environment variables in setup.py for AVX512 and FFP_CONTRACT_OFF to …

…avoid clang issue

setup.py

@@ -25,6 +25,20 @@
     vars = sysconfig.get_config_vars()
     vars['LDSHARED'] = vars['LDSHARED'].replace('-bundle', '-shared')
     extra_link_args=['-Wl,-install_name,@rpath/librebound'+suffix]
+
+# Default compile args
+extra_compile_args=['-fstrict-aliasing', '-O3','-std=c99','-Wno-unknown-pragmas', ghash_arg, '-DLIBREBOUND', '-D_GNU_SOURCE', '-fPIC']
+
+# Option to disable FMA in CLANG. 
+FFP_CONTRACT_OFF = os.environ.get("FFP_CONTRACT_OFF", None)
+if FFP_CONTRACT_OFF:
+    extra_compile_args.append('-ffp-contract=off')
+
+# Option to enable AVX512 enabled integrators (WHFast512). 
+AVX512 = os.environ.get("AVX512", None)
+if AVX512:
+    extra_compile_args.append('-march=native')
+    extra_compile_args.append('-DAVX512')
 
 libreboundmodule = Extension('librebound',
                     sources = [ 'src/rebound.c',
@@ -57,11 +71,8 @@
                                 ],
                     include_dirs = ['src'],
                     define_macros=[ ('LIBREBOUND', None) ],
-                    # Uncomment the following line for the non-AVX512 version of REBOUND
-                    extra_compile_args=['-fstrict-aliasing', '-O3','-std=c99','-Wno-unknown-pragmas', ghash_arg, '-DLIBREBOUND', '-D_GNU_SOURCE', '-fPIC'],
-                    # Uncomment the following line to enable AVX512 
-                    # extra_compile_args=['-fstrict-aliasing', '-O3','-std=c99','-Wno-unknown-pragmas', ghash_arg, '-DLIBREBOUND', '-D_GNU_SOURCE', '-fPIC', '-march=native', '-DAVX512'],
                     extra_link_args=extra_link_args,
+                    extra_compile_args=extra_compile_args,
                     )
 
 here = os.path.abspath(os.path.dirname(__file__))