Parallelize generateSubdivisions()

.gitignore

 .*.swp
 groupConnectivity.so
+parmap.pyc
+

Makefile

 default: groupConnectivity.so clean_obj
 
-groupConnectivity.so: groupConnectivity.pyx group-connectivity.h setup.py compileTimeOptions.h
+groupConnectivity.so: groupConnectivity.pyx group-connectivity.h setup.py compileTimeOptions.h parmap.py
 	python setup.py build_ext
 	cp build/lib*/groupConnectivity.so .
 

groupConnectivity.pyx

@@ -2,6 +2,7 @@ from libcpp.vector cimport vector
 from libcpp cimport bool
 from libcpp.utility cimport pair
 from sage.graphs.graph import Graph
+from parmap import parmap
 
 cdef extern from "group-connectivity.h" namespace "Ring":
   cdef cppclass Z4[T]:
@@ -87,12 +88,21 @@ def subdivisionIterator(G, edges = None):
     for L in subdivisionIterator(H, edges[1:]):
       yield L
 
-def generateSubdivisions(file, G, edges = None, function = lambda H: H.graph6_string()):
+
+def generateSubdivisions(file, G, edges = None,
+                         function = lambda H: H.graph6_string(),
+                         parallel = 1):
   f = open(file, 'w+')
   f.write("# Subdivisions of edges '%s' of graph '%s' (%s)\n" %
           (edges, G.graph6_string(), G))
-  for H in subdivisionIterator(G, edges):
-    f.write(function(H))
+
+  if parallel == 1:
+    iterator = map(function, subdivisionIterator(G, edges))
+  else:
+    iterator = parmap(function, subdivisionIterator(G, edges), parallel)
+
+  for line in iterator:
+    f.write(line)
     f.write("\n")
 
   f.close()

parmap.py

+# modified version of code written by klaus se from
+# http://stackoverflow.com/a/16071616
+
+import multiprocessing
+
+def fun(f, q_in, q_out):
+    while True:
+        i,x = q_in.get()
+        if i is None:
+            break
+        q_out.put((i, f(x)))
+
+def parmap(f, X, nprocs = None):
+    if nprocs is None:
+      nprocs = multiprocessing.cpu_count()
+
+    q_in   = multiprocessing.Queue(100)
+    q_out  = multiprocessing.Queue()
+
+    proc = [multiprocessing.Process(target=fun,args=(f,q_in,q_out)) for _ in range(nprocs)]
+    for p in proc:
+        p.daemon = True
+        p.start()
+
+    sent = [q_in.put((i,x)) for i,x in enumerate(X)]
+    [q_in.put((None,None)) for _ in range(nprocs)]
+
+    ret = {}
+    for _ in range(len(sent)):
+      i, val = q_out.get()
+      ret[i] = val
+
+    [ p.join() for p in proc ]
+
+    return [ ret[i] for i in range(len(sent)) ]
+