#include "clapack.h"
#include "f2cP.h"

/* Table of constant values */

static double c_b7 = -1.;
static integer c__1 = 1;
static double c_b23 = 1.;

/* Subroutine */ int dgbtrs_(const char *trans, integer *n, integer *kl, integer *
	ku, integer *nrhs, double *ab, integer *ldab, integer *ipiv, 
	double *b, integer *ldb, integer *info)
{
    /* System generated locals */
    integer ab_dim1, ab_offset, b_dim1, b_offset, i__1, i__2, i__3;

    /* Local variables */
    integer i__, j, l, kd, lm;
    bool lnoti;
    bool notran;


/*  -- LAPACK routine (version 3.1) -- */
/*     Univ. of Tennessee, Univ. of California Berkeley and NAG Ltd.. */
/*     November 2006 */

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

/*  Purpose */
/*  ======= */

/*  DGBTRS solves a system of linear equations */
/*     A * X = B  or  A' * X = B */
/*  with a general band matrix A using the LU factorization computed */
/*  by DGBTRF. */

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

/*  TRANS   (input) CHARACTER*1 */
/*          Specifies the form of the system of equations. */
/*          = 'N':  A * X = B  (No transpose) */
/*          = 'T':  A'* X = B  (Transpose) */
/*          = 'C':  A'* X = B  (Conjugate transpose = Transpose) */

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

/*  KL      (input) INTEGER */
/*          The number of subdiagonals within the band of A.  KL >= 0. */

/*  KU      (input) INTEGER */
/*          The number of superdiagonals within the band of A.  KU >= 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) */
/*          Details of the LU factorization of the band matrix A, as */
/*          computed by DGBTRF.  U is stored as an upper triangular band */
/*          matrix with KL+KU superdiagonals in rows 1 to KL+KU+1, and */
/*          the multipliers used during the factorization are stored in */
/*          rows KL+KU+2 to 2*KL+KU+1. */

/*  LDAB    (input) INTEGER */
/*          The leading dimension of the array AB.  LDAB >= 2*KL+KU+1. */

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

/*  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 */

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

/*     .. Parameters .. */
/*     .. */
/*     .. Local Scalars .. */
/*     .. */
/*     .. External Functions .. */
/*     .. */
/*     .. External Subroutines .. */
/*     .. */
/*     .. Intrinsic Functions .. */
/*     .. */
/*     .. Executable Statements .. */

/*     Test the input parameters. */

    /* Parameter adjustments */
    ab_dim1 = *ldab;
    ab_offset = 1 + ab_dim1;
    ab -= ab_offset;
    --ipiv;
    b_dim1 = *ldb;
    b_offset = 1 + b_dim1;
    b -= b_offset;

    /* Function Body */
    *info = 0;
    notran = lsame_(trans, "N");
    if (! notran && ! lsame_(trans, "T") && ! lsame_(
	    trans, "C")) {
	*info = -1;
    } else if (*n < 0) {
	*info = -2;
    } else if (*kl < 0) {
	*info = -3;
    } else if (*ku < 0) {
	*info = -4;
    } else if (*nrhs < 0) {
	*info = -5;
    } else if (*ldab < (*kl << 1) + *ku + 1) {
	*info = -7;
    } else if (*ldb < std::max(1_integer,*n)) {
	*info = -10;
    }
    if (*info != 0) {
	i__1 = -(*info);
	xerbla_("DGBTRS", &i__1);
	return 0;
    }

/*     Quick return if possible */

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

    kd = *ku + *kl + 1;
    lnoti = *kl > 0;

    if (notran) {

/*        Solve  A*X = B. */

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

/*        L is represented as a product of permutations and unit lower */
/*        triangular matrices L = P(1) * L(1) * ... * P(n-1) * L(n-1), */
/*        where each transformation L(i) is a rank-one modification of */
/*        the identity matrix. */

	if (lnoti) {
	    i__1 = *n - 1;
	    for (j = 1; j <= i__1; ++j) {
/* Computing MIN */
		i__2 = *kl, i__3 = *n - j;
		lm = std::min(i__2,i__3);
		l = ipiv[j];
		if (l != j) {
		    dswap_(nrhs, &b[l + b_dim1], ldb, &b[j + b_dim1], ldb);
		}
		dger_(&lm, nrhs, &c_b7, &ab[kd + 1 + j * ab_dim1], &c__1, &b[
			j + b_dim1], ldb, &b[j + 1 + b_dim1], ldb);
/* L10: */
	    }
	}

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

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

	    i__2 = *kl + *ku;
	    dtbsv_("Upper", "No transpose", "Non-unit", n, &i__2, &ab[
		    ab_offset], ldab, &b[i__ * b_dim1 + 1], &c__1);
/* L20: */
	}

    } else {

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

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

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

	    i__2 = *kl + *ku;
	    dtbsv_("Upper", "Transpose", "Non-unit", n, &i__2, &ab[ab_offset], 
		     ldab, &b[i__ * b_dim1 + 1], &c__1);
/* L30: */
	}

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

	if (lnoti) {
	    for (j = *n - 1; j >= 1; --j) {
/* Computing MIN */
		i__1 = *kl, i__2 = *n - j;
		lm = std::min(i__1,i__2);
		dgemv_("Transpose", &lm, nrhs, &c_b7, &b[j + 1 + b_dim1], ldb, 
			 &ab[kd + 1 + j * ab_dim1], &c__1, &c_b23, &b[j + 
			b_dim1], ldb);
		l = ipiv[j];
		if (l != j) {
		    dswap_(nrhs, &b[l + b_dim1], ldb, &b[j + b_dim1], ldb);
		}
/* L40: */
	    }
	}
    }
    return 0;

/*     End of DGBTRS */

} /* dgbtrs_ */
