Add lopsided_kodis subroutine in lopsidediff.f90 that combines upwind
advection (lopsided) and Kreiss-Oliger dissipation (kodis) into one
function sharing a single fh buffer from symmetry_bd. This eliminates
27 redundant full-grid copies per RHS evaluation (108 per timestep).
For gxx/gyy/gzz variables: kodis stencil coefficients sum to zero
(1-6+15-20+15-6+1=0), so using gxx(=dxx+1) instead of dxx for the
dissipation buffer is mathematically exact.
Update bssn_rhs.f90 to use the merged lopsided_kodis calls.
Co-authored-by: ianchb <45872450+ianchb@users.noreply.github.com>
Wrap the NaN sanity check (21 sum() full-array traversals per RHS call)
with #ifdef DEBUG so it is compiled out in production builds.
This eliminates 84 redundant full-array scans per timestep (21 per RHS
call × 4 RK4 substages) that serve no purpose when input data is valid.
Usage:
- Production build (default): NaN check is disabled, no changes needed.
- Debug build: add -DDEBUG to f90appflags in makefile.inc, e.g.
f90appflags = -O3 ... -DDEBUG -fpp ...
to re-enable the NaN sanity check.
Co-Authored-By: Claude Opus 4.6 <noreply@anthropic.com>
