added fct theano.printing.pydotprint() that write to a png file a compiled theano fct.

theano/printing.py

@@ -2,9 +2,10 @@
 """
 import gof
 from copy import copy
-import sys
-
+import sys,os
+from theano import config
 from gof import Op, Apply
+from theano.gof.python25 import any
 
 class Print(Op):
     """This identity-like Op has the side effect of printing a message followed by its inputs
@@ -299,3 +300,53 @@ pprint.assign(lambda pstate, r: hasattr(pstate, 'target') and pstate.target is n
 pp = pprint
 
 
+def pydotprint(fct, outfile=os.path.join(config.compiledir,'theano.pydotprint.png')):
+    """
+    print to a file in png format the graph of op of a compile theano fct.
+
+    :param fct: the theano fct returned by theano.function.
+    :param outfile: the output file where to put the graph.
+
+    In the graph, box are an Apply Node(the execution of an op) and elipse are variable.
+    If variable have name they are used as the text(if multiple var have the same name, they will be merged in the graph). Otherwise, if a constant, we print the value and finaly we print the type + an uniq number to don't have multiple var merged.
+    We print the op of the apply in the Apply box with a number that represent the toposort order of application of those Apply.
+    """
+    import pydot as pd
+
+    g=pd.Dot()
+    def var_name(var):
+        if var.name is not None:
+            varstr = var.name
+        elif isinstance(var,gof.Constant):
+            varstr = str(var.data)
+        else:
+            #a var id is needed as otherwise var with the same type will be merged in the graph.
+            varstr = str(var.type)+' '+str(id(var))
+        return varstr
+
+    for node_idx,node in enumerate(fct.maker.env.toposort()):
+        astr=str(node.op).replace(':','_')+'    '+str(node_idx)
+
+        g.add_node(pd.Node(astr,shape='box'))
+
+        for var in node.inputs:
+            varstr=var_name(var)
+            if var.owner is None:
+                g.add_node(pd.Node(varstr,color='green'))
+            g.add_edge(pd.Edge(varstr,astr))
+
+        for var in node.outputs:
+            varstr=var_name(var)
+
+            g.add_edge(pd.Edge(astr,varstr))
+            if any([x[0]=='output' for x in var.env.clients(var)]):
+        	g.add_node(pd.Node(varstr,color='blue'))
+
+    g.write_png(outfile, prog='dot')
+
+    print 'The output file is available at',outfile
+    #from matplotlib import pyplot
+    #image=pyplot.imread(outfile)
+    #pyplot.imshow(image)
+    #import pdb;pdb.set_trace()
+