TPZMatRed::MultAdd implementation needs review

[thiagoquinelato]

MultAdd implementations attempts to multiply matrices with vectors with incompatible dimensions (e.g., lines 507 and 518):

l. 507: fK01.Multiply(x,l_Res,0);

l. 518: fK11.Multiply(x,l_ResFinal,0);

Also, fSolver's usage drops const qualifier.

[philippedevloo]

fK01 and fK11 have the same number of columns. This means the lines 507 and 518 are not incompatible. What this method computes is alpha *(K11 - K10 * K00^-1 * K01) x + beta y

[philippedevloo]

I agreee that the solve method drops the const qualifier. I can't think of a way to work around it. After all, the solve method is usually direct and, if K00 is not decomposed yet, it will decompose K00. A second call to Solve will obviously not modify the matrix...

[orlandini]

We've seen that the only moment when fIsReduced is checked is at the beginning of TPZMatRed::MultAdd, to decide whether the method should behave as alpha *(K11 - K10 * K00^-1 * K01) x + beta y or alpha *K x + beta y.

Would there be a problem if we were to invert K00 in TPZMatRed::SetReduced? This would eliminate the need to call the Solve method in TPZMatRed::MultAdd...

[philippedevloo]

We could conceive a method Solve() const which generates a DebugStop() if the matrix is not decomposed?