fixed marmousi hopefully

FWI/src/Helper/GramianBlockInverse.cpp

@@ -93,7 +93,7 @@ void GramianBlockInverse::ScalarProductInverse(Vector &b) const {
 void GramianBlockInverse::productOneCellScalarProductInverse(const Vector &u, const DGAcousticElement &elem,
                                                              Vector &b) const {
     double a = elem.Area();
-  const SparseRMatrix &SpSm = ScalarMInverse.at(a);
+  const SparseRMatrix &SpSm = ScalarMInverse.at(truncate_to_8_significant_digits(a));
   int Row = u.find_row(elem.GetCell()()).Id();
   productOneCellSparse(u, SpSm, Row, b);
 }