[Libmesh-users] How to multiply DenseMatrix by DenseVector in LibMesh?

[John P. <pet...@cf...>]

Shengli Xu writes:
 > Hi,
 > DenseVector a,b;
 > DenseMatrix C;
 > How to multiply "transpose(a)*C*b" in LibMesh?
 > Thank you!

I don't see an interface for multiplying a dense matrix
by a dense vector.  For the time being, you'll have to do
it by hand, the old-fashioned way, with loops.

transpose(x)*y is the same thing as x . y (dot product).
Here's a pseudocode


DenseVector temp;

for i
  for j
    temp(i) += C(i,j)*b(j);
  end
end

Real sum=0;
for i
  sum += a(i) * temp1(i);
end