How to perform Vector-Matrix Multiplication with BLAS ? -

How to perform Vector-Matrix Multiplication with BLAS ? -

blas defines gemv (matrix-vector multiplication) level-2 operation. how utilize blas library perform vector-matrix multiplication ?

it's obvious, don't see how utilize blas operation multiplication. have expected gevm operation.

the matrix-vector multiplication of (m x n) matrix (n x 1) vector result (m x 1) vector. in short a*a(mxn)*x(nx1) + b*y(mx1) -> y(mx1). of course of study can utilize incx , incy when vector included in matrix.

in order define vector-matrix multiplication vector should transposed. i.e. a*x(1xm)*a(mxn) + b*y(1xn) -> y(1xn). not have vector single row matrix.

starting point there 2 possibilities.

either utilize level-3 "gemm"

?gemm(transa, transb, m, n, k, alpha, a, lda, b, ldb, beta, c, ldc)

using

?gemm('n', 'n', 1, n, m, a, x, 1, a, m, b, y, 1)

or more math. considering (x*a)^t = a^t * x^t row matrix x converted vector x^t(mx1). y transpose vector y^t(nx1). of course of study memory-wise both x , x^t store same way, sequentially. means can utilize 1 time again gemv using transpose matrix a

?gemv('t', m, n, a, a, m, x, 1, b, y, 1)

matrix matrix-multiplication blas