Correction of the solver
The system to solve is :
(I - A) x = b.
MatVectProduct(A, x, y)
gives different results :
\begin{aligned}
&\text{if \_IA = false} &\quad\rightarrow\quad &y = A x;\\
&\text{if \_IA = true} &\quad\rightarrow\quad &y = (I - A) x.
\end{aligned}
Therefore, _IA
must be set to true except for the Jacobi solver.
Indeed, the Jacobi solver uses : x_{k+1} = A x_k + b
.