Remove identical inputs to the ifelse op (identical on both branches)

theano/lazycond.py

@@ -421,3 +421,57 @@ class CondMerge(gof.Optimizer):
                 env.replace_all_validate(pairs, reason='cond_merge')
 
 
+@gof.local_optimizer([None])
+def cond_remove_identical(node):
+    op = node.op
+
+    if not isinstance(op, IfElse):
+        return False
+    ts = node.inputs[1:][:op.n_outs]
+    fs = node.inputs[1:][op.n_outs:]
+
+    # sync outs
+    out_map = {}
+    for idx in xrange(len(node.outputs)):
+        if idx not in out_map:
+           for jdx in xrange(idx+1,len(node.outputs)):
+                if (ts[idx] == ts[jdx] and
+                    fs[idx] == fs[jdx] and
+                    jdx not in out_map):
+                    out_map[jdx] = idx
+
+    if len(out_map.keys()) == 0:
+        return False
+
+    nw_ts = []
+    nw_fs = []
+    inv_map  = {}
+    pos = 0
+    for idx in xrange(len(node.outputs)):
+        if idx not in out_map:
+            inv_map[idx] = pos
+            pos = pos + 1
+            nw_ts.append(ts[idx])
+            nw_fs.append(fs[idx])
+
+    new_ifelse = IfElse(n_outs = len(nw_ts),
+                        as_view = op.as_view,
+                        gpu = op.gpu,
+                        name = op.name)
+
+
+
+    new_ins = [node.inputs[0]] + nw_ts + nw_fs
+    new_outs = new_ifelse.make_node(*new_ins).outputs
+
+    rval = []
+    for idx in xrange(len(node.outputs)):
+        if idx in out_map.keys():
+            rval += [new_outs[inv_map[out_map[idx]]] ]
+        else:
+            rval += [new_outs[inv_map[idx]]]
+
+    return rval
+
+
+