
c@427:     /* System generated locals */
c@427:     address a__1[2];
c@427:     integer a_dim1, a_offset, i__1, i__2[2], i__3, i__4, i__5;
c@427:     char ch__1[2];
c@427: 
c@427:     /* Builtin functions */
c@427:     /* Subroutine */ int s_cat(char *, char **, integer *, integer *, ftnlen);
c@427: 
c@427:     /* Local variables */
c@427:     integer j, jb, nb, nn;
c@427:     extern logical lsame_(char *, char *);
c@427:     extern /* Subroutine */ int dtrmm_(char *, char *, char *, char *, 
c@427: 	    integer *, integer *, doublereal *, doublereal *, integer *, 
c@427: 	    doublereal *, integer *), dtrsm_(
c@427: 	    char *, char *, char *, char *, integer *, integer *, doublereal *
c@427: , doublereal *, integer *, doublereal *, integer *);
c@427:     logical upper;
c@427:     extern /* Subroutine */ int dtrti2_(char *, char *, integer *, doublereal 
c@427: 	    *, integer *, integer *), xerbla_(char *, integer 
c@427: 	    *);
c@427:     extern integer ilaenv_(integer *, char *, char *, integer *, integer *, 
c@427: 	    integer *, 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: /*  DTRTRI computes the inverse of a real upper or lower triangular */
c@427: /*  matrix A. */
c@427: 
c@427: /*  This is the Level 3 BLAS version of the algorithm. */
c@427: 
c@427: /*  Arguments */
c@427: /*  ========= */
c@427: 
c@427: /*  UPLO    (input) CHARACTER*1 */
c@427: /*          = 'U':  A is upper triangular; */
c@427: /*          = 'L':  A is lower triangular. */
c@427: 
c@427: /*  DIAG    (input) CHARACTER*1 */
c@427: /*          = 'N':  A is non-unit triangular; */
c@427: /*          = 'U':  A is 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: /*          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 = -i, the i-th argument had an illegal value */
c@427: /*          > 0: if INFO = i, A(i,i) is exactly zero.  The triangular */
c@427: /*               matrix is singular and its inverse can not be computed. */
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_("DTRTRI", &i__1);
c@427: 	return 0;
c@427:     }
c@427: 
c@427: /*     Quick return if possible */
c@427: 
c@427:     if (*n == 0) {
c@427: 	return 0;
c@427:     }
c@427: 
c@427: /*     Check for singularity if non-unit. */
c@427: 
c@427:     if (nounit) {
c@427: 	i__1 = *n;
c@427: 	for (*info = 1; *info <= i__1; ++(*info)) {
c@427: 	    if (a[*info + *info * a_dim1] == 0.) {
c@427: 		return 0;
c@427: 	    }
c@427: /* L10: */
c@427: 	}
c@427: 	*info = 0;
c@427:     }
c@427: 
c@427: /*     Determine the block size for this environment. */
c@427: 
c@427: /* Writing concatenation */
c@427:     i__2[0] = 1, a__1[0] = uplo;
c@427:     i__2[1] = 1, a__1[1] = diag;
c@427:     s_cat(ch__1, a__1, i__2, &c__2, (ftnlen)2);
c@427:     nb = ilaenv_(&c__1, "DTRTRI", ch__1, n, &c_n1, &c_n1, &c_n1);
c@427:     if (nb <= 1 || nb >= *n) {
c@427: 
c@427: /*        Use unblocked code */
c@427: 
c@427: 	dtrti2_(uplo, diag, n, &a[a_offset], lda, info);
c@427:     } else {
c@427: 
c@427: /*        Use blocked code */
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: 	    i__3 = nb;
c@427: 	    for (j = 1; i__3 < 0 ? j >= i__1 : j <= i__1; j += i__3) {
c@427: /* Computing MIN */
c@427: 		i__4 = nb, i__5 = *n - j + 1;
c@427: 		jb = min(i__4,i__5);
c@427: 
c@427: /*              Compute rows 1:j-1 of current block column */
c@427: 
c@427: 		i__4 = j - 1;
c@427: 		dtrmm_("Left", "Upper", "No transpose", diag, &i__4, &jb, &
c@427: 			c_b18, &a[a_offset], lda, &a[j * a_dim1 + 1], lda);
c@427: 		i__4 = j - 1;
c@427: 		dtrsm_("Right", "Upper", "No transpose", diag, &i__4, &jb, &
c@427: 			c_b22, &a[j + j * a_dim1], lda, &a[j * a_dim1 + 1], 
c@427: 			lda);
c@427: 
c@427: /*              Compute inverse of current diagonal block */
c@427: 
c@427: 		dtrti2_("Upper", diag, &jb, &a[j + j * a_dim1], lda, info);
c@427: /* L20: */
c@427: 	    }
c@427: 	} else {
c@427: 
c@427: /*           Compute inverse of lower triangular matrix */
c@427: 
c@427: 	    nn = (*n - 1) / nb * nb + 1;
c@427: 	    i__3 = -nb;
c@427: 	    for (j = nn; i__3 < 0 ? j >= 1 : j <= 1; j += i__3) {
c@427: /* Computing MIN */
c@427: 		i__1 = nb, i__4 = *n - j + 1;
c@427: 		jb = min(i__1,i__4);
c@427: 		if (j + jb <= *n) {
c@427: 
c@427: /*                 Compute rows j+jb:n of current block column */
c@427: 
c@427: 		    i__1 = *n - j - jb + 1;
c@427: 		    dtrmm_("Left", "Lower", "No transpose", diag, &i__1, &jb, 
c@427: 			    &c_b18, &a[j + jb + (j + jb) * a_dim1], lda, &a[j 
c@427: 			    + jb + j * a_dim1], lda);
c@427: 		    i__1 = *n - j - jb + 1;
c@427: 		    dtrsm_("Right", "Lower", "No transpose", diag, &i__1, &jb, 
c@427: 			     &c_b22, &a[j + j * a_dim1], lda, &a[j + jb + j * 
c@427: 			    a_dim1], lda);
c@427: 		}
c@427: 
c@427: /*              Compute inverse of current diagonal block */
c@427: 
c@427: 		dtrti2_("Lower", diag, &jb, &a[j + j * a_dim1], lda, info);
c@427: /* L30: */
c@427: 	    }
c@427: 	}
c@427:     }
c@427: 
c@427:     return 0;
c@427: 
c@427: /*     End of DTRTRI */
c@427: 
c@427: } /* dtrtri_ */