Fix #243, let output SPs read a global memory address space.

Some cleanup to follow.

Author: Feras A Saad

src/utils/general.py

@@ -128,6 +128,14 @@ def logsumexp(array):
     # so a - m <= 0; hence exp(a - m) is guaranteed not to overflow.
     return m + math.log(sum(math.exp(a - m) for a in array))
 
+def relerr(expected, actual):
+    """Relative error between `expected` and `actual`: ``abs((a - e)/e)``."""
+    return abs((actual - expected)/expected)
+
+def abserr(expected, actual):
+    """Relative error between `expected` and `actual`: ``abs((a - e))``."""
+    return abs((actual - expected))
+
 def logmeanexp(array):
     # https://github.com/probcomp/bayeslite/blob/master/src/math_util.py
     inf = float('inf')

src/venturescript/helpers.py

@@ -0,0 +1,62 @@
+# -*- coding: utf-8 -*-
+
+#   Copyright (c) 2010-2016, MIT Probabilistic Computing Project
+#
+#   Licensed under the Apache License, Version 2.0 (the 'License');
+#   you may not use this file except in compliance with the License.
+#   You may obtain a copy of the License at
+#
+#       http://www.apache.org/licenses/LICENSE-2.0
+#
+#   Unless required by applicable law or agreed to in writing, software
+#   distributed under the License is distributed on an 'AS IS' BASIS,
+#   WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+#   See the License for the specific language governing permissions and
+#   limitations under the License.
+
+import venture.lite.types as vt
+import venture.lite.value as vv
+
+from venture.lite.sp_help import deterministic_typed
+
+from venture.exception import VentureException
+
+# XXX Mutators generally do not exist in Venture.
+def dict_set(d, k, v):
+    assert isinstance(d, vv.VentureDict)
+    d.dict[k] = v
+
+def dict_pop(d, k):
+    assert isinstance(d, vv.VentureDict)
+    return d.dict.pop(k)
+
+def dict_pop2(d, k):
+    assert isinstance(d, vv.VentureDict)
+    return dict_pop(d, k) if k in d.dict else vv.VentureNil()
+
+def check_unbound_sp(ripl, name):
+    try:
+        ripl.sample(name)
+        return False
+    except VentureException:
+        return True
+
+def __venture_start__(ripl):
+    if check_unbound_sp(ripl, 'dict_set'):
+        ripl.bind_foreign_sp('dict_set', deterministic_typed(
+            dict_set,
+            [vt.HomogeneousMappingType(vt.AnyType('k'), vt.AnyType('v')),
+                vt.AnyType('k'), vt.AnyType('v')],
+            vt.NilType()))
+    if check_unbound_sp(ripl, 'dict_pop'):
+        ripl.bind_foreign_sp('dict_pop', deterministic_typed(
+            dict_pop,
+            [vt.HomogeneousMappingType(vt.AnyType('k'), vt.AnyType('v')),
+                vt.AnyType('k')],
+            vt.AnyType('v')))
+    if check_unbound_sp(ripl, 'dict_pop2'):
+        ripl.bind_foreign_sp('dict_pop2', deterministic_typed(
+            dict_pop2,
+            [vt.HomogeneousMappingType(vt.AnyType('k'), vt.AnyType('v')),
+                vt.AnyType('k')],
+            vt.AnyType('v')))