Update fftw

Author: rpep

bin/install-fftw.sh

@@ -3,7 +3,7 @@
 # This script installs FFTW locally. It may need to environment
 # variables to work, like 'export CC=gcc' in ARCHER.
 
-FFTW=fftw-3.3.8
+FFTW=fftw-3.3.10
 
 set -e
 

fidimag/common/dipolar/demag.c

@@ -479,7 +479,9 @@ void finalize_plan(fft_demag_plan *restrict plan) {
   fftw_free(plan->hy);
   fftw_free(plan->hz);
 
-  fftw_cleanup_threads();
+  // Note: fftw_cleanup_threads() is a global cleanup function and should
+  // NOT be called per-object. It should only be called once at program exit.
+  // Calling it here causes crashes when multiple FFTDemag objects are used.
 
   free(plan);
 }