/* dsyr2k.f -- translated by f2c (version of 23 April 1993  18:34:30).
   You must link the resulting object file with the libraries:
	-lf2c -lm   (in that order)
*/

#include "f2c.h"

/* Subroutine */ int dsyr2k_(uplo, trans, n, k, alpha, a, lda, b, ldb, beta, 
	c, ldc, uplo_len, trans_len)
char *uplo, *trans;
integer *n, *k;
doublereal *alpha, *a;
integer *lda;
doublereal *b;
integer *ldb;
doublereal *beta, *c;
integer *ldc;
ftnlen uplo_len;
ftnlen trans_len;
{
    /* System generated locals */
    integer a_dim1, a_offset, b_dim1, b_offset, c_dim1, c_offset, i__1, i__2, 
	    i__3;

    /* Local variables */
    static integer info;
    static doublereal temp1, temp2;
    static integer i, j, l;
    extern logical lsame_();
    static integer nrowa;
    static logical upper;
    extern /* Subroutine */ int xerbla_();

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

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

/*  DSYR2K  performs one of the symmetric rank 2k operations */

/*     C := alpha*A*B' + alpha*B*A' + beta*C, */

/*  or */

/*     C := alpha*A'*B + alpha*B'*A + beta*C, */

/*  where  alpha and beta  are scalars, C is an  n by n  symmetric matrix 
*/
/*  and  A and B  are  n by k  matrices  in the  first  case  and  k by n 
*/
/*  matrices in the second case. */

/*  Parameters */
/*  ========== */

/*  UPLO   - CHARACTER*1. */
/*           On  entry,   UPLO  specifies  whether  the  upper  or  lower 
*/
/*           triangular  part  of the  array  C  is to be  referenced  as 
*/
/*           follows: */

/*              UPLO = 'U' or 'u'   Only the  upper triangular part of  C 
*/
/*                                  is to be referenced. */

/*              UPLO = 'L' or 'l'   Only the  lower triangular part of  C 
*/
/*                                  is to be referenced. */

/*           Unchanged on exit. */

/*  TRANS  - CHARACTER*1. */
/*           On entry,  TRANS  specifies the operation to be performed as 
*/
/*           follows: */

/*              TRANS = 'N' or 'n'   C := alpha*A*B' + alpha*B*A' + */
/*                                        beta*C. */

/*              TRANS = 'T' or 't'   C := alpha*A'*B + alpha*B'*A + */
/*                                        beta*C. */

/*              TRANS = 'C' or 'c'   C := alpha*A'*B + alpha*B'*A + */
/*                                        beta*C. */

/*           Unchanged on exit. */

/*  N      - INTEGER. */
/*           On entry,  N specifies the order of the matrix C.  N must be 
*/
/*           at least zero. */
/*           Unchanged on exit. */

/*  K      - INTEGER. */
/*           On entry with  TRANS = 'N' or 'n',  K  specifies  the number 
*/
/*           of  columns  of the  matrices  A and B,  and on  entry  with 
*/
/*           TRANS = 'T' or 't' or 'C' or 'c',  K  specifies  the  number 
*/
/*           of rows of the matrices  A and B.  K must be at least  zero. 
*/
/*           Unchanged on exit. */

/*  ALPHA  - DOUBLE PRECISION. */
/*           On entry, ALPHA specifies the scalar alpha. */
/*           Unchanged on exit. */

/*  A      - DOUBLE PRECISION array of DIMENSION ( LDA, ka ), where ka is 
*/
/*           k  when  TRANS = 'N' or 'n',  and is  n  otherwise. */
/*           Before entry with  TRANS = 'N' or 'n',  the  leading  n by k 
*/
/*           part of the array  A  must contain the matrix  A,  otherwise 
*/
/*           the leading  k by n  part of the array  A  must contain  the 
*/
/*           matrix A. */
/*           Unchanged on exit. */

/*  LDA    - INTEGER. */
/*           On entry, LDA specifies the first dimension of A as declared 
*/
/*           in  the  calling  (sub)  program.   When  TRANS = 'N' or 'n' 
*/
/*           then  LDA must be at least  max( 1, n ), otherwise  LDA must 
*/
/*           be at least  max( 1, k ). */
/*           Unchanged on exit. */

/*  B      - DOUBLE PRECISION array of DIMENSION ( LDB, kb ), where kb is 
*/
/*           k  when  TRANS = 'N' or 'n',  and is  n  otherwise. */
/*           Before entry with  TRANS = 'N' or 'n',  the  leading  n by k 
*/
/*           part of the array  B  must contain the matrix  B,  otherwise 
*/
/*           the leading  k by n  part of the array  B  must contain  the 
*/
/*           matrix B. */
/*           Unchanged on exit. */

