fix bug in crossover: the child from two normal networks should always be normal.

tensorneat/algorithm/neat/ga/crossover/default.py

@@ -2,6 +2,7 @@ import jax, jax.numpy as jnp
 
 from .base import BaseCrossover
 
+
 class DefaultCrossover(BaseCrossover):
 
     def __call__(self, randkey, genome, nodes1, conns1, nodes2, conns2):
@@ -14,17 +15,19 @@ class DefaultCrossover(BaseCrossover):
         # crossover nodes
         keys1, keys2 = nodes1[:, 0], nodes2[:, 0]
         # make homologous genes align in nodes2 align with nodes1
-        nodes2 = self.align_array(keys1, keys2, nodes2, False)
+        nodes2 = self.align_array(keys1, keys2, nodes2, is_conn=False)
 
         # For not homologous genes, use the value of nodes1(winner)
         # For homologous genes, use the crossover result between nodes1 and nodes2
-        new_nodes = jnp.where(jnp.isnan(nodes1) | jnp.isnan(nodes2), nodes1, self.crossover_gene(randkey_1, nodes1, nodes2))
+        new_nodes = jnp.where(jnp.isnan(nodes1) | jnp.isnan(nodes2), nodes1,
+                              self.crossover_gene(randkey_1, nodes1, nodes2, is_conn=False))
 
         # crossover connections
         con_keys1, con_keys2 = conns1[:, :2], conns2[:, :2]
-        conns2 = self.align_array(con_keys1, con_keys2, conns2, True)
+        conns2 = self.align_array(con_keys1, con_keys2, conns2, is_conn=True)
 
-        new_conns = jnp.where(jnp.isnan(conns1) | jnp.isnan(conns2), conns1, self.crossover_gene(randkey_2, conns1, conns2))
+        new_conns = jnp.where(jnp.isnan(conns1) | jnp.isnan(conns2), conns1,
+                              self.crossover_gene(randkey_2, conns1, conns2, is_conn=True))
 
         return new_nodes, new_conns
 
@@ -54,14 +57,14 @@ class DefaultCrossover(BaseCrossover):
 
         return refactor_ar2
 
-    def crossover_gene(self, rand_key, g1, g2):
-        """
-        crossover two genes
-        :param rand_key:
-        :param g1:
-        :param g2:
-        :return:
-        only gene with the same key will be crossover, thus don't need to consider change key
-        """
+    def crossover_gene(self, rand_key, g1, g2, is_conn):
         r = jax.random.uniform(rand_key, shape=g1.shape)
-        return jnp.where(r > 0.5, g1, g2)
+        new_gene = jnp.where(r > 0.5, g1, g2)
+        if is_conn:  # fix enabled
+            enabled = jnp.where(
+                g1[:, 2] + g2[:, 2] > 0,  # any of them is enabled
+                1,
+                0
+            )
+            new_gene = new_gene.at[:, 2].set(enabled)
+        return new_gene