#include "blaswrap.h"
#include "f2c.h"

/* Subroutine */ int dspr2_(char *uplo, integer *n, doublereal *alpha, 
	doublereal *x, integer *incx, doublereal *y, integer *incy, 
	doublereal *ap)
{
    /* System generated locals */
    integer i__1, i__2;
    /* Local variables */
    static integer info;
    static doublereal temp1, temp2;
    static integer i__, j, k;
    extern logical lsame_(char *, char *);
    static integer kk, ix, iy, jx, jy, kx, ky;
    extern /* Subroutine */ int xerbla_(char *, integer *);
/*  Purpose   
    =======   
    DSPR2  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, supplied in packed form.   
    Parameters   
    ==========   
    UPLO   - CHARACTER*1.   
             On entry, UPLO specifies whether the upper or lower   
             triangular part of the matrix A is supplied in the packed   
             array AP as follows:   
                UPLO = 'U' or 'u'   The upper triangular part of A is   
                                    supplied in AP.   
                UPLO = 'L' or 'l'   The lower triangular part of A is   
                                    supplied in AP.   
             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  - DOUBLE PRECISION.   
             On entry, ALPHA specifies the scalar alpha.   
             Unchanged on exit.   
    X      - DOUBLE PRECISION 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      - DOUBLE PRECISION 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.   
    AP     - DOUBLE PRECISION array of DIMENSION at least   
             ( ( n*( n + 1 ) )/2 ).   
             Before entry with  UPLO = 'U' or 'u', the array AP must   
             contain the upper triangular part of the symmetric matrix   
             packed sequentially, column by column, so that AP( 1 )   
             contains a( 1, 1 ), AP( 2 ) and AP( 3 ) contain a( 1, 2 )   
             and a( 2, 2 ) respectively, and so on. On exit, the array   
             AP is overwritten by the upper triangular part of the   
             updated matrix.   
             Before entry with UPLO = 'L' or 'l', the array AP must   
             contain the lower triangular part of the symmetric matrix   
             packed sequentially, column by column, so that AP( 1 )   
             contains a( 1, 1 ), AP( 2 ) and AP( 3 ) contain a( 2, 1 )   
             and a( 3, 1 ) respectively, and so on. On exit, the array   
             AP is overwritten by the lower triangular part of the   
             updated matrix.   
    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 */
    --ap;
    --y;
    --x;
    /* Function Body */
    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;
    }
    if (info != 0) {
	xerbla_("DSPR2 ", &info);
	return 0;
    }
/*     Quick return if possible. */
    if (*n == 0 || *alpha == 0.) {
	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 the array AP   
       are accessed sequentially with one pass through AP. */
    kk = 1;
    if (lsame_(uplo, "U")) {
/*        Form  A  when upper triangle is stored in AP. */
	if (*incx == 1 && *incy == 1) {
	    i__1 = *n;
	    for (j = 1; j <= i__1; ++j) {
		if (x[j] != 0. || y[j] != 0.) {
		    temp1 = *alpha * y[j];
		    temp2 = *alpha * x[j];
		    k = kk;
		    i__2 = j;
		    for (i__ = 1; i__ <= i__2; ++i__) {
			ap[k] = ap[k] + x[i__] * temp1 + y[i__] * temp2;
			++k;
/* L10: */
		    }
		}
		kk += j;
/* L20: */
	    }
	} else {
	    i__1 = *n;
	    for (j = 1; j <= i__1; ++j) {
		if (x[jx] != 0. || y[jy] != 0.) {
		    temp1 = *alpha * y[jy];
		    temp2 = *alpha * x[jx];
		    ix = kx;
		    iy = ky;
		    i__2 = kk + j - 1;
		    for (k = kk; k <= i__2; ++k) {
			ap[k] = ap[k] + x[ix] * temp1 + y[iy] * temp2;
			ix += *incx;
			iy += *incy;
/* L30: */
		    }
		}
		jx += *incx;
		jy += *incy;
		kk += j;
/* L40: */
	    }
	}
    } else {
/*        Form  A  when lower triangle is stored in AP. */
	if (*incx == 1 && *incy == 1) {
	    i__1 = *n;
	    for (j = 1; j <= i__1; ++j) {
		if (x[j] != 0. || y[j] != 0.) {
		    temp1 = *alpha * y[j];
		    temp2 = *alpha * x[j];
		    k = kk;
		    i__2 = *n;
		    for (i__ = j; i__ <= i__2; ++i__) {
			ap[k] = ap[k] + x[i__] * temp1 + y[i__] * temp2;
			++k;
/* L50: */
		    }
		}
		kk = kk + *n - j + 1;
/* L60: */
	    }
	} else {
	    i__1 = *n;
	    for (j = 1; j <= i__1; ++j) {
		if (x[jx] != 0. || y[jy] != 0.) {
		    temp1 = *alpha * y[jy];
		    temp2 = *alpha * x[jx];
		    ix = jx;
		    iy = jy;
		    i__2 = kk + *n - j;
		    for (k = kk; k <= i__2; ++k) {
			ap[k] = ap[k] + x[ix] * temp1 + y[iy] * temp2;
			ix += *incx;
			iy += *incy;
/* L70: */
		    }
		}
		jx += *incx;
		jy += *incy;
		kk = kk + *n - j + 1;
/* L80: */
	    }
	}
    }
    return 0;
/*     End of DSPR2 . */
} /* dspr2_ */

