fix collapsed RND nodes into one RND node in optimized circuits

circkit/operation.py

@@ -203,6 +203,7 @@ class Operation(metaclass=OperationMeta):
 
     PRECOMPUTABLE: bool
         Whether the operation is precomputable (given the inputs and the parameters).
+        Equivalent to whether the operation is deterministic.
 
     STR_LIMIT: int = 30
         Maximum length of the string describing parameters to keep (for
@@ -311,7 +312,7 @@ def __call__(self, *incoming, **kwargs):
                     )
                     return self._circuit.add_const(value)
 
-        if self._circuit.CACHE_NODES:
+        if self._circuit.CACHE_NODES and self.PRECOMPUTABLE:
             node_cache_key = tuple(node.id for node in incoming)
             if self.SYMMETRIC:
                 node_cache_key = tuple(sorted(node_cache_key))
@@ -328,7 +329,7 @@ def __call__(self, *incoming, **kwargs):
 
         self.after_create_node(node)
 
-        if self._circuit.CACHE_NODES:
+        if self._circuit.CACHE_NODES and self.PRECOMPUTABLE:
             self._circuit._nodes_cache[cache_key] = node
 
         return node

tests/test_random.py

@@ -0,0 +1,35 @@
+import random
+import pytest
+
+from circkit.arithmetic import ArithmeticCircuit
+from circkit.arithmetic import OptArithmeticCircuit
+
+
+class IntegerRing:
+    def __init__(self):
+        self.counter = 999
+
+    def random_element(self):
+        self.counter += 1
+        return self.counter
+
+    def __call__(self, value):
+        return int(value)
+
+
+def test_random():
+    C = ArithmeticCircuit(base_ring=IntegerRing(), name="TwoRandoms")
+    a = C.RND()()
+    b = C.RND()()
+    C.add_output(a)
+    C.add_output(b)
+    out = C.evaluate([])
+    assert out == [1000, 1001]
+
+    C = OptArithmeticCircuit(base_ring=IntegerRing(), name="TwoRandomsOpt")
+    a = C.RND()()
+    b = C.RND()()
+    C.add_output(a)
+    C.add_output(b)
+    out = C.evaluate([])
+    assert out == [1000, 1001]