Charge deposition skips bounds check

[WeiqunZhang]

Summary

• WarpXParticleContainer::DepositCharge in Particles/WarpXParticleContainer.cpp:1485-1489 and again in the overload at 1816-1820 tries to guard against depositing into a component that was never allocated.
• The guard compares rho->nComp() >= icomp - 1, which is always true because icomp is non-negative. The check never fails, so requests for component 1 (used for the “new” charge) succeed even when rho_fp only allocated one component.
• When do_dive_cleaning is disabled (the default), rho_fp has a single component. The subsequent alias MultiFab rhoi(*rho, amrex::make_alias, icomp*nc, nc); therefore indexes past the end of the allocation and lockAdd writes out-of-bounds. On GPU this manifests as miscomputed charge and intermittent crashes.

Suggested patch

diff --git a/Particles/WarpXParticleContainer.cpp b/Particles/WarpXParticleContainer.cpp
@@
-    WARPX_ALWAYS_ASSERT_WITH_MESSAGE(
-        rho->nComp() >= icomp - 1,
+    WARPX_ALWAYS_ASSERT_WITH_MESSAGE(
+        rho->nComp() >= (icomp + 1) * WarpX::ncomps,
         "Cannot deposit charge in rho component icomp=" + std::to_string(icomp) +
         ": not enough components allocated (" + std::to_string(rho->nComp()) + "!"
     );
@@
-    WARPX_ALWAYS_ASSERT_WITH_MESSAGE(
-        rho->nComp() >= icomp - 1,
+    WARPX_ALWAYS_ASSERT_WITH_MESSAGE(
+        rho->nComp() >= (icomp + 1) * WarpX::ncomps,
         "Cannot deposit charge in rho component icomp=" + std::to_string(icomp) +
         ": not enough components allocated (" + std::to_string(rho->nComp()) + "!"
     );

Prepared by Codex