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>
