title: Using Eigen BICGSTAB in Parallel to solve the sparse matrix
body: <p>I am trying to solve a linear system of equations of the form <code>Ax=b</code> with the Eigen BICGSTAB in parallel.</p>
  
  <pre><code>initParallel();
  int n=4;
  omp_set_num_threads(n);
  setNbThreads(n);
  
  BiCGSTAB  &lt;SparseMatrix&lt;double&gt;&gt; solver;
  solver.compute(A);
  x = solver.solve(b);    
  </code></pre>
  
  <p>I also enable the OpenMP in the visual studio. but I can't see any increase in CPU usage when I increase the number of thread. As a results I cannot see any enhancement in its performance.  </p>
  
  <p>However, When I used LeastSquaresConjugateGradient as a solver, the CPU usage increases when I increase the number of threads, that means I could successfully parallel it, but as I said it does not work for BiCGSTAB.</p>
  
  <pre><code>initParallel();
  int n=4;
  omp_set_num_threads(n);
  setNbThreads(n);
  
  LeastSquaresConjugateGradient &lt;SparseMatrix&lt;double&gt;&gt; solver;
  solver.compute(A);
  x = solver.solve(b);
  </code></pre>
  
  <p>anyone can advise me why it is not paralleled for BiCGSTAB and how can do that?</p>