#include "clapack.h"

/* Subroutine */ int dtrsm_(char *side, char *uplo, char *transa, char *diag, 
	integer *m, integer *n, doublereal *alpha, doublereal *a, integer *
	lda, doublereal *b, integer *ldb)
{
    /* System generated locals */
    integer a_dim1, a_offset, b_dim1, b_offset, i__1, i__2, i__3;

    /* Local variables */
    integer i__, j, k, info;
    doublereal temp;
    logical lside;
    extern logical lsame_(char *, char *);
    integer nrowa;
    logical upper;
    extern /* Subroutine */ int xerbla_(char *, integer *);
    logical nounit;

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

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

/*  DTRSM  solves one of the matrix equations */

/*     op( A )*X = alpha*B,   or   X*op( A ) = alpha*B, */

/*  where alpha is a scalar, X and B are m by n matrices, A is a unit, or */
/*  non-unit,  upper or lower triangular matrix  and  op( A )  is one  of */

/*     op( A ) = A   or   op( A ) = A'. */

/*  The matrix X is overwritten on B. */

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

/*  SIDE   - CHARACTER*1. */
/*           On entry, SIDE specifies whether op( A ) appears on the left */
/*           or right of X as follows: */

/*              SIDE = 'L' or 'l'   op( A )*X = alpha*B. */

/*              SIDE = 'R' or 'r'   X*op( A ) = alpha*B. */

/*           Unchanged on exit. */

/*  UPLO   - CHARACTER*1. */
/*           On entry, UPLO specifies whether the matrix A is an upper or */
/*           lower triangular matrix as follows: */

/*              UPLO = 'U' or 'u'   A is an upper triangular matrix. */

/*              UPLO = 'L' or 'l'   A is a lower triangular matrix. */

/*           Unchanged on exit. */

/*  TRANSA - CHARACTER*1. */
/*           On entry, TRANSA specifies the form of op( A ) to be used in */
/*           the matrix multiplication as follows: */

/*              TRANSA = 'N' or 'n'   op( A ) = A. */

/*              TRANSA = 'T' or 't'   op( A ) = A'. */

/*              TRANSA = 'C' or 'c'   op( A ) = A'. */

/*           Unchanged on exit. */

/*  DIAG   - CHARACTER*1. */
/*           On entry, DIAG specifies whether or not A is unit triangular */
/*           as follows: */

/*              DIAG = 'U' or 'u'   A is assumed to be unit triangular. */

/*              DIAG = 'N' or 'n'   A is not assumed to be unit */
/*                                  triangular. */

/*           Unchanged on exit. */

/*  M      - INTEGER. */
/*           On entry, M specifies the number of rows of B. M must be at */
/*           least zero. */
/*           Unchanged on exit. */

/*  N      - INTEGER. */
/*           On entry, N specifies the number of columns of B.  N must be */
/*           at least zero. */
/*           Unchanged on exit. */

/*  ALPHA  - DOUBLE PRECISION. */
/*           On entry,  ALPHA specifies the scalar  alpha. When  alpha is */
/*           zero then  A is not referenced and  B need not be set before */
/*           entry. */
/*           Unchanged on exit. */

/*  A      - DOUBLE PRECISION array of DIMENSION ( LDA, k ), where k is m */
/*           when  SIDE = 'L' or 'l'  and is  n  when  SIDE = 'R' or 'r'. */
/*           Before entry  with  UPLO = 'U' or 'u',  the  leading  k by k */
/*           upper triangular part of the array  A must contain the upper */
/*           triangular matrix  and the strictly lower triangular part of */
/*           A is not referenced. */
/*           Before entry  with  UPLO = 'L' or 'l',  the  leading  k by k */
/*           lower triangular part of the array  A must contain the lower */
/*           triangular matrix  and the strictly upper triangular part of */
/*           A is not referenced. */
/*           Note that when  DIAG = 'U' or 'u',  the diagonal elements of */
/*           A  are not referenced either,  but are assumed to be  unity. */
/*           Unchanged on exit. */

/*  LDA    - INTEGER. */
/*           On entry, LDA specifies the first dimension of A as declared */
/*           in the calling (sub) program.  When  SIDE = 'L' or 'l'  then */
/*           LDA  must be at least  max( 1, m ),  when  SIDE = 'R' or 'r' */
/*           then LDA must be at least max( 1, n ). */
/*           Unchanged on exit. */

/*  B      - DOUBLE PRECISION array of DIMENSION ( LDB, n ). */
/*           Before entry,  the leading  m by n part of the array  B must */
/*           contain  the  right-hand  side  matrix  B,  and  on exit  is */
/*           overwritten by the solution matrix  X. */

/*  LDB    - INTEGER. */
/*           On entry, LDB specifies the first dimension of B as declared */
/*           in  the  calling  (sub)  program.   LDB  must  be  at  least */
/*           max( 1, m ). */
/*           Unchanged on exit. */


