/*  -- translated by f2c (version 19940927).

   You must link the resulting object file with the libraries:

	-lf2c -lm   (in that order)

*/

#include "f2c.h"

/* Subroutine */ int ssyr2_(char *uplo, integer *n, real *alpha, real *x, 

	integer *incx, real *y, integer *incy, real *a, integer *lda)

{

    /* System generated locals */

    integer a_dim1, a_offset, i__1, i__2;

    /* Local variables */

    static integer info;

    static real temp1, temp2;

    static integer i, j;

    extern logical lsame_(char *, char *);

    static integer ix, iy, jx, jy, kx, ky;

    extern /* Subroutine */ int xerbla_(char *, integer *);

/*  Purpose   

    =======   

    SSYR2  performs the symmetric rank 2 operation   

       A := alpha*x*y' + alpha*y*x' + A,   

    where alpha is a scalar, x and y are n element vectors and A is an n 

    by n symmetric matrix.   

    Parameters   

    ==========   

    UPLO   - CHARACTER*1.   

             On entry, UPLO specifies whether the upper or lower   

             triangular part of the array A is to be referenced as   

             follows:   

                UPLO = 'U' or 'u'   Only the upper triangular part of A   

                                    is to be referenced.   

                UPLO = 'L' or 'l'   Only the lower triangular part of A   

                                    is to be referenced.   

             Unchanged on exit.   

    N      - INTEGER.   

             On entry, N specifies the order of the matrix A.   

             N must be at least zero.   

             Unchanged on exit.   

    ALPHA  - REAL            .   

             On entry, ALPHA specifies the scalar alpha.   

             Unchanged on exit.   

    X      - REAL             array of dimension at least   

             ( 1 + ( n - 1 )*abs( INCX ) ).   

             Before entry, the incremented array X must contain the n   

             element vector x.   

             Unchanged on exit.   

    INCX   - INTEGER.   

             On entry, INCX specifies the increment for the elements of   

             X. INCX must not be zero.   

             Unchanged on exit.   

    Y      - REAL             array of dimension at least   

             ( 1 + ( n - 1 )*abs( INCY ) ).   

             Before entry, the incremented array Y must contain the n   

             element vector y.   

             Unchanged on exit.   

    INCY   - INTEGER.   

             On entry, INCY specifies the increment for the elements of   

             Y. INCY must not be zero.   

             Unchanged on exit.   

    A      - REAL             array of DIMENSION ( LDA, n ).   

             Before entry with  UPLO = 'U' or 'u', the leading n by n   

             upper triangular part of the array A must contain the upper 

             triangular part of the symmetric matrix and the strictly   

             lower triangular part of A is not referenced. On exit, the   

             upper triangular part of the array A 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 A must contain the lower 

             triangular part of the symmetric matrix and the strictly   

             upper triangular part of A is not referenced. On exit, the   

             lower triangular part of the array A is overwritten by the   

             lower triangular part of the updated matrix.   

    LDA    - INTEGER.   

             On entry, LDA specifies the first dimension of A as declared 

             in the calling (sub) program. LDA must be at least   

             max( 1, n ).   

             Unchanged on exit.   

    Level 2 Blas routine.   

    -- Written on 22-October-1986.   

       Jack Dongarra, Argonne National Lab.   

       Jeremy Du Croz, Nag Central Office.   

       Sven Hammarling, Nag Central Office.   

       Richard Hanson, Sandia National Labs.   

       Test the input parameters.   

   Parameter adjustments   

       Function Body */

#define X(I) x[(I)-1]

#define Y(I) y[(I)-1]

#define A(I,J) a[(I)-1 + ((J)-1)* ( *lda)]

    info = 0;

    if (! lsame_(uplo, "U") && ! lsame_(uplo, "L")) {

	info = 1;

    } else if (*n < 0) {

	info = 2;

    } else if (*incx == 0) {

	info = 5;

    } else if (*incy == 0) {

	info = 7;

    } else if (*lda < max(1,*n)) {

	info = 9;

    }

    if (info != 0) {

	xerbla_("SSYR2 ", &info);

	return 0;

    }

/*     Quick return if possible. */

    if (*n == 0 || *alpha == 0.f) {

	return 0;

    }

/*     Set up the start points in X and Y if the increments are not both 

       unity. */

    if (*incx != 1 || *incy != 1) {

	if (*incx > 0) {

	    kx = 1;

	} else {

	    kx = 1 - (*n - 1) * *incx;

	}

	if (*incy > 0) {

	    ky = 1;

	} else {

	    ky = 1 - (*n - 1) * *incy;

	}

	jx = kx;

	jy = ky;

    }

/*     Start the operations. In this version the elements of A are   

       accessed sequentially with one pass through the triangular part   

       of A. */

    if (lsame_(uplo, "U")) {

/*        Form  A  when A is stored in the upper triangle. */

	if (*incx == 1 && *incy == 1) {

	    i__1 = *n;

	    for (j = 1; j <= *n; ++j) {

		if (X(j) != 0.f || Y(j) != 0.f) {

		    temp1 = *alpha * Y(j);

		    temp2 = *alpha * X(j);

		    i__2 = j;

		    for (i = 1; i <= j; ++i) {

			A(i,j) = A(i,j) + X(i) * temp1 

				+ Y(i) * temp2;

/* L10: */

		    }

		}

/* L20: */

	    }

	} else {

	    i__1 = *n;

	    for (j = 1; j <= *n; ++j) {

		if (X(jx) != 0.f || Y(jy) != 0.f) {

		    temp1 = *alpha * Y(jy);

		    temp2 = *alpha * X(jx);

		    ix = kx;

		    iy = ky;

		    i__2 = j;

		    for (i = 1; i <= j; ++i) {

			A(i,j) = A(i,j) + X(ix) * temp1 

				+ Y(iy) * temp2;

			ix += *incx;

			iy += *incy;

/* L30: */

		    }

		}

		jx += *incx;

		jy += *incy;

/* L40: */

	    }

	}

    } else {

/*        Form  A  when A is stored in the lower triangle. */

	if (*incx == 1 && *incy == 1) {

	    i__1 = *n;

	    for (j = 1; j <= *n; ++j) {

		if (X(j) != 0.f || Y(j) != 0.f) {

		    temp1 = *alpha * Y(j);

		    temp2 = *alpha * X(j);

		    i__2 = *n;

		    for (i = j; i <= *n; ++i) {

			A(i,j) = A(i,j) + X(i) * temp1 

				+ Y(i) * temp2;

/* L50: */

		    }

		}

/* L60: */

	    }

	} else {

	    i__1 = *n;

	    for (j = 1; j <= *n; ++j) {

		if (X(jx) != 0.f || Y(jy) != 0.f) {

		    temp1 = *alpha * Y(jy);

		    temp2 = *alpha * X(jx);

		    ix = jx;

		    iy = jy;

		    i__2 = *n;

		    for (i = j; i <= *n; ++i) {

			A(i,j) = A(i,j) + X(ix) * temp1 

				+ Y(iy) * temp2;

			ix += *incx;

			iy += *incy;

/* L70: */

		    }

		}

		jx += *incx;

		jy += *incy;

/* L80: */

	    }

	}

    }

    return 0;

/*     End of SSYR2 . */

} /* ssyr2_ */