265 lines
6.6 KiB
C
265 lines
6.6 KiB
C
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/* -- translated by f2c (version 19940927).
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You must link the resulting object file with the libraries:
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-lf2c -lm (in that order)
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*/
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#include "f2c.h"
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/* Subroutine */ int dsyr2_(char *uplo, integer *n, doublereal *alpha,
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doublereal *x, integer *incx, doublereal *y, integer *incy,
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doublereal *a, integer *lda)
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{
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/* System generated locals */
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integer a_dim1, a_offset, i__1, i__2;
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/* Local variables */
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static integer info;
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static doublereal temp1, temp2;
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static integer i, j;
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extern logical lsame_(char *, char *);
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static integer ix, iy, jx, jy, kx, ky;
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extern /* Subroutine */ int xerbla_(char *, integer *);
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/* Purpose
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=======
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DSYR2 performs the symmetric rank 2 operation
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A := alpha*x*y' + alpha*y*x' + A,
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where alpha is a scalar, x and y are n element vectors and A is an n
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by n symmetric matrix.
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Parameters
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==========
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UPLO - CHARACTER*1.
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On entry, UPLO specifies whether the upper or lower
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triangular part of the array A is to be referenced as
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follows:
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UPLO = 'U' or 'u' Only the upper triangular part of A
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is to be referenced.
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UPLO = 'L' or 'l' Only the lower triangular part of A
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is to be referenced.
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Unchanged on exit.
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N - INTEGER.
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On entry, N specifies the order of the matrix A.
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N must be at least zero.
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Unchanged on exit.
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ALPHA - DOUBLE PRECISION.
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On entry, ALPHA specifies the scalar alpha.
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Unchanged on exit.
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X - DOUBLE PRECISION array of dimension at least
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( 1 + ( n - 1 )*abs( INCX ) ).
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Before entry, the incremented array X must contain the n
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element vector x.
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Unchanged on exit.
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INCX - INTEGER.
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On entry, INCX specifies the increment for the elements of
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X. INCX must not be zero.
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Unchanged on exit.
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Y - DOUBLE PRECISION array of dimension at least
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( 1 + ( n - 1 )*abs( INCY ) ).
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Before entry, the incremented array Y must contain the n
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element vector y.
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Unchanged on exit.
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INCY - INTEGER.
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On entry, INCY specifies the increment for the elements of
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Y. INCY must not be zero.
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Unchanged on exit.
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A - DOUBLE PRECISION array of DIMENSION ( LDA, n ).
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Before entry with UPLO = 'U' or 'u', the leading n by n
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upper triangular part of the array A must contain the upper
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triangular part of the symmetric matrix and the strictly
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lower triangular part of A is not referenced. On exit, the
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upper triangular part of the array A is overwritten by the
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upper triangular part of the updated matrix.
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Before entry with UPLO = 'L' or 'l', the leading n by n
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lower triangular part of the array A must contain the lower
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triangular part of the symmetric matrix and the strictly
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upper triangular part of A is not referenced. On exit, the
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lower triangular part of the array A is overwritten by the
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lower triangular part of the updated matrix.
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LDA - INTEGER.
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On entry, LDA specifies the first dimension of A as declared
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in the calling (sub) program. LDA must be at least
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max( 1, n ).
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Unchanged on exit.
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Level 2 Blas routine.
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-- Written on 22-October-1986.
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Jack Dongarra, Argonne National Lab.
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Jeremy Du Croz, Nag Central Office.
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Sven Hammarling, Nag Central Office.
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Richard Hanson, Sandia National Labs.
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Test the input parameters.
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Parameter adjustments
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Function Body */
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#define X(I) x[(I)-1]
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#define Y(I) y[(I)-1]
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#define A(I,J) a[(I)-1 + ((J)-1)* ( *lda)]
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info = 0;
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if (! lsame_(uplo, "U") && ! lsame_(uplo, "L")) {
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info = 1;
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} else if (*n < 0) {
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info = 2;
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} else if (*incx == 0) {
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info = 5;
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} else if (*incy == 0) {
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info = 7;
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} else if (*lda < max(1,*n)) {
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info = 9;
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}
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if (info != 0) {
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xerbla_("DSYR2 ", &info);
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return 0;
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}
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/* Quick return if possible. */
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if (*n == 0 || *alpha == 0.) {
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return 0;
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}
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/* Set up the start points in X and Y if the increments are not both
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unity. */
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if (*incx != 1 || *incy != 1) {
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if (*incx > 0) {
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kx = 1;
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} else {
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kx = 1 - (*n - 1) * *incx;
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}
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if (*incy > 0) {
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ky = 1;
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} else {
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ky = 1 - (*n - 1) * *incy;
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}
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jx = kx;
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jy = ky;
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}
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/* Start the operations. In this version the elements of A are
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accessed sequentially with one pass through the triangular part
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of A. */
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if (lsame_(uplo, "U")) {
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/* Form A when A is stored in the upper triangle. */
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if (*incx == 1 && *incy == 1) {
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i__1 = *n;
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for (j = 1; j <= *n; ++j) {
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if (X(j) != 0. || Y(j) != 0.) {
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temp1 = *alpha * Y(j);
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temp2 = *alpha * X(j);
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i__2 = j;
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for (i = 1; i <= j; ++i) {
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A(i,j) = A(i,j) + X(i) * temp1
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+ Y(i) * temp2;
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/* L10: */
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}
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}
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/* L20: */
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}
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} else {
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i__1 = *n;
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for (j = 1; j <= *n; ++j) {
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if (X(jx) != 0. || Y(jy) != 0.) {
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temp1 = *alpha * Y(jy);
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temp2 = *alpha * X(jx);
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ix = kx;
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iy = ky;
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i__2 = j;
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for (i = 1; i <= j; ++i) {
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A(i,j) = A(i,j) + X(ix) * temp1
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+ Y(iy) * temp2;
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ix += *incx;
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iy += *incy;
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/* L30: */
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}
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}
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jx += *incx;
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jy += *incy;
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/* L40: */
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}
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}
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} else {
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/* Form A when A is stored in the lower triangle. */
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if (*incx == 1 && *incy == 1) {
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i__1 = *n;
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for (j = 1; j <= *n; ++j) {
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if (X(j) != 0. || Y(j) != 0.) {
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temp1 = *alpha * Y(j);
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temp2 = *alpha * X(j);
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i__2 = *n;
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for (i = j; i <= *n; ++i) {
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A(i,j) = A(i,j) + X(i) * temp1
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+ Y(i) * temp2;
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/* L50: */
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}
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}
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/* L60: */
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}
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} else {
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i__1 = *n;
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for (j = 1; j <= *n; ++j) {
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if (X(jx) != 0. || Y(jy) != 0.) {
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temp1 = *alpha * Y(jy);
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temp2 = *alpha * X(jx);
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ix = jx;
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iy = jy;
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i__2 = *n;
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for (i = j; i <= *n; ++i) {
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A(i,j) = A(i,j) + X(ix) * temp1
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+ Y(iy) * temp2;
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ix += *incx;
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iy += *incy;
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/* L70: */
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}
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}
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jx += *incx;
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jy += *incy;
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/* L80: */
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}
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}
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}
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return 0;
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/* End of DSYR2 . */
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} /* dsyr2_ */
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