[Problem] Make L2 error relative to surface area

src/sand-wedge.cc

@@ -190,11 +190,12 @@ int main(int argc, char *argv[]) {
                                   matrices.damping);
     myAssembler.assembleMass(body.getDensityField(), matrices.mass);
 
-    ScalarMatrix frictionalBoundaryMass;
+    ScalarMatrix relativeFrictionalBoundaryMass;
     myAssembler.assembleFrictionalBoundaryMass(frictionalBoundary,
-                                               frictionalBoundaryMass);
+                                               relativeFrictionalBoundaryMass);
+    relativeFrictionalBoundaryMass /= frictionalBoundary.area();
     EnergyNorm<ScalarMatrix, ScalarVector> const stateEnergyNorm(
-        frictionalBoundaryMass);
+        relativeFrictionalBoundaryMass);
 
     // Assemble forces
     Vector gravityFunctional;