fix bugs in the GIF model

Author: c-xy17

brainpy/dyn/neurons/reduced_models.py

@@ -714,7 +714,7 @@ def __init__(self, size, V_rest=-70., V_reset=-70., V_th_inf=-50., V_th_reset=-6
     self.I1 = bm.Variable(bm.zeros(self.num))
     self.I2 = bm.Variable(bm.zeros(self.num))
     self.V_th = bm.Variable(bm.ones(self.num) * -50.)
-    self.V = bm.Variable(bm.zeros(self.num))
+    self.V = bm.Variable(bm.zeros(self.num) - 70.)
     self.input = bm.Variable(bm.zeros(self.num))
     self.spike = bm.Variable(bm.zeros(self.num, dtype=bool))
     self.t_last_spike = bm.Variable(bm.ones(self.num) * -1e7)