zsyr.c

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/* zsyr.f -- translated by f2c (version 20061008).
   You must link the resulting object file with libf2c:
        on Microsoft Windows system, link with libf2c.lib;
        on Linux or Unix systems, link with .../path/to/libf2c.a -lm
        or, if you install libf2c.a in a standard place, with -lf2c -lm
        -- in that order, at the end of the command line, as in
                cc *.o -lf2c -lm
        Source for libf2c is in /netlib/f2c/libf2c.zip, e.g.,

                http://www.netlib.org/f2c/libf2c.zip
*/

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

/* Subroutine */ int zsyr_(char *uplo, integer *n, doublecomplex *alpha, 
        doublecomplex *x, integer *incx, doublecomplex *a, integer *lda)
{
    /* System generated locals */
    integer a_dim1, a_offset, i__1, i__2, i__3, i__4, i__5;
    doublecomplex z__1, z__2;

    /* Local variables */
    integer i__, j, ix, jx, kx, info;
    doublecomplex temp;
    extern logical lsame_(char *, char *);
    extern /* Subroutine */ int xerbla_(char *, integer *);


/*  -- LAPACK auxiliary routine (version 3.2) -- */
/*     Univ. of Tennessee, Univ. of California Berkeley and NAG Ltd.. */
/*     November 2006 */

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

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

/*  ZSYR   performs the symmetric rank 1 operation */

/*     A := alpha*x*( x' ) + A, */

/*  where alpha is a complex scalar, x is an n element vector and A is an */
/*  n by n symmetric matrix. */

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

/*  UPLO     (input) 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        (input) INTEGER */
/*           On entry, N specifies the order of the matrix A. */
/*           N must be at least zero. */
/*           Unchanged on exit. */

/*  ALPHA    (input) COMPLEX*16 */
/*           On entry, ALPHA specifies the scalar alpha. */
/*           Unchanged on exit. */

/*  X        (input) COMPLEX*16 array, 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     (input) INTEGER */
/*           On entry, INCX specifies the increment for the elements of */
/*           X. INCX must not be zero. */
/*           Unchanged on exit. */

/*  A        (input/output) COMPLEX*16 array, 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      (input) 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. */

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

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

/*     Test the input parameters. */

    /* Parameter adjustments */
    --x;
    a_dim1 = *lda;
    a_offset = 1 + a_dim1;
    a -= a_offset;

    /* 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 (*lda < max(1,*n)) {
        info = 7;
    }
    if (info != 0) {
        xerbla_("ZSYR  ", &info);
        return 0;
    }

/*     Quick return if possible. */

    if (*n == 0 || alpha->r == 0. && alpha->i == 0.) {
        return 0;
    }

/*     Set the start point in X if the increment is not unity. */

    if (*incx <= 0) {
        kx = 1 - (*n - 1) * *incx;
    } else if (*incx != 1) {
        kx = 1;
    }

