added helper

src/problem/Formulation.h

@@ -224,6 +224,9 @@ namespace gmshfem::problem
     common::Memory getEstimatedFactorizationDistributedMemoryUsage(bool chol = false, bool sum = false) const;
     void infoMemoryDistributed(bool chol) const;
     virtual unsigned long long getNumberOfNonZeros() const;
+    const system::MatrixFactory< T_Scalar >* getMatrixFactory() const {
+      return _A;
+    }
 
     // Pre-processing
     virtual common::Timer pre(const DofsSort::Algorithm algo = common::Options::instance()->dofsSortAlgorithm);