/*  Level 3 Blas routine. */


/*  -- Written on 8-February-1989. */
/*     Jack Dongarra, Argonne National Laboratory. */
/*     Iain Duff, AERE Harwell. */
/*     Jeremy Du Croz, Numerical Algorithms Group Ltd. */
/*     Sven Hammarling, Numerical Algorithms Group Ltd. */


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

/*     Test the input parameters. */

    /* Parameter adjustments */
    a_dim1 = *lda;
    a_offset = 1 + a_dim1;
    a -= a_offset;
    b_dim1 = *ldb;
    b_offset = 1 + b_dim1;
    b -= b_offset;

    /* Function Body */
    lside = lsame_(side, "L");
    if (lside) {
	nrowa = *m;
    } else {
	nrowa = *n;
    }
    nounit = lsame_(diag, "N");
    upper = lsame_(uplo, "U");

    info = 0;
    if (! lside && ! lsame_(side, "R")) {
	info = 1;
    } else if (! upper && ! lsame_(uplo, "L")) {
	info = 2;
    } else if (! lsame_(transa, "N") && ! lsame_(transa, 
	     "T") && ! lsame_(transa, "C")) {
	info = 3;
    } else if (! lsame_(diag, "U") && ! lsame_(diag, 
	    "N")) {
	info = 4;
    } else if (*m < 0) {
	info = 5;
    } else if (*n < 0) {
	info = 6;
    } else if (*lda < max(1,nrowa)) {
	info = 9;
    } else if (*ldb < max(1,*m)) {
	info = 11;
    }
    if (info != 0) {
	xerbla_("DTRSM ", &info);
	return 0;
    }

/*     Quick return if possible. */

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

/*     And when  alpha.eq.zero. */

    if (*alpha == 0.) {
	i__1 = *n;
	for (j = 1; j <= i__1; ++j) {
	    i__2 = *m;
	    for (i__ = 1; i__ <= i__2; ++i__) {
		b[i__ + j * b_dim1] = 0.;
/* L10: */
	    }
/* L20: */
	}
	return 0;
    }

/*     Start the operations. */

    if (lside) {
	if (lsame_(transa, "N")) {

/*           Form  B := alpha*inv( A )*B. */

	    if (upper) {
		i__1 = *n;
		for (j = 1; j <= i__1; ++j) {
		    if (*alpha != 1.) {
			i__2 = *m;
			for (i__ = 1; i__ <= i__2; ++i__) {
			    b[i__ + j * b_dim1] = *alpha * b[i__ + j * b_dim1]
				    ;
/* L30: */
			}
		    }
		    for (k = *m; k >= 1; --k) {
			if (b[k + j * b_dim1] != 0.) {
			    if (nounit) {
				b[k + j * b_dim1] /= a[k + k * a_dim1];
			    }
			    i__2 = k - 1;
			    for (i__ = 1; i__ <= i__2; ++i__) {
				b[i__ + j * b_dim1] -= b[k + j * b_dim1] * a[
					i__ + k * a_dim1];
/* L40: */
			    }
			}
/* L50: */
		    }
/* L60: */
		}
	    } else {
		i__1 = *n;
		for (j = 1; j <= i__1; ++j) {
		    if (*alpha != 1.) {
			i__2 = *m;
			for (i__ = 1; i__ <= i__2; ++i__) {
			    b[i__ + j * b_dim1] = *alpha * b[i__ + j * b_dim1]
				    ;
/* L70: */
			}
		    }
		    i__2 = *m;
		    for (k = 1; k <= i__2; ++k) {
			if (b[k + j * b_dim1] != 0.) {
			    if (nounit) {
				b[k + j * b_dim1] /= a[k + k * a_dim1];
			    }
			    i__3 = *m;
			    for (i__ = k + 1; i__ <= i__3; ++i__) {
				b[i__ + j * b_dim1] -= b[k + j * b_dim1] * a[
					i__ + k * a_dim1];
/* L80: */
			    }
			}
/* L90: */
		    }
/* L100: */
		}
	    }
	} else {

/*           Form  B := alpha*inv( A' )*B. */

	    if (upper) {
		i__1 = *n;
		for (j = 1; j <= i__1; ++j) {
		    i__2 = *m;
		    for (i__ = 1; i__ <= i__2; ++i__) {
			temp = *alpha * b[i__ + j * b_dim1];
			i__3 = i__ - 1;
			for (k = 1; k <= i__3; ++k) {
			    temp -= a[k + i__ * a_dim1] * b[k + j * b_dim1];
/* L110: */
			}
			if (nounit) {
			    temp /= a[i__ + i__ * a_dim1];
			}
			b[i__ + j * b_dim1] = temp;
/* L120: */
		    }
/* L130: */
		}
	    } else {
		i__1 = *n;
		for (j = 1; j <= i__1; ++j) {
		    for (i__ = *m; i__ >= 1; --i__) {
			temp = *alpha * b[i__ + j * b_dim1];
			i__2 = *m;
			for (k = i__ + 1; k <= i__2; ++k) {
			    temp -= a[k + i__ * a_dim1] * b[k + j * b_dim1];
/* L140: */
			}
			if (nounit) {
			    temp /= a[i__ + i__ * a_dim1];
			}
			b[i__ + j * b_dim1] = temp;
/* L150: */
		    }
/* L160: */
		}
	    }
	}
    } else {
	if (lsame_(transa, "N")) {