/*     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 upper triangle. */

        if (*incx == 1) {
            i__1 = *n;
            for (j = 1; j <= i__1; ++j) {
                i__2 = j;
                if (x[i__2].r != 0. || x[i__2].i != 0.) {
                    i__2 = j;
                    z__1.r = alpha->r * x[i__2].r - alpha->i * x[i__2].i, 
                            z__1.i = alpha->r * x[i__2].i + alpha->i * x[i__2]
                            .r;
                    temp.r = z__1.r, temp.i = z__1.i;
                    i__2 = j;
                    for (i__ = 1; i__ <= i__2; ++i__) {
                        i__3 = i__ + j * a_dim1;
                        i__4 = i__ + j * a_dim1;
                        i__5 = i__;
                        z__2.r = x[i__5].r * temp.r - x[i__5].i * temp.i, 
                                z__2.i = x[i__5].r * temp.i + x[i__5].i * 
                                temp.r;
                        z__1.r = a[i__4].r + z__2.r, z__1.i = a[i__4].i + 
                                z__2.i;
                        a[i__3].r = z__1.r, a[i__3].i = z__1.i;
/* L10: */
                    }
                }
/* L20: */
            }
        } else {
            jx = kx;
            i__1 = *n;
            for (j = 1; j <= i__1; ++j) {
                i__2 = jx;
                if (x[i__2].r != 0. || x[i__2].i != 0.) {
                    i__2 = jx;
                    z__1.r = alpha->r * x[i__2].r - alpha->i * x[i__2].i, 
                            z__1.i = alpha->r * x[i__2].i + alpha->i * x[i__2]
                            .r;
                    temp.r = z__1.r, temp.i = z__1.i;
                    ix = kx;
                    i__2 = j;
                    for (i__ = 1; i__ <= i__2; ++i__) {
                        i__3 = i__ + j * a_dim1;
                        i__4 = i__ + j * a_dim1;
                        i__5 = ix;
                        z__2.r = x[i__5].r * temp.r - x[i__5].i * temp.i, 
                                z__2.i = x[i__5].r * temp.i + x[i__5].i * 
                                temp.r;
                        z__1.r = a[i__4].r + z__2.r, z__1.i = a[i__4].i + 
                                z__2.i;
                        a[i__3].r = z__1.r, a[i__3].i = z__1.i;
                        ix += *incx;
/* L30: */
                    }
                }
                jx += *incx;
/* L40: */
            }
        }
    } else {

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

        if (*incx == 1) {
            i__1 = *n;
            for (j = 1; j <= i__1; ++j) {
                i__2 = j;
                if (x[i__2].r != 0. || x[i__2].i != 0.) {
                    i__2 = j;
                    z__1.r = alpha->r * x[i__2].r - alpha->i * x[i__2].i, 
                            z__1.i = alpha->r * x[i__2].i + alpha->i * x[i__2]
                            .r;
                    temp.r = z__1.r, temp.i = z__1.i;
                    i__2 = *n;
                    for (i__ = j; i__ <= i__2; ++i__) {
                        i__3 = i__ + j * a_dim1;
                        i__4 = i__ + j * a_dim1;
                        i__5 = i__;
                        z__2.r = x[i__5].r * temp.r - x[i__5].i * temp.i, 
                                z__2.i = x[i__5].r * temp.i + x[i__5].i * 
                                temp.r;
                        z__1.r = a[i__4].r + z__2.r, z__1.i = a[i__4].i + 
                                z__2.i;
                        a[i__3].r = z__1.r, a[i__3].i = z__1.i;
/* L50: */
                    }
                }
/* L60: */
            }
        } else {
            jx = kx;
            i__1 = *n;
            for (j = 1; j <= i__1; ++j) {
                i__2 = jx;
                if (x[i__2].r != 0. || x[i__2].i != 0.) {
                    i__2 = jx;
                    z__1.r = alpha->r * x[i__2].r - alpha->i * x[i__2].i, 
                            z__1.i = alpha->r * x[i__2].i + alpha->i * x[i__2]
                            .r;
                    temp.r = z__1.r, temp.i = z__1.i;
                    ix = jx;
                    i__2 = *n;
                    for (i__ = j; i__ <= i__2; ++i__) {
                        i__3 = i__ + j * a_dim1;
                        i__4 = i__ + j * a_dim1;
                        i__5 = ix;
                        z__2.r = x[i__5].r * temp.r - x[i__5].i * temp.i, 
                                z__2.i = x[i__5].r * temp.i + x[i__5].i * 
                                temp.r;
                        z__1.r = a[i__4].r + z__2.r, z__1.i = a[i__4].i + 
                                z__2.i;
                        a[i__3].r = z__1.r, a[i__3].i = z__1.i;
                        ix += *incx;
/* L70: */
                    }
                }
                jx += *incx;
/* L80: */
            }
        }
    }

    return 0;

/*     End of ZSYR */

} /* zsyr_ */