文档
我要评分
获取效率
正确性
完整性
易理解
提交关闭

?syr2

Symmetric matrix rank 2 update, that is, .

Alpha is a multiplication coefficient, x and y are vectors including n elements, and A is an n x n symmetric matrix.

Interface Definition

C interface:

void cblas_ssyr2(const enum CBLAS_ORDER order, const enum CBLAS_UPLO Uplo,const BLASINT N, const float alpha, const float *X, const BLASINT incX, const float *Y, const BLASINT incY, float *A, const BLASINT lda);

void cblas_dsyr2(const enum CBLAS_ORDER order, const enum CBLAS_UPLO Uplo, const BLASINT N, const double alpha, const double *X, const BLASINT incX, const double *Y, const BLASINT incY, double *A, const BLASINT lda);

Fortran interface:

CALL SSYR2(UPLO, N, ALPHA, X, INCX, Y, INCY, A, LDA)

CALL DSYR2(UPLO, N, ALPHA, X, INCX, Y, INCY, A, LDA)

Parameters

Parameter

Type

Description

Input/Output

order

Enumeration type CBLAS_ORDER

Indicates whether the matrix is in row- or column-major order.

Input

Uplo

Enumeration type CBLAS_UPLO

Indicates whether to use the upper triangle or lower triangle of matrix A.

  • If Uplo=CblasUpper, the upper triangle of A is used.
  • If Uplo=CblasLower, the lower triangle of A is used.

Input

N

Integer

Number of elements in vector X

Input

alpha
  • For cher, alpha is of single-precision complex number type.
  • For zher, alpha is of double-precision complex number type.

Multiplication coefficient

Input

X
  • For cher, X is of single-precision complex number type.
  • For zher, X is of double-precision complex number type.

Matrix X. The length must be at least 1+(n-1)*abs(incX).

Input

incX

Integer

Increase step of vector X. The value cannot be 0.

Input

Y
  • For cher, Y is of single-precision complex number type.
  • For zher, Y is of double-precision complex number type.

Matrix Y. The length must be at least 1+(n-1)*abs(incY).

Input

incY

Integer

Increase step of vector Y. The value cannot be 0.

Input

A
  • For cher, A is of single-precision complex number type.
  • For zher, A is of double-precision complex number type.

Matrix A(lda, n)

Input/Output

lda

Integer

Length of the main dimension of matrix A. The value of lda must be greater than or equal to the value of max(1, n).

Input

Dependencies

#include "kblas.h"

Examples

C interface:

    int n = 3, lda = 4; 
    float alpha = 1.0; 
    int incx = 1, incy = 1; 
    float x[3] = {1.0, 3.0, 2.0}; 
    float y[3] = {2.0, 3.0, 2.0}; 
    /** 
     *            | 3.0  1.0   1.0  | 
     *    A    =  |  .   16.0  10.0 | 
     *            |  .    .    1.0  | 
     *            |  .    .      .  | 
     */ 
    float a[12] = {3.0, 0, 0, 0, 1.0, 16.0, 0, 0, 1.0, 10.0, 1.0, 0}; 
 
    cblas_ssyr2(CblasColMajor,CblasUpper, n, alpha, x, incx, y, incy, a, lda); 
    /*** 
     *            | 7.0  10.  7.0 | 
     *            |  .   34.  22.0| 
     * Output A = |  .    .   9.0 | 
     *            |  .    .    .  | 
     */

Fortran interface:

      INTEGER :: N=3, LDA=4 
      INTEGER :: INCX=1, INCY=1 
      REAL(4) :: ALPHA=1.0 
      REAL(4) :: X(3), Y(3), A(12) 
      DATA X/1.0, 3.0, 2.0/ 
      DATA Y/2.0, 3.0, 2.0/ 
      DATA A/3.0, 0, 0, 0, 1.0, 16.0, 0, 0, 1.0, 10.0, 1.0, 0/ 
      EXTERNAL SSYR2 
      CALL SSYR2('U', N, ALPHA, X, INCX, Y, INCY, A, LDA) 
 
*                | 7.0  10.  7.0 | 
*                |  .   34.  22.0| 
*     Output A = |  .    .   9.0 | 
*                |  .    .    .  |