Added SNESFormResidual

Author: rezgarshakeri

examples/Hdiv-mixed/include/matops.h

@@ -8,6 +8,7 @@
 
 PetscErrorCode ApplyLocal_Ceed(User user, Vec X, Vec Y);
 PetscErrorCode MatMult_Ceed(Mat A, Vec X, Vec Y);
+PetscErrorCode SNESFormResidual_Ceed(SNES snes, Vec X, Vec Y, void *ctx);
 PetscErrorCode ComputeError(User user, Vec X, CeedVector target,
                             CeedScalar *l2_error_u, CeedScalar *l2_error_p);
 

examples/Hdiv-mixed/main.c

@@ -88,7 +88,7 @@ int main(int argc, char **argv) {
   CeedMemType mem_type_backend;
   CeedGetPreferredMemType(ceed, &mem_type_backend);
   // ---------------------------------------------------------------------------
-  // Set-up DM
+  // Setup DM
   // ---------------------------------------------------------------------------
   // PETSc objects
   DM             dm;

examples/Hdiv-mixed/src/matops.c

@@ -2,8 +2,8 @@
 #include "../include/setup-libceed.h"
 
 // -----------------------------------------------------------------------------
-// This function uses libCEED to compute the action of the Laplacian with
-// Dirichlet boundary conditions
+// Apply the local action of a libCEED operator and store result in PETSc vector
+// i.e. compute A X = Y
 // -----------------------------------------------------------------------------
 PetscErrorCode ApplyLocal_Ceed(User user, Vec X, Vec Y) {
   PetscScalar *x, *y;
@@ -55,6 +55,25 @@ PetscErrorCode MatMult_Ceed(Mat A, Vec X, Vec Y) {
   PetscFunctionReturn(0);
 };
 
+// -----------------------------------------------------------------------------
+// This function uses libCEED to compute the non-linear residual
+// -----------------------------------------------------------------------------
+PetscErrorCode SNESFormResidual_Ceed(SNES snes, Vec X, Vec Y, void *ctx) {
+  User user = (User)ctx;
+
+  PetscFunctionBeginUser;
+
+  // Use computed BCs
+  PetscCall( VecZeroEntries(user->X_loc) );
+  PetscCall( DMPlexInsertBoundaryValues(user->dm, PETSC_TRUE, user->X_loc,
+                                        1.0, NULL, NULL, NULL) );
+
+  // libCEED for local action of residual evaluator
+  PetscCall( ApplyLocalCeedOp(X, Y, user) );
+
+  PetscFunctionReturn(0);
+};
+
 // -----------------------------------------------------------------------------
 // This function calculates the error in the final solution
 // -----------------------------------------------------------------------------