1 files changed, 61 insertions, 0 deletions
diff --git a/Source/Parallelization/WarpXSumGuardCells.H b/Source/Parallelization/WarpXSumGuardCells.H
new file mode 100644
index 000000000..24ad1b80f
--- /dev/null
+++ b/Source/Parallelization/WarpXSumGuardCells.H
@@ -0,0 +1,61 @@
+#ifndef WARPX_SUM_GUARD_CELLS_H_
+#define WARPX_SUM_GUARD_CELLS_H_
+
+#include <AMReX_MultiFab.H>
+
+/* \brief Sum the values of `mf`, where the different boxes overlap
+ * (i.e. in the guard cells)
+ *
+ * This is typically called for the sources of the Maxwell equations (J/rho)
+ * after deposition from the macroparticles.
+ *
+ *  - When WarpX is compiled with a finite-difference scheme: this only
+ *    updates the *valid* cells of `mf`
+ *  - When WarpX is compiled with a spectral scheme (WARPX_USE_PSATD): this
+ *    updates both the *valid* cells and *guard* cells. (This is because a
+ *    spectral solver requires the value of the sources over a large stencil.)
+ */
+void
+WarpXSumGuardCells(amrex::MultiFab& mf, const amrex::Periodicity& period,
+                   const int icomp=0, const int ncomp=1){
+#ifdef WARPX_USE_PSATD
+   // Update both valid cells and guard cells
+   const amrex::IntVect n_updated_guards = mf.nGrowVect();
+#else
+   // Update only the valid cells
+   const amrex::IntVect n_updated_guards = amrex::IntVect::TheZeroVector();
+#endif
+    mf.SumBoundary(icomp, ncomp, n_updated_guards, period);
+}
+
+/* \brief Sum the values of `src` where the different boxes overlap
+ * (i.e. in the guard cells) and copy them into `dst`
+ *
+ * This is typically called for the sources of the Maxwell equations (J/rho)
+ * after deposition from the macroparticles + filtering.
+ *
+ *  - When WarpX is compiled with a finite-difference scheme: this only
+ *    updates the *valid* cells of `dst`
+ *  - When WarpX is compiled with a spectral scheme (WARPX_USE_PSATD): this
+ *    updates both the *valid* cells and *guard* cells. (This is because a
+ *    spectral solver requires the value of the sources over a large stencil.)
+ *
+ * Note: `i_comp` is the component where the results will be stored in `dst`;
+ *       The component from which we copy in `src` is always 0.
+ */
+void
+WarpXSumGuardCells(amrex::MultiFab& dst, amrex::MultiFab& src,
+                   const amrex::Periodicity& period,
+                   const int icomp=0, const int ncomp=1){
+#ifdef WARPX_USE_PSATD
+    // Update both valid cells and guard cells
+    const amrex::IntVect n_updated_guards = dst.nGrowVect();
+#else
+    // Update only the valid cells
+    const amrex::IntVect n_updated_guards = amrex::IntVect::TheZeroVector();
+#endif
+    src.SumBoundary(icomp, ncomp, n_updated_guards, period);
+    amrex::Copy( dst, src, 0, icomp, ncomp, n_updated_guards );
+}
+
+#endif // WARPX_SUM_GUARD_CELLS_H_