/* Copyright (c) 1992-2008 The University of Tennessee.  All rights reserved.
 * See file COPYING in this directory for details. */

#ifdef __cplusplus
extern "C" {
#endif

#include "f2c.h"
#include "hypre_lapack.h"

/* Subroutine */ integer dgetri_(integer *n, doublereal *a, integer *lda, integer
	*ipiv, doublereal *work, integer *lwork, integer *info)
{
/*  -- LAPACK routine (version 3.0) --
       Univ. of Tennessee, Univ. of California Berkeley, NAG Ltd.,
       Courant Institute, Argonne National Lab, and Rice University
       June 30, 1999


    Purpose
    =======

    DGETRI computes the inverse of a matrix using the LU factorization
    computed by DGETRF.

    This method inverts U and then computes inv(A) by solving the system
    inv(A)*L = inv(U) for inv(A).

    Arguments
    =========

    N       (input) INTEGER
            The order of the matrix A.  N >= 0.

    A       (input/output) DOUBLE PRECISION array, dimension (LDA,N)
            On entry, the factors L and U from the factorization
            A = P*L*U as computed by DGETRF.
            On exit, if INFO = 0, the inverse of the original matrix A.

    LDA     (input) INTEGER
            The leading dimension of the array A.  LDA >= max(1,N).

    IPIV    (input) INTEGER array, dimension (N)
            The pivot indices from DGETRF; for 1<=i<=N, row i of the
            matrix was interchanged with row IPIV(i).

    WORK    (workspace/output) DOUBLE PRECISION array, dimension (LWORK)
            On exit, if INFO=0, then WORK(1) returns the optimal LWORK.

    LWORK   (input) INTEGER
            The dimension of the array WORK.  LWORK >= max(1,N).
            For optimal performance LWORK >= N*NB, where NB is
            the optimal blocksize returned by ILAENV.

            If LWORK = -1, then a workspace query is assumed; the routine
            only calculates the optimal size of the WORK array, returns
            this value as the first entry of the WORK array, and no error
            message related to LWORK is issued by XERBLA.

    INFO    (output) INTEGER
            = 0:  successful exit
            < 0:  if INFO = -i, the i-th argument had an illegal value
            > 0:  if INFO = i, U(i,i) is exactly zero; the matrix is
                  singular and its inverse could not be computed.

    =====================================================================


       Test the input parameters.

       Parameter adjustments */
    /* Table of constant values */
    integer c__1 = 1;
    integer c_n1 = -1;
    integer c__2 = 2;
    doublereal c_b20 = -1.;
    doublereal c_b22 = 1.;

    /* System generated locals */
    integer a_dim1, a_offset, i__1, i__2, i__3;
    /* Local variables */
    integer i__, j;
    extern /* Subroutine */ integer dgemm_(const char *, const char *, integer *, integer *,
	    integer *, doublereal *, doublereal *, integer *, doublereal *,
	    integer *, doublereal *, doublereal *, integer *),
	     dgemv_(const char *, integer *, integer *, doublereal *, doublereal *,
	    integer *, doublereal *, integer *, doublereal *, doublereal *,
	    integer *);
    integer nbmin;
    extern /* Subroutine */ integer dswap_(integer *, doublereal *, integer *,
	    doublereal *, integer *), dtrsm_(const char *, const char *, const char *, const char *,
	    integer *, integer *, doublereal *, doublereal *, integer *,
	    doublereal *, integer *);
    integer jb, nb, jj, jp, nn;
    extern /* Subroutine */ integer xerbla_(const char *, integer *);
    extern integer ilaenv_(integer *, const char *, const char *, integer *, integer *,
	    integer *, integer *, ftnlen, ftnlen);
    integer ldwork;
    extern /* Subroutine */ integer dtrtri_(const char *, const char *, integer *, doublereal
	    *, integer *, integer *);
    integer lwkopt;
    logical lquery;
    integer iws;
#define a_ref(a_1,a_2) a[(a_2)*a_dim1 + a_1]


    a_dim1 = *lda;
    a_offset = 1 + a_dim1 * 1;
    a -= a_offset;
    --ipiv;
    --work;