/*  LDB    - INTEGER. */
/*           On entry, LDB specifies the first dimension of B as declared 
*/
/*           in  the  calling  (sub)  program.   When  TRANS = 'N' or 'n' 
*/
/*           then  LDB must be at least  max( 1, n ), otherwise  LDB must 
*/
/*           be at least  max( 1, k ). */
/*           Unchanged on exit. */

/*  BETA   - DOUBLE PRECISION. */
/*           On entry, BETA specifies the scalar beta. */
/*           Unchanged on exit. */

/*  C      - DOUBLE PRECISION array of DIMENSION ( LDC, n ). */
/*           Before entry  with  UPLO = 'U' or 'u',  the leading  n by n 
*/
/*           upper triangular part of the array C must contain the upper 
*/
/*           triangular part  of the  symmetric matrix  and the strictly 
*/
/*           lower triangular part of C is not referenced.  On exit, the 
*/
/*           upper triangular part of the array  C is overwritten by the 
*/
/*           upper triangular part of the updated matrix. */
/*           Before entry  with  UPLO = 'L' or 'l',  the leading  n by n 
*/
/*           lower triangular part of the array C must contain the lower 
*/
/*           triangular part  of the  symmetric matrix  and the strictly 
*/
/*           upper triangular part of C is not referenced.  On exit, the 
*/
/*           lower triangular part of the array  C is overwritten by the 
*/
/*           lower triangular part of the updated matrix. */

/*  LDC    - INTEGER. */
/*           On entry, LDC specifies the first dimension of C as declared 
*/
/*           in  the  calling  (sub)  program.   LDC  must  be  at  least 
*/
/*           max( 1, n ). */
/*           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 .. */
/*     .. */
/*     .. Executable Statements .. */

/*     Test the input parameters. */

    /* Parameter adjustments */
    c_dim1 = *ldc;
    c_offset = c_dim1 + 1;
    c -= c_offset;
    b_dim1 = *ldb;
    b_offset = b_dim1 + 1;
    b -= b_offset;
    a_dim1 = *lda;
    a_offset = a_dim1 + 1;
    a -= a_offset;

    /* Function Body */
    if (lsame_(trans, "N", 1L, 1L)) {
	nrowa = *n;
    } else {
	nrowa = *k;
    }
    upper = lsame_(uplo, "U", 1L, 1L);

    info = 0;
    if (! upper && ! lsame_(uplo, "L", 1L, 1L)) {
	info = 1;
    } else if (! lsame_(trans, "N", 1L, 1L) && ! lsame_(trans, "T", 1L, 1L) &&
	     ! lsame_(trans, "C", 1L, 1L)) {
	info = 2;
    } else if (*n < 0) {
	info = 3;
    } else if (*k < 0) {
	info = 4;
    } else if (*lda < max(1,nrowa)) {
	info = 7;
    } else if (*ldb < max(1,nrowa)) {
	info = 9;
    } else if (*ldc < max(1,*n)) {
	info = 12;
    }
    if (info != 0) {
	xerbla_("DSYR2K", &info, 6L);
	return 0;
    }

/*     Quick return if possible. */

    if (*n == 0 || (*alpha == 0. || *k == 0) && *beta == 1.) {
	return 0;
    }

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

    if (*alpha == 0.) {
	if (upper) {
	    if (*beta == 0.) {
		i__1 = *n;
		for (j = 1; j <= i__1; ++j) {
		    i__2 = j;
		    for (i = 1; i <= i__2; ++i) {
			c[i + j * c_dim1] = 0.;
/* L10: */
		    }
/* L20: */
		}
	    } else {
		i__1 = *n;
		for (j = 1; j <= i__1; ++j) {
		    i__2 = j;
		    for (i = 1; i <= i__2; ++i) {
			c[i + j * c_dim1] = *beta * c[i + j * c_dim1];
/* L30: */
		    }
/* L40: */
		}
	    }
	} else {
	    if (*beta == 0.) {
		i__1 = *n;
		for (j = 1; j <= i__1; ++j) {
		    i__2 = *n;
		    for (i = j; i <= i__2; ++i) {
			c[i + j * c_dim1] = 0.;
/* L50: */
		    }
/* L60: */
		}
	    } else {
		i__1 = *n;
		for (j = 1; j <= i__1; ++j) {
		    i__2 = *n;
		    for (i = j; i <= i__2; ++i) {
			c[i + j * c_dim1] = *beta * c[i + j * c_dim1];
/* L70: */
		    }
/* L80: */
		}
	    }
	}
	return 0;
    }

