Fix problem use recompute and dgc same time (#23010)

python/paddle/fluid/optimizer.py

@@ -3926,6 +3926,9 @@ class RecomputeOptimizer(Optimizer):
                 parameter_list,
                 no_grad_set,
                 checkpoints=self._checkpoints)
+            # Note: since we can't use all_reduce_op now,
+            #  dgc_op should be the last op of one grad.
+            self._optimizer._append_dgc_ops(params_grads)
         return params_grads
 
     def apply_optimize(self, loss, startup_program, params_grads):

python/paddle/fluid/tests/unittests/test_dgc_optimizer.py

@@ -35,7 +35,8 @@ class TestDGCMomentumOptimizer(unittest.TestCase):
     def check_dgc_momentum_optimizer(self,
                                      dims=[5, 10, 8],
                                      name="momentum",
-                                     regularization=None):
+                                     regularization=None,
+                                     use_recompute=False):
         init_program = framework.Program()
         program = framework.Program()
         block = program.global_block()
@@ -72,6 +73,13 @@ class TestDGCMomentumOptimizer(unittest.TestCase):
             local_grad_clip_norm=1.0,
             num_trainers=2,
             regularization=regularization)
+
+        if use_recompute:
+            dgc_momentum_optimizer = optimizer.RecomputeOptimizer(
+                dgc_momentum_optimizer)
+            dgc_momentum_optimizer.get_accumulators = dgc_momentum_optimizer._optimizer.get_accumulators
+            dgc_momentum_optimizer.get_velocity_str = dgc_momentum_optimizer._optimizer.get_velocity_str
+
         mean_out = block.create_var(
             dtype="float32", shape=[1], lod_level=0, name="mean.out")
         block.append_op(
@@ -112,8 +120,9 @@ class TestDGCMomentumOptimizer(unittest.TestCase):
                 self.assertAlmostEqual(op.attr('regular_coeff'), coeff)
                 print("dgc regular_coeff=" + str(coeff))
 
-        with open("test_dgc_optimizer_" + name + ".log", "w") as f:
-            program_to_code(program, fout=f)
+        # for local test debug
+        #with open("test_dgc_optimizer_" + name + str(use_recompute) + ".log", "w") as f:
+        #    program_to_code(program, fout=f)
 
     def test_momentum_without_dgc(self):
         self.check_dgc_momentum_optimizer(
@@ -130,6 +139,14 @@ class TestDGCMomentumOptimizer(unittest.TestCase):
         self.check_dgc_momentum_optimizer(
             dims=[16, 1024, 8], name="dgc_momentum")
 
+    def test_momentum_with_dgc_recompute(self):
+        # 16 * 1024 = 16384, use dgc momentum
+        self.check_dgc_momentum_optimizer(
+            dims=[16, 1024, 8],
+            name="dgc_momentum",
+            regularization=regularizer.L2Decay(1e-4),
+            use_recompute=True)
+
 
 if __name__ == '__main__':
     unittest.main()