/*           Form  B := alpha*B*inv( A ). */

	    if (upper) {
		i__1 = *n;
		for (j = 1; j <= i__1; ++j) {
		    if (*alpha != 1.) {
			i__2 = *m;
			for (i__ = 1; i__ <= i__2; ++i__) {
			    b[i__ + j * b_dim1] = *alpha * b[i__ + j * b_dim1]
				    ;
/* L170: */
			}
		    }
		    i__2 = j - 1;
		    for (k = 1; k <= i__2; ++k) {
			if (a[k + j * a_dim1] != 0.) {
			    i__3 = *m;
			    for (i__ = 1; i__ <= i__3; ++i__) {
				b[i__ + j * b_dim1] -= a[k + j * a_dim1] * b[
					i__ + k * b_dim1];
/* L180: */
			    }
			}
/* L190: */
		    }
		    if (nounit) {
			temp = 1. / a[j + j * a_dim1];
			i__2 = *m;
			for (i__ = 1; i__ <= i__2; ++i__) {
			    b[i__ + j * b_dim1] = temp * b[i__ + j * b_dim1];
/* L200: */
			}
		    }
/* L210: */
		}
	    } else {
		for (j = *n; j >= 1; --j) {
		    if (*alpha != 1.) {
			i__1 = *m;
			for (i__ = 1; i__ <= i__1; ++i__) {
			    b[i__ + j * b_dim1] = *alpha * b[i__ + j * b_dim1]
				    ;
/* L220: */
			}
		    }
		    i__1 = *n;
		    for (k = j + 1; k <= i__1; ++k) {
			if (a[k + j * a_dim1] != 0.) {
			    i__2 = *m;
			    for (i__ = 1; i__ <= i__2; ++i__) {
				b[i__ + j * b_dim1] -= a[k + j * a_dim1] * b[
					i__ + k * b_dim1];
/* L230: */
			    }
			}
/* L240: */
		    }
		    if (nounit) {
			temp = 1. / a[j + j * a_dim1];
			i__1 = *m;
			for (i__ = 1; i__ <= i__1; ++i__) {
			    b[i__ + j * b_dim1] = temp * b[i__ + j * b_dim1];
/* L250: */
			}
		    }
/* L260: */
		}
	    }
	} else {

/*           Form  B := alpha*B*inv( A' ). */

	    if (upper) {
		for (k = *n; k >= 1; --k) {
		    if (nounit) {
			temp = 1. / a[k + k * a_dim1];
			i__1 = *m;
			for (i__ = 1; i__ <= i__1; ++i__) {
			    b[i__ + k * b_dim1] = temp * b[i__ + k * b_dim1];
/* L270: */
			}
		    }
		    i__1 = k - 1;
		    for (j = 1; j <= i__1; ++j) {
			if (a[j + k * a_dim1] != 0.) {
			    temp = a[j + k * a_dim1];
			    i__2 = *m;
			    for (i__ = 1; i__ <= i__2; ++i__) {
				b[i__ + j * b_dim1] -= temp * b[i__ + k * 
					b_dim1];
/* L280: */
			    }
			}
/* L290: */
		    }
		    if (*alpha != 1.) {
			i__1 = *m;
			for (i__ = 1; i__ <= i__1; ++i__) {
			    b[i__ + k * b_dim1] = *alpha * b[i__ + k * b_dim1]
				    ;
/* L300: */
			}
		    }
/* L310: */
		}
	    } else {
		i__1 = *n;
		for (k = 1; k <= i__1; ++k) {
		    if (nounit) {
			temp = 1. / a[k + k * a_dim1];
			i__2 = *m;
			for (i__ = 1; i__ <= i__2; ++i__) {
			    b[i__ + k * b_dim1] = temp * b[i__ + k * b_dim1];
/* L320: */
			}
		    }
		    i__2 = *n;
		    for (j = k + 1; j <= i__2; ++j) {
			if (a[j + k * a_dim1] != 0.) {
			    temp = a[j + k * a_dim1];
			    i__3 = *m;
			    for (i__ = 1; i__ <= i__3; ++i__) {
				b[i__ + j * b_dim1] -= temp * b[i__ + k * 
					b_dim1];
/* L330: */
			    }
			}
/* L340: */
		    }
		    if (*alpha != 1.) {
			i__2 = *m;
			for (i__ = 1; i__ <= i__2; ++i__) {
			    b[i__ + k * b_dim1] = *alpha * b[i__ + k * b_dim1]
				    ;
/* L350: */
			}
		    }
/* L360: */
		}
	    }
	}
    }

    return 0;

/*     End of DTRSM . */

} /* dtrsm_ */