Create z4c_gpu_rhs_ss.cu (reusing BSSN shell FD/chain-rule kernels):
- Uploads trKd = trK + 2*TZ to GPU so existing BSSN algebraic kernels
compute correct Z4C physical equations without modification
- New kern_z4c_post applies TZ_rhs = alpn1 * Hcon / 2, kappa1/kappa2
constraint damping, TZ advection (lopsided), and dissipation (kodis)
- Adds TZ/TZ_rhs to Meta struct, alloc/upload/download/free lifecycle
Add cuda_compute_rhs_z4c_ss() wrapper in Z4c_class.C matching the
Fortran f_compute_rhs_Z4c_ss signature, with #define redirection for
Step/SHStep call sites and #undef before analysis functions.
Add z4c_gpu_rhs_ss.o to ABE_CUDA_CFILES and build rule in makefile.
Add kappa1_c/kappa2_c constants to gpu_rhsSS_mem.h.
Build verified with USE_CUDA_Z4C=1 + WithShell — compiles and links
cleanly. All three Shell GPU files now coexist: bssn_gpu_rhs_ss.o
(BSSN), z4c_gpu_rhs_ss.o (Z4C), both sharing FD/chain-rule kernels.
Co-Authored-By: Claude Opus 4.7 <noreply@anthropic.com>
Remove the compile-time #error that blocked USE_CUDA_Z4C + WithShell.
Add GPU-to-CPU state sync at the start of both Z4C Step functions
(non-CPBC and CPBC) so shell CPU consumers read valid field data
after Cartesian GPU RHS with resident state.
Move bssn_cuda_use_resident_sync and bssn_cuda_download_level_state
_if_present from anonymous namespace to file scope in bssn_class.C
so derived classes (Z4C) can call them. Declare both in
bssn_rhs_cuda.h. Include bssn_rhs_cuda.h in Z4c_class.C.
Z4C shell RHS remains on CPU (Fortran Z4c_rhs_ss.f90) pending
future GPU kernel implementation.
Co-Authored-By: Claude Opus 4.7 <noreply@anthropic.com>
