vector-matrix product

anacondgame — Wed, 04 Jul 2007 10:40:05 GMT

Hi,

I have need to implement the vector-matrix product (not matrix-vector product).
which function can I use?

I have tried with dgemv (with the parameter trans = 112) but it doesn't work.
I have the following matrix and vectors:

  x	= -1.2  -0.8  1.0


	    0	 0.4  0.6

 M 	=  -0.4	 0    0.4

 	   -0.6	 0    0.6

I wont compute x*M as M'*x' .

M'*v' = -0.28 -0.48 -0.44

This is the code example:

double alpha = 1.0;

double beta = 0.0;

int incx = 1;

int incy = 1;

CBLAS_ORDER order = CblasRowMajor;

CBLAS_TRANSPOSE trans = CblasTrans;

int r = 3;

int c = 3;

int lda = 3;


cblas_dgemv(order,trans,r,c,alpha,M,lda,x,incx,beta,y,incy);

But the result "y" is incorrect !!?
The result y is following:

y = (-2656984258037080400000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000.0, 94150893907688424300000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000.0, 0.0)

Help me!

Re: vector-matrix product

Intel_C_Intel — Thu, 19 Jul 2007 12:21:25 GMT

I don't see anything about y in your code. Remember that dgemv does the following operation:

y = alpha*A*x + beta*y.

y must be a vector. To get the values you seek, y must by zeroed.

I tried this out using sgemv (not the cblas version) and got the answers you think you should get.

If you still have problems, I will look at this anew.

Bruce

topic Re: vector-matrix product in Intel® oneAPI Math Kernel Library

vector-matrix product

Re: vector-matrix product