函数语法:
XGER( M, N, ALPHA, X, INCX, Y, INCY, A, LDA)
功能：
GER performs the rank 1 operation
A := alpha*x*y' + A,
C programming language version of SGER method with row primary order data storage.
源代码：
/* Purpose: SGER computes A := alpha*x*y' + A. Discussion: SGER performs the rank 1 operation A := alpha*x*y' + A, where alpha is a scalar, x is an m element vector, y is an n element vector and A is an m by n matrix. Licensing: This code is distributed under the GNU LGPL license. Modified: 2017 Author: Original FORTRAN77 version by Jack Dongarra, Jeremy Du Croz, Sven Hammarling, Richard Hanson. This C version by Chunfeng Yang, John Burkardt. Parameters: Input, int M, the number of rows of the matrix A. 0 <= M. Input, int N, the number of columns of the matrix A. 0 <= N. Input, float ALPHA, the scalar multiplier. Input, float X[1+(M-1)*abs(INCX)], the first vector. Input, int INCX, the increment for elements of X. INCX must not be zero. Input, float Y[1+(N-1)*abs(INCY)], the second vector. Input, int INCY, the increment for elements of Y. INCY must not be zero. Input/output, float A[LDA*N]. On entry, the leading M by N part of the array contains the matrix of coefficients. On exit, A is overwritten by the updated matrix. Input, int LDA, the first dimension of A as declared in the calling program. max ( 1, M ) <= LDA. */ // row prinary order version void cblas_sger ( int m, int n, float alpha, float x[], int incx, float y[], int incy, float a[], int lda ) { //int i; int info; int ix = 0; //int j; int jy = 0; int kx; int ky = 0; float temp = 0.0; /* Test the input parameters. */ info = 0; if (m < 0) { info = 1; } else if (n < 0) { info = 2; } else if (incx == 0) { info = 5; } else if (incy == 0) { info = 7; } else if (lda < i4_max(1, m)) { info = 9; } if (info != 0) { xerbla("SGER", info); return; } /* Quick return if possible. */ if (m == 0 || n == 0 || alpha == 0.0) { return; } /* Start the operations. In this version the elements of A are accessed sequentially with one pass through A. */ if (0 < incx) { ix = 0; } else { ix = 0 - (m - 1) * incx; } if (incy == 1) { for (int i = 0; i < m; i++) { if (x[ix] != 0.0) { temp = alpha * x[ix]; for (int j = 0; j < n; j++) { a[i * lda + j] = a[i * lda + j] + y[j] * temp; } } ix = ix + incx; } } else { if (0 < incy) { ky = 0; } else { ky = 0 - (m - 1) * incy; } for (int i = 0; i < m; i++) { if (x[ix] != 0.0) { temp = alpha * x[ix]; jy = ky; for (int j = 0; j < n; j++) { a[i * lda + j] = a[i * lda + j] + y[jy] * temp; jy = jy + incy; } } ix = ix + incx; } } return; }
Testing Code
void testsger() { int row = 4; int column = 4; float *A = (float*) malloc(row * column * sizeof(float)); float *x = (float*) malloc(row * sizeof(float)); float *y = (float*) malloc(column * sizeof(float)); for (int i = 0; i < row; i++) { for (int j = 0; j < column; j++) { A[i*row + j] = 0.0; } x[i] = 1.0 + i; y[i] = 1.0 + i; } cblas_sger(row/2, column/2, 1.0, x, 2, y, 2, &A[1*row+2], row); show_matrix(A, row, column); return; }
Testing Results:
A = 1.0 * X * Y X = [ 1, 2 , 3 , 4 ] Y = [1,2,3,4] A: 0.000000 0.000000 0.000000 0.000000 0.000000 0.000000 1.000000 3.000000 0.000000 0.000000 3.000000 9.000000 0.000000 0.000000 0.000000 0.000000
