/* fortran/dtrti2.f -- translated by f2c (version 20200916).
   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
*/

#ifdef __cplusplus
extern "C" {
#endif
#include "lmp_f2c.h"

/* Table of constant values */

static integer c__1 = 1;

/* > \brief \b DTRTI2 computes the inverse of a triangular matrix (unblocked algorithm). */

/*  =========== DOCUMENTATION =========== */

/* Online html documentation available at */
/*            http://www.netlib.org/lapack/explore-html/ */

/* > \htmlonly */
/* > Download DTRTI2 + dependencies */
/* > <a href="http://www.netlib.org/cgi-bin/netlibfiles.tgz?format=tgz&filename=/lapack/lapack_routine/dtrti2.
f"> */
/* > [TGZ]</a> */
/* > <a href="http://www.netlib.org/cgi-bin/netlibfiles.zip?format=zip&filename=/lapack/lapack_routine/dtrti2.
f"> */
/* > [ZIP]</a> */
/* > <a href="http://www.netlib.org/cgi-bin/netlibfiles.txt?format=txt&filename=/lapack/lapack_routine/dtrti2.
f"> */
/* > [TXT]</a> */
/* > \endhtmlonly */

/*  Definition: */
/*  =========== */

/*       SUBROUTINE DTRTI2( UPLO, DIAG, N, A, LDA, INFO ) */

/*       .. Scalar Arguments .. */
/*       CHARACTER          DIAG, UPLO */
/*       INTEGER            INFO, LDA, N */
/*       .. */
/*       .. Array Arguments .. */
/*       DOUBLE PRECISION   A( LDA, * ) */
/*       .. */


/* > \par Purpose: */
/*  ============= */
/* > */
/* > \verbatim */
/* > */
/* > DTRTI2 computes the inverse of a real upper or lower triangular */
/* > matrix. */
/* > */
/* > This is the Level 2 BLAS version of the algorithm. */
/* > \endverbatim */

/*  Arguments: */
/*  ========== */

/* > \param[in] UPLO */
/* > \verbatim */
/* >          UPLO is CHARACTER*1 */
/* >          Specifies whether the matrix A is upper or lower triangular. */
/* >          = 'U':  Upper triangular */
/* >          = 'L':  Lower triangular */
/* > \endverbatim */
/* > */
/* > \param[in] DIAG */
/* > \verbatim */
/* >          DIAG is CHARACTER*1 */
/* >          Specifies whether or not the matrix A is unit triangular. */
/* >          = 'N':  Non-unit triangular */
/* >          = 'U':  Unit triangular */
/* > \endverbatim */
/* > */
/* > \param[in] N */
/* > \verbatim */
/* >          N is INTEGER */
/* >          The order of the matrix A.  N >= 0. */
/* > \endverbatim */
/* > */
/* > \param[in,out] A */
/* > \verbatim */
/* >          A is 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. */
/* > \endverbatim */
/* > */
/* > \param[in] LDA */
/* > \verbatim */
/* >          LDA is INTEGER */
/* >          The leading dimension of the array A.  LDA >= max(1,N). */
/* > \endverbatim */
/* > */
/* > \param[out] INFO */
/* > \verbatim */
/* >          INFO is INTEGER */
/* >          = 0: successful exit */
/* >          < 0: if INFO = -k, the k-th argument had an illegal value */
/* > \endverbatim */

/*  Authors: */
/*  ======== */

/* > \author Univ. of Tennessee */
/* > \author Univ. of California Berkeley */
/* > \author Univ. of Colorado Denver */
/* > \author NAG Ltd. */

/* > \ingroup doubleOTHERcomputational */

/*  ===================================================================== */
/* Subroutine */ int dtrti2_(char *uplo, char *diag, integer *n, doublereal *
        a, integer *lda, integer *info, ftnlen uplo_len, ftnlen diag_len)
{
    /* 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 *, ftnlen, ftnlen);
    logical upper;
    extern /* Subroutine */ int dtrmv_(char *, char *, char *, integer *,
            doublereal *, integer *, doublereal *, integer *, ftnlen, ftnlen,
            ftnlen), xerbla_(char *, integer *, ftnlen);
    logical nounit;


/*  -- LAPACK computational routine -- */
/*  -- LAPACK is a software package provided by Univ. of Tennessee,    -- */
/*  -- Univ. of California Berkeley, Univ. of Colorado Denver and NAG Ltd..-- */

/*     .. Scalar Arguments .. */
/*     .. */
/*     .. Array Arguments .. */
/*     .. */

/*  ===================================================================== */

/*     .. 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, (char *)"U", (ftnlen)1, (ftnlen)1);
    nounit = lsame_(diag, (char *)"N", (ftnlen)1, (ftnlen)1);
    if (! upper && ! lsame_(uplo, (char *)"L", (ftnlen)1, (ftnlen)1)) {
        *info = -1;
    } else if (! nounit && ! lsame_(diag, (char *)"U", (ftnlen)1, (ftnlen)1)) {
        *info = -2;
    } else if (*n < 0) {
        *info = -3;
    } else if (*lda < max(1,*n)) {
        *info = -5;
    }
    if (*info != 0) {
        i__1 = -(*info);
        xerbla_((char *)"DTRTI2", &i__1, (ftnlen)6);
        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_((char *)"Upper", (char *)"No transpose", diag, &i__2, &a[a_offset], lda, &
                    a[j * a_dim1 + 1], &c__1, (ftnlen)5, (ftnlen)12, (ftnlen)
                    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_((char *)"Lower", (char *)"No transpose", diag, &i__1, &a[j + 1 + (j +
                        1) * a_dim1], lda, &a[j + 1 + j * a_dim1], &c__1, (
                        ftnlen)5, (ftnlen)12, (ftnlen)1);
                i__1 = *n - j;
                dscal_(&i__1, &ajj, &a[j + 1 + j * a_dim1], &c__1);
            }
/* L20: */
        }
    }

    return 0;

/*     End of DTRTI2 */

} /* dtrti2_ */

#ifdef __cplusplus
        }
#endif