add minimal vectorized example

capi/examples/example.c

@@ -10,7 +10,12 @@ int main() {
     const double x = 0.1, q2 = 1.65;
     for (int fl=-5; fl <=5; fl++)
         printf("flv=%d - xfx = %f\n", fl, xfxq2(fl, x, q2));
-    printf("alphas(q2=%f) = %f\n", q2, alphasq2(q2));
+
+    double q2_vectorized[] = {1.65, 10.65};
+    double* as_vectorized = alphasq2(q2_vectorized, 2);
+
+    printf("alphas(q2=%f) = %f\n", q2_vectorized[0], as_vectorized[0]);
+    printf("alphas(q2=%f) = %f\n", q2_vectorized[1], as_vectorized[1]);
 
     return 0;
 }

capi/src/pdfflow/pdfflow.h

@@ -6,4 +6,4 @@ extern void mkpdf(const char *fname, const char * dirname);
 
 extern double xfxq2(int pid, double x, double q2);
 
-extern double alphasq2(double q2);
+extern double *alphasq2(double *q2, int n);

capi/src/wrapper.py

@@ -1,6 +1,7 @@
 # This file is part of
 from cpdfflow import ffi
 from pdfflow import pflow
+import numpy as np
 
 pdf = None
 
@@ -21,7 +22,9 @@ def xfxq2(pid, x, q2):
 
 
 @ffi.def_extern()
-def alphasq2(q2):
+def alphasq2(q2, n):
     """Returns the alpha strong coupling at specific q2 value."""
     global pdf
-    return pdf.alphasQ2([q2])
+    q2_numpy = np.frombuffer(ffi.buffer(q2, n*ffi.sizeof('double')), dtype='double')
+    ret = pdf.alphasQ2(q2_numpy).numpy()
+    return ffi.cast("double*", ffi.from_buffer(ret))