    /* Function Body */
    *info = 0;
    nb = ilaenv_(&c__1, "DGETRI", " ", n, &c_n1, &c_n1, &c_n1, (ftnlen)6, (
	    ftnlen)1);
    lwkopt = *n * nb;
    work[1] = (doublereal) lwkopt;
    lquery = *lwork == -1;
    if (*n < 0) {
	*info = -1;
    } else if (*lda < max(1,*n)) {
	*info = -3;
    } else if (*lwork < max(1,*n) && ! lquery) {
	*info = -6;
    }
    if (*info != 0) {
	i__1 = -(*info);
	xerbla_("DGETRI", &i__1);
	return 0;
    } else if (lquery) {
	return 0;
    }

/*     Quick return if possible */

    if (*n == 0) {
	return 0;
    }

/*     Form inv(U).  If INFO > 0 from DTRTRI, then U is singular,
       and the inverse is not computed. */

    dtrtri_("Upper", "Non-unit", n, &a[a_offset], lda, info);
    if (*info > 0) {
	return 0;
    }

    nbmin = 2;
    ldwork = *n;
    if (nb > 1 && nb < *n) {
/* Computing MAX */
	i__1 = ldwork * nb;
	iws = max(i__1,1);
	if (*lwork < iws) {
	    nb = *lwork / ldwork;
/* Computing MAX */
	    i__1 = 2, i__2 = ilaenv_(&c__2, "DGETRI", " ", n, &c_n1, &c_n1, &
		    c_n1, (ftnlen)6, (ftnlen)1);
	    nbmin = max(i__1,i__2);
	}
    } else {
	iws = *n;
    }

/*     Solve the equation inv(A)*L = inv(U) for inv(A). */

    if (nb < nbmin || nb >= *n) {

/*        Use unblocked code. */

	for (j = *n; j >= 1; --j) {

/*           Copy current column of L to WORK and replace with zeros. */

	    i__1 = *n;
	    for (i__ = j + 1; i__ <= i__1; ++i__) {
		work[i__] = a_ref(i__, j);
		a_ref(i__, j) = 0.;
/* L10: */
	    }

/*           Compute current column of inv(A). */

	    if (j < *n) {
		i__1 = *n - j;
		dgemv_("No transpose", n, &i__1, &c_b20, &a_ref(1, j + 1),
			lda, &work[j + 1], &c__1, &c_b22, &a_ref(1, j), &c__1);
	    }
/* L20: */
	}
    } else {

/*        Use blocked code. */

	nn = (*n - 1) / nb * nb + 1;
	i__1 = -nb;
	for (j = nn; i__1 < 0 ? j >= 1 : j <= 1; j += i__1) {
/* Computing MIN */
	    i__2 = nb, i__3 = *n - j + 1;
	    jb = min(i__2,i__3);

/*           Copy current block column of L to WORK and replace with
             zeros. */

	    i__2 = j + jb - 1;
	    for (jj = j; jj <= i__2; ++jj) {
		i__3 = *n;
		for (i__ = jj + 1; i__ <= i__3; ++i__) {
		    work[i__ + (jj - j) * ldwork] = a_ref(i__, jj);
		    a_ref(i__, jj) = 0.;
/* L30: */
		}
/* L40: */
	    }

/*           Compute current block column of inv(A). */

	    if (j + jb <= *n) {
		i__2 = *n - j - jb + 1;
		dgemm_("No transpose", "No transpose", n, &jb, &i__2, &c_b20,
			&a_ref(1, j + jb), lda, &work[j + jb], &ldwork, &
			c_b22, &a_ref(1, j), lda);
	    }
	    dtrsm_("Right", "Lower", "No transpose", "Unit", n, &jb, &c_b22, &
		    work[j], &ldwork, &a_ref(1, j), lda);
/* L50: */
	}
    }

/*     Apply column interchanges. */

    for (j = *n - 1; j >= 1; --j) {
	jp = ipiv[j];
	if (jp != j) {
	    dswap_(n, &a_ref(1, j), &c__1, &a_ref(1, jp), &c__1);
	}
/* L60: */
    }

    work[1] = (doublereal) iws;
    return 0;

/*     End of DGETRI */

} /* dgetri_ */

#undef a_ref

#ifdef __cplusplus
}
#endif
