message: resolve b being overwritten
diff: @@ -84,13 +84,16 @@ int main(int argc, char *argv[])
  x->copy_from(host_x.get());
  b->copy_from(host_x.get());
  - // Calculate initial residual
  + // Calculate initial residual by overwriting b
  auto one = gko::initialize<vec>({1.0}, exec);
  auto neg_one = gko::initialize<vec>({-1.0}, exec);
  auto initres = gko::initialize<vec>({0.0}, exec);
  A->apply(lend(one), lend(x), lend(neg_one), lend(b));
  b->compute_norm2(lend(initres));
  + // copy b again
  + b->copy_from(host_x.get());
  +
  auto iter_stop =
  gko::stop::Iteration::build().with_max_iters(10000u).on(exec);
  auto tol_stop = gko::stop::ResidualNormReduction<ValueType>::build()
  