add ARS to train/eval Minitaur

examples/pybullet/gym/pybullet_envs/ARS/utils.py

@@ -0,0 +1,28 @@
+# Code in this file is copied and adapted from
+# https://github.com/openai/evolution-strategies-starter.
+
+import numpy as np
+
+def itergroups(items, group_size):
+    assert group_size >= 1
+    group = []
+    for x in items:
+        group.append(x)
+        if len(group) == group_size:
+            yield tuple(group)
+            del group[:]
+    if group:
+        yield tuple(group)
+
+
+
+def batched_weighted_sum(weights, vecs, batch_size):
+    total = 0
+    num_items_summed = 0
+    for batch_weights, batch_vecs in zip(itergroups(weights, batch_size),
+                                         itergroups(vecs, batch_size)):
+        assert len(batch_weights) == len(batch_vecs) <= batch_size
+        total += np.dot(np.asarray(batch_weights, dtype=np.float64),
+                        np.asarray(batch_vecs, dtype=np.float64))
+        num_items_summed += len(batch_weights)
+    return total, num_items_summed