/*     Start the operations. */

    if (lsame_(trans, "N", 1L, 1L)) {

/*        Form  C := alpha*A*B' + alpha*B*A' + C. */

	if (upper) {
	    i__1 = *n;
	    for (j = 1; j <= i__1; ++j) {
		if (*beta == 0.) {
		    i__2 = j;
		    for (i = 1; i <= i__2; ++i) {
			c[i + j * c_dim1] = 0.;
/* L90: */
		    }
		} else if (*beta != 1.) {
		    i__2 = j;
		    for (i = 1; i <= i__2; ++i) {
			c[i + j * c_dim1] = *beta * c[i + j * c_dim1];
/* L100: */
		    }
		}
		i__2 = *k;
		for (l = 1; l <= i__2; ++l) {
		    if (a[j + l * a_dim1] != 0. || b[j + l * b_dim1] != 0.) {
			temp1 = *alpha * b[j + l * b_dim1];
			temp2 = *alpha * a[j + l * a_dim1];
			i__3 = j;
			for (i = 1; i <= i__3; ++i) {
			    c[i + j * c_dim1] = c[i + j * c_dim1] + a[i + l * 
				    a_dim1] * temp1 + b[i + l * b_dim1] * 
				    temp2;
/* L110: */
			}
		    }
/* L120: */
		}
/* L130: */
	    }
	} else {
	    i__1 = *n;
	    for (j = 1; j <= i__1; ++j) {
		if (*beta == 0.) {
		    i__2 = *n;
		    for (i = j; i <= i__2; ++i) {
			c[i + j * c_dim1] = 0.;
/* L140: */
		    }
		} else if (*beta != 1.) {
		    i__2 = *n;
		    for (i = j; i <= i__2; ++i) {
			c[i + j * c_dim1] = *beta * c[i + j * c_dim1];
/* L150: */
		    }
		}
		i__2 = *k;
		for (l = 1; l <= i__2; ++l) {
		    if (a[j + l * a_dim1] != 0. || b[j + l * b_dim1] != 0.) {
			temp1 = *alpha * b[j + l * b_dim1];
			temp2 = *alpha * a[j + l * a_dim1];
			i__3 = *n;
			for (i = j; i <= i__3; ++i) {
			    c[i + j * c_dim1] = c[i + j * c_dim1] + a[i + l * 
				    a_dim1] * temp1 + b[i + l * b_dim1] * 
				    temp2;
/* L160: */
			}
		    }
/* L170: */
		}
/* L180: */
	    }
	}
    } else {

/*        Form  C := alpha*A'*B + alpha*B'*A + C. */

	if (upper) {
	    i__1 = *n;
	    for (j = 1; j <= i__1; ++j) {
		i__2 = j;
		for (i = 1; i <= i__2; ++i) {
		    temp1 = 0.;
		    temp2 = 0.;
		    i__3 = *k;
		    for (l = 1; l <= i__3; ++l) {
			temp1 += a[l + i * a_dim1] * b[l + j * b_dim1];
			temp2 += b[l + i * b_dim1] * a[l + j * a_dim1];
/* L190: */
		    }
		    if (*beta == 0.) {
			c[i + j * c_dim1] = *alpha * temp1 + *alpha * temp2;
		    } else {
			c[i + j * c_dim1] = *beta * c[i + j * c_dim1] + *
				alpha * temp1 + *alpha * temp2;
		    }
/* L200: */
		}
/* L210: */
	    }
	} else {
	    i__1 = *n;
	    for (j = 1; j <= i__1; ++j) {
		i__2 = *n;
		for (i = j; i <= i__2; ++i) {
		    temp1 = 0.;
		    temp2 = 0.;
		    i__3 = *k;
		    for (l = 1; l <= i__3; ++l) {
			temp1 += a[l + i * a_dim1] * b[l + j * b_dim1];
			temp2 += b[l + i * b_dim1] * a[l + j * a_dim1];
/* L220: */
		    }
		    if (*beta == 0.) {
			c[i + j * c_dim1] = *alpha * temp1 + *alpha * temp2;
		    } else {
			c[i + j * c_dim1] = *beta * c[i + j * c_dim1] + *
				alpha * temp1 + *alpha * temp2;
		    }
/* L230: */
		}
/* L240: */
	    }
	}
    }

    return 0;

/*     End of DSYR2K. */

} /* dsyr2k_ */

