Add parallelism using OpenMP

Closes the-virtual-brain#10

setup.py

@@ -60,6 +60,11 @@
     compiler_directives["linetrace"] = True
     define_macros.append(("CYTHON_TRACE_NOGIL", "1"))
 
+
+if sys.platform == "darwin":
+    os.environ["CC"] = "/usr/local/opt/llvm/bin/clang -L/usr/local/opt/llvm/lib -Wl,-rpath,/usr/local/opt/llvm/lib"
+    os.environ["CXX"] = "/usr/local/opt/llvm/bin/clang++ -L/usr/local/opt/llvm/lib -Wl,-rpath,/usr/local/opt/llvm/lib"
+
 GEODESIC_NAME = "gdist"
 
 GEODESIC_MODULE = [
@@ -68,7 +73,7 @@
         sources=["gdist.pyx"],  # Filename of Cython source
         language="c++",  # Cython create C++ source
         # Disable assertions; one is failing geodesic_mesh.h:405
-        define_macros=define_macros,
+        define_macros=[('NDEBUG', 1)],
         extra_compile_args=[
             '--std=c++14',
             '/openmp' if sys.platform == 'win32' else '-fopenmp',