imex: Fix inclusion of FAS corrections in residuals.

Signed-off-by: Matthew Emmett <[email protected]>

Author: memmett

include/pfasst/encap/imex_sweeper.hpp

@@ -208,9 +208,11 @@ namespace pfasst
             dst[m]->saxpy(-1.0, this->state[m]);
           }
           if (this->fas_corrections.size() > 0) {
-            size_t m0 = this->quadrature->left_is_node() ? 1 : 0;
-            for (size_t m = m0; m < this->quadrature->get_num_nodes(); m++) {
-                dst[m]->saxpy(1.0, this->fas_corrections[m-m0]);
+            // XXX: build a matrix and use mat_apply to do this
+            for (size_t m = 0; m < this->quadrature->get_num_nodes(); m++) {
+              for (size_t n = 0; n <= m; n++) {
+                dst[m]->saxpy(1.0, this->fas_corrections[n]);
+              }
             }
           }
           dst[0]->mat_apply(dst, dt, this->quadrature->get_q_mat(), this->fs_expl, false);