#include "f2c.h"

/* Subroutine */ int dpbtrs_(char *uplo, integer *n, integer *kd, integer *
	nrhs, doublereal *ab, integer *ldab, doublereal *b, integer *ldb,
	integer *info)
{
/*  -- LAPACK routine (version 2.0) --
       Univ. of Tennessee, Univ. of California Berkeley, NAG Ltd.,
       Courant Institute, Argonne National Lab, and Rice University
       September 30, 1994


    Purpose
    =======

    DPBTRS solves a system of linear equations A*X = B with a symmetric
    positive definite band matrix A using the Cholesky factorization
    A = U**T*U or A = L*L**T computed by DPBTRF.

    Arguments
    =========

    UPLO    (input) CHARACTER*1
            = 'U':  Upper triangular factor stored in AB;
            = 'L':  Lower triangular factor stored in AB.

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

    KD      (input) INTEGER
            The number of superdiagonals of the matrix A if UPLO = 'U',
            or the number of subdiagonals if UPLO = 'L'.  KD >= 0.

    NRHS    (input) INTEGER
            The number of right hand sides, i.e., the number of columns
            of the matrix B.  NRHS >= 0.

    AB      (input) DOUBLE PRECISION array, dimension (LDAB,N)
            The triangular factor U or L from the Cholesky factorization

            A = U**T*U or A = L*L**T of the band matrix A, stored in the

            first KD+1 rows of the array.  The j-th column of U or L is
            stored in the j-th column of the array AB as follows:
            if UPLO ='U', AB(kd+1+i-j,j) = U(i,j) for MAX(1,j-kd)<=i<=j;

            if UPLO ='L', AB(1+i-j,j)    = L(i,j) for j<=i<=MIN(n,j+kd).


    LDAB    (input) INTEGER
            The leading dimension of the array AB.  LDAB >= KD+1.

    B       (input/output) DOUBLE PRECISION array, dimension (LDB,NRHS)
            On entry, the right hand side matrix B.
            On exit, the solution matrix X.

    LDB     (input) INTEGER
            The leading dimension of the array B.  LDB >= MAX(1,N).

    INFO    (output) INTEGER
            = 0:  successful exit
            < 0:  if INFO = -i, the i-th argument had an illegal value

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



       Test the input parameters.


   Parameter adjustments
       Function Body */
    /* Table of constant values */
    static integer c__1 = 1;

    /* System generated locals */
    integer ab_dim1, ab_offset, b_dim1, b_offset, i__1;
    /* Local variables */
    static integer j;
    extern logical lsame_(char *, char *);
    extern /* Subroutine */ int dtbsv_(char *, char *, char *, integer *,
	    integer *, doublereal *, integer *, doublereal *, integer *);
    static logical upper;
    extern /* Subroutine */ int xerbla_(char *, integer *);




#define AB(I,J) ab[(I)-1 + ((J)-1)* ( *ldab)]
#define B(I,J) b[(I)-1 + ((J)-1)* ( *ldb)]

    *info = 0;
    upper = lsame_(uplo, "U");
    if (! upper && ! lsame_(uplo, "L")) {
	*info = -1;
    } else if (*n < 0) {
	*info = -2;
    } else if (*kd < 0) {
	*info = -3;
    } else if (*nrhs < 0) {
	*info = -4;
    } else if (*ldab < *kd + 1) {
	*info = -6;
    } else if (*ldb < MAX(1,*n)) {
	*info = -8;
    }
    if (*info != 0) {
	i__1 = -(*info);
	xerbla_("DPBTRS", &i__1);
	return 0;
    }

/*     Quick return if possible */

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

    if (upper) {

/*        Solve A*X = B where A = U'*U. */

	i__1 = *nrhs;
	for (j = 1; j <= *nrhs; ++j) {

/*           Solve U'*X = B, overwriting B with X. */

	    dtbsv_("Upper", "Transpose", "Non-unit", n, kd, &AB(1,1),
		    ldab, &B(1,j), &c__1);

/*           Solve U*X = B, overwriting B with X. */

	    dtbsv_("Upper", "No transpose", "Non-unit", n, kd, &AB(1,1),
		     ldab, &B(1,j), &c__1);
/* L10: */
	}
    } else {

/*        Solve A*X = B where A = L*L'. */

	i__1 = *nrhs;
	for (j = 1; j <= *nrhs; ++j) {

/*           Solve L*X = B, overwriting B with X. */

	    dtbsv_("Lower", "No transpose", "Non-unit", n, kd, &AB(1,1),
		     ldab, &B(1,j), &c__1);

/*           Solve L'*X = B, overwriting B with X. */

	    dtbsv_("Lower", "Transpose", "Non-unit", n, kd, &AB(1,1),
		    ldab, &B(1,j), &c__1);
/* L20: */
	}
    }

    return 0;

/*     End of DPBTRS */

} /* dpbtrs_ */

