Fix split's last factor issue (apache#4044)

python/tvm/autotvm/task/space.py

@@ -226,7 +226,8 @@ def __init__(self, axes, policy, **kwargs):
     def _generate_space(self, now, tmp_stack, enforce_no_tail=False):
         """Generate space by DFS"""
         if now == self.num_output - 1:
-            if not enforce_no_tail or self.product % np.prod(tmp_stack, dtype=np.int64) == 0:
+            prod = np.prod(tmp_stack, dtype=np.int64)
+            if self.product % prod == 0 or (not enforce_no_tail and prod < self.product):
                 self.entities.append(SplitEntity([-1] + tmp_stack[::-1]))
         else:
             for factor in self.factors:

tests/python/unittest/test_autotvm_space.py

@@ -42,6 +42,26 @@ def test_split():
     assert len(cfg) == 64
     assert len(cfg.space_map['tile_y']) == 8
 
+    # test policy
+    cfg = ConfigSpace()
+    cfg.define_split('tile_x', cfg.axis(256), policy='factors', num_outputs=3)
+    assert len(cfg.space_map['tile_x']) == 45
+
+    cfg.define_split('tile_y', cfg.axis(256), policy='power2', num_outputs=3)
+    assert len(cfg.space_map['tile_y']) == 45
+
+    cfg.define_split('tile_z', cfg.axis(256), policy='verbose', num_outputs=3)
+    assert len(cfg.space_map['tile_z']) == 45
+
+    cfg.define_split('tile_a', cfg.axis(224), policy='factors', num_outputs=3)
+    assert len(cfg.space_map['tile_a']) == 63
+
+    cfg.define_split('tile_b', cfg.axis(224), policy='power2', num_outputs=3)
+    assert len(cfg.space_map['tile_b']) == 36
+
+    cfg.define_split('tile_c', cfg.axis(224), policy='verbose', num_outputs=3)
+    assert len(cfg.space_map['tile_c']) == 84
+
     # test fallback
     cfg = FallbackConfigEntity()
     cfg.define_split('tile_n', cfg.axis(128), num_outputs=3)