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opencv/3rdparty/lapack/ssyr2.c

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#include "clapack.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 */
integer i__, j, ix, iy, jx, jy, kx, ky, info;
real temp1, temp2;
extern logical lsame_(char *, char *);
extern /* Subroutine */ int xerbla_(char *, integer *);
/* .. Scalar Arguments .. */
/* .. */
/* .. Array Arguments .. */
/* .. */
/* 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. */
/* Arguments */
/* ========== */
/* 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. */
/* .. Parameters .. */
/* .. */
/* .. Local Scalars .. */
/* .. */
/* .. External Functions .. */
/* .. */
/* .. External Subroutines .. */
/* .. */
/* .. Intrinsic Functions .. */
/* .. */
/* Test the input parameters. */
/* Parameter adjustments */
--x;
--y;
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 (*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 <= i__1; ++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__ <= i__2; ++i__) {
a[i__ + j * a_dim1] = a[i__ + j * a_dim1] + x[i__] *
temp1 + y[i__] * temp2;
/* L10: */
}
}
/* L20: */
}
} else {
i__1 = *n;
for (j = 1; j <= i__1; ++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__ <= i__2; ++i__) {
a[i__ + j * a_dim1] = a[i__ + j * a_dim1] + 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 <= i__1; ++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__ <= i__2; ++i__) {
a[i__ + j * a_dim1] = a[i__ + j * a_dim1] + x[i__] *
temp1 + y[i__] * temp2;
/* L50: */
}
}
/* L60: */
}
} else {
i__1 = *n;
for (j = 1; j <= i__1; ++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__ <= i__2; ++i__) {
a[i__ + j * a_dim1] = a[i__ + j * a_dim1] + x[ix] *
temp1 + y[iy] * temp2;
ix += *incx;
iy += *incy;
/* L70: */
}
}
jx += *incx;
jy += *incy;
/* L80: */
}
}
}
return 0;
/* End of SSYR2 . */
} /* ssyr2_ */
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