Increase NUM_THREADS on Windows to match other platforms

Author: ndabas

CHANGELOG.md

@@ -6,6 +6,8 @@
   This fixes a crash in the default allocator's overflow area: overflow slots
   re-mapped a new buffer on every allocation and eventually wrote past the end
   of `new_release_info`. Seen on Windows ARM64 with many concurrent callers.
+- raise `NUM_THREADS` from 24 to 64 on Windows (amd64 and arm64), matching
+  the Linux and macOS builds.
 
 ### 0.3.34.481.0 (2026-10-20)
 

tools/build_steps_win_arm64.bat

@@ -161,7 +161,7 @@ cmake .. -G Ninja ^
  -DSYMBOLPREFIX="scipy_" ^
  -DLIBNAMEPREFIX="scipy_" ^
  -DUSE_THREADS=1 ^
- -DNUM_THREADS=24 ^
+ -DNUM_THREADS=64 ^
  %interface_flags%
 
 if errorlevel 1 exit /b 1

tools/build_steps_windows.sh

@@ -106,7 +106,7 @@ sed -e "s/^VERSION = .*/VERSION = ${version}/" -i.bak Makefile.rule
 # Build OpenBLAS
 CFLAGS="$CFLAGS -fvisibility=protected -fno-ident" \
 make BINARY=$build_bits DYNAMIC_ARCH=1 USE_THREAD=1 USE_OPENMP=0 \
-     NUM_THREADS=24 NO_WARMUP=1 NO_AFFINITY=1 CONSISTENT_FPCSR=1 \
+     NUM_THREADS=64 NO_WARMUP=1 NO_AFFINITY=1 CONSISTENT_FPCSR=1 \
      BUILD_LAPACK_DEPRECATED=1 TARGET=PRESCOTT BUFFERSIZE=20 \
      LDFLAGS="$LDFLAGS" \
      DYNAMIC_LIST="$dynamic_list" \