216 lines
6.4 KiB
C
216 lines
6.4 KiB
C
#include "blaswrap.h"
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#ifdef __cplusplus
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extern "C" {
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#endif
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#include "f2c.h"
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/* Subroutine */ int dspr2_(char *uplo, integer *n, doublereal *alpha,
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doublereal *x, integer *incx, doublereal *y, integer *incy,
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doublereal *ap)
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{
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/* System generated locals */
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integer 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, k;
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extern logical lsame_(char *, char *);
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static integer kk, 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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DSPR2 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
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n by n symmetric matrix, supplied in packed form.
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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 matrix A is supplied in the packed
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array AP as follows:
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UPLO = 'U' or 'u' The upper triangular part of A is
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supplied in AP.
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UPLO = 'L' or 'l' The lower triangular part of A is
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supplied in AP.
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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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AP - DOUBLE PRECISION array of DIMENSION at least
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( ( n*( n + 1 ) )/2 ).
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Before entry with UPLO = 'U' or 'u', the array AP must
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contain the upper triangular part of the symmetric matrix
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packed sequentially, column by column, so that AP( 1 )
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contains a( 1, 1 ), AP( 2 ) and AP( 3 ) contain a( 1, 2 )
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and a( 2, 2 ) respectively, and so on. On exit, the array
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AP is overwritten by the upper triangular part of the
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updated matrix.
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Before entry with UPLO = 'L' or 'l', the array AP must
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contain the lower triangular part of the symmetric matrix
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packed sequentially, column by column, so that AP( 1 )
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contains a( 1, 1 ), AP( 2 ) and AP( 3 ) contain a( 2, 1 )
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and a( 3, 1 ) respectively, and so on. On exit, the array
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AP is overwritten by the lower triangular part of the
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updated matrix.
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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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--ap;
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--y;
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--x;
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/* Function Body */
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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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}
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if (info != 0) {
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xerbla_("DSPR2 ", &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 the array AP
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are accessed sequentially with one pass through AP. */
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kk = 1;
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if (lsame_(uplo, "U")) {
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/* Form A when upper triangle is stored in AP. */
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if (*incx == 1 && *incy == 1) {
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i__1 = *n;
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for (j = 1; j <= i__1; ++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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k = kk;
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i__2 = j;
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for (i__ = 1; i__ <= i__2; ++i__) {
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ap[k] = ap[k] + x[i__] * temp1 + y[i__] * temp2;
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++k;
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/* L10: */
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}
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}
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kk += j;
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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 <= i__1; ++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 = kk + j - 1;
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for (k = kk; k <= i__2; ++k) {
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ap[k] = ap[k] + x[ix] * temp1 + 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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kk += j;
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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 lower triangle is stored in AP. */
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if (*incx == 1 && *incy == 1) {
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i__1 = *n;
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for (j = 1; j <= i__1; ++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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k = kk;
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i__2 = *n;
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for (i__ = j; i__ <= i__2; ++i__) {
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ap[k] = ap[k] + x[i__] * temp1 + y[i__] * temp2;
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++k;
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/* L50: */
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}
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}
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kk = kk + *n - j + 1;
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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 <= i__1; ++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 = kk + *n - j;
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for (k = kk; k <= i__2; ++k) {
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ap[k] = ap[k] + x[ix] * temp1 + 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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kk = kk + *n - j + 1;
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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 DSPR2 . */
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} /* dspr2_ */
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#ifdef __cplusplus
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}
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#endif
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