[fix] fix #287

Author: chaoming0625

brainpy/dyn/base.py

@@ -182,7 +182,8 @@ def register_delay(
         elif delay.num_delay_step - 1 < max_delay_step:
           self.global_delay_data[identifier][0].reset(delay_target, max_delay_step, initial_delay_data)
     else:
-      self.global_delay_data[identifier] = (None, delay_target)
+      if identifier not in self.global_delay_data:
+        self.global_delay_data[identifier] = (None, delay_target)
     self.register_implicit_nodes(self.local_delay_vars)
     return delay_step
 

brainpy/dyn/tests/test_base.py

@@ -0,0 +1,20 @@
+# -*- coding: utf-8 -*-
+
+import unittest
+
+import brainpy as bp
+
+
+class TestDynamicalSystem(unittest.TestCase):
+  def test_delay(self):
+    A = bp.neurons.LIF(1)
+    B = bp.neurons.LIF(1)
+    C = bp.neurons.LIF(1)
+    A2B = bp.synapses.Exponential(A, B, bp.conn.All2All(), delay_step=1)
+    A2C = bp.synapses.Exponential(A, C, bp.conn.All2All(), delay_step=None)
+    net = bp.Network(A, B, C, A2B, A2C)
+
+    runner = bp.DSRunner(net,)
+    runner.run(10.)
+
+