basic ffi demo - candidate for python3

howto_compile_win64.txt

@@ -19,6 +19,10 @@ setenv /x64 /release
 ... and "python setup.py build" should work
 
 
+# Using compiler from microsoft for python 2.7 I seem to need this for cffi
+
+set VS90COMNTOOLS="C:\Users\wright\AppData\Local\Programs\Common\Microsoft\Visual C++ for Python\9.0"
+
 =========== Using mingwpy ===============
 
 pip install -i https://pypi.anaconda.org/carlkl/simple mingwpy

src/build_ffi_demo.py

@@ -0,0 +1,35 @@
+# Try some interfacing via cffi ...
+
+from cffi import FFI
+
+
+ffi = FFI()
+ffi.set_source(
+    "_ffi_diffraction",
+    r"""
+#include "omp.h"
+
+double sum(double numbers[],int num_elements){
+   int i;
+   double s=0.0;
+#pragma omp parallel for reduction(+: s)
+   for (i=0; i<num_elements; i++)
+   {
+     s = s + numbers[i];
+   }
+   return s;
+}
+    """,
+    Libraries = [] ,
+    extra_compile_args = ["/openmp",], 
+    extra_link_args = [], 
+    )
+
+
+ffi.cdef("""     
+double sum(double [],int);
+""")
+
+if __name__ == "__main__":
+    ffi.compile(verbose=True)
+

src/run_ffi_demo.py

@@ -0,0 +1,27 @@
+
+
+# Try some interfacing via cffi ...
+
+from _ffi_diffraction import ffi, lib
+import numpy as np
+import time
+np.random.seed(42)
+#       1K    1M     1G
+size = 128 * 1024 * 1024 * 0.5
+ar = np.random.random( int(size) ) 
+
+print ar.shape
+
+N=100
+start = time.clock()
+for i in range(N):
+    s = lib.sum( ffi.cast('double *', ar.ctypes.data ),  len(ar) )
+print "FFI", s , (time.clock()-start)/N
+
+N=10
+start = time.clock()
+for i in range(N):
+    sn = ar.sum()
+print "Numpy",sn, (time.clock() - start)/N
+#raw_input()
+