Minor changes, mostly docs

cgt/__init__.py

@@ -1,7 +1,7 @@
 from .api import *
 from .display import print_tree, print_expr, print_text, as_dot
 from .compilation import function, numeric_eval, profiler
-from .core import grad, get_config, update_config, simplify, reset_config, Device, scoped_update_config, infer_shape
+from .core import grad, get_config, update_config, simplify, reset_config, Device, scoped_update_config, infer_shape, count_nodes
 from .ez import EasyCustomOp
 try: 
     import cycgt

cgt/api.py

@@ -324,6 +324,11 @@ def getitem_nonfancy(arr, slis):
             step = (1 if sli.step is None else sli.step)
             if (isinstance(stop, int) and (stop < 0)):
                 stop = size(arr, ax) - stop
+            if isinstance(step, int):
+                assert step != 0
+                if step < 0:
+                    raise NotImplementedError("negative `step parameter is not implemented. use flip(x,0) instead of x[::-1]")
+
             out = core.Result(core.GetSli(ax), [out, start, stop, step])
         ax += 1
     if all(((x == 'k') for x in shapedesc)):
@@ -441,7 +446,7 @@ def repeat(x, repeats, axis):
     """
     Like numpy.repeat
     """
-    return core.Result(core.Repeat([axis]), [x, constant(repeats)])
+    return core.Result(core.Repeat([axis]), [x, core.as_node(repeats)])
 
 def reshape(x, shp):
     """

cgt/compilation.py

@@ -1,6 +1,6 @@
 from . import core, utils
 import cgt
-import ctypes, os.path as osp, hashlib, numpy as np, sys, subprocess, string, os, time, traceback
+import ctypes, os.path as osp, hashlib, numpy as np, sys, subprocess, string, os, time, traceback, cPickle
 from collections import defaultdict, namedtuple
 from StringIO import StringIO
 import logging
@@ -38,10 +38,16 @@ def _function_listout(inputs, outputs, dbg = None, updates=None, givens=None):
 # Execution
 # ================================================================
 
+def python_only():
+    return not hasattr(cgt,"cycgt")
+
 def determine_devices(nodes_sorted, updatetarg2src):
     # Op definitions (available impls, inplace-ness, etc) define constraints
     # on possible devices for a node
 
+    if python_only():
+        return {node:Device() for node in nodes_sorted}
+
     # (1) Get available devices for nodes, determined by which impls are available and node types
     compile_info = get_compile_info()
 
@@ -264,7 +270,6 @@ def get_callable(op, input_types, devtype, prefer_python=False):
             else:
                 raise RuntimeError("Tried to put Op %s on the GPU but I only have a python impl :("%op)
 
-
 def get_native_callable(op, input_types, devtype):
     nci = op.get_native_compile_info(input_types, devtype)
     nci.op_str = str(op)
@@ -711,6 +716,9 @@ def call_and_print(cmd):
     ctypes.c_float : "float"
 }
 
+
+_struct_cache = {} # because creating ctypes.Structure class is slow for some reason
+
 def _build_closure(triples):
     if triples is None:
         return ctypes.c_void_p(0)
@@ -719,8 +727,13 @@ def _build_closure(triples):
     for (fieldname,fieldtype,val) in triples:
         vals.append(val)
         fields.append((fieldname,fieldtype))
-    class S(ctypes.Structure):
-        _fields_ = fields
+    try:
+        key = cPickle.dumps(fields)
+        S = _struct_cache[key]
+    except KeyError:
+        class S(ctypes.Structure):
+            _fields_ = fields
+        _struct_cache[key] = S
     closure = S(*vals)    
     return closure
 

cgt/core.py

@@ -2666,6 +2666,9 @@ def topsorted(outputs):
     return out
 
 def count_nodes(outputs):
+    """
+    Given a list of output nodes, compute the number of ancestors
+    """
     if isinstance(outputs, Node): outputs = [outputs]
     return len(list(topsorted(outputs)))