RecomputeOptimizer: rm unused ckpt and sort ckpt (#20108)

* rm unused ckpt and sort ckpt

* use max op idx to sort, test=develop

* remove unsed code,test=develop

* add testcase, test_develop

* modify test case, test=develop

python/paddle/fluid/backward.py

@@ -19,14 +19,19 @@ from . import core
 import collections
 import copy
 import six
+import logging
 from .. import compat as cpt
 from . import unique_name
+from . import log_helper
 
 __all__ = [
     'append_backward',
     'gradients',
 ]
 
+_logger = log_helper.get_logger(
+    __name__, logging.INFO, fmt='%(asctime)s-%(levelname)s: %(message)s')
+
 
 class ProgramStats(object):
     def __init__(self, block, ops):
@@ -38,7 +43,7 @@ class ProgramStats(object):
     def get_input_nodes(self):
         input_names = []
         for name in self.var_op_deps:
-            if len(self.var_op_deps[name]["var_as_output_ops"]) <= 0 and \
+            if len(self.var_op_deps[name]["var_as_output_ops"]) == 0 and \
                len(self.var_op_deps[name]["var_as_input_ops"]) > 0:
                 if self.block.var(name).persistable:
                     continue
@@ -115,6 +120,22 @@ class ProgramStats(object):
             for op_idx in self.op_deps[i]["in_ops"]:
                 self.op_deps[op_idx]["out_ops"].extend([i])
 
+    def sort_checkpoints(self, checkpoints_name):
+        sorted_checkpoints = []
+        for name in checkpoints_name:
+            if name not in self.var_op_deps:
+                _logger.debug(
+                    "Recompute Optimizer: deleted %s from checkpoints, because it is not used in paddle program."
+                    % name)
+            elif self.var_op_deps[name]["var_as_output_ops"] == []:
+                # input nodes
+                sorted_checkpoints.append((name, -1))
+            else:
+                sorted_checkpoints.append(
+                    (name, max(self.var_op_deps[name]["var_as_output_ops"])))
+        sorted_checkpoints = sorted(sorted_checkpoints, key=lambda x: x[1])
+        return [x[0] for x in sorted_checkpoints]
+
 
 def _pretty_op_desc_(op_desc, prefix):
     out_s = "%s\tname:[%s]\n%s    \tinputs:[%s]\n%s    \toutputs:[%s]" % \
@@ -584,15 +605,17 @@ def _append_backward_ops_with_checkpoints_(
     """
 
     checkpoints_name = [x.name for x in checkpoints]
+    checkpoints_name = list(set(checkpoints_name))
     local_block = block.program._create_block()
     buffer_block = block.program._create_block()
 
     # 1) find ops between checkpoints, i.e. recompute_segments
     program_stat = ProgramStats(block, ops)
     program_stat.build_stats()
+    checkpoints_name = program_stat.sort_checkpoints(checkpoints_name)
     segments = []
 
-    if len(checkpoints) == 1:
+    if len(checkpoints_name) == 1:
         # only one checkpoint
         max_op_idx = -1
         var_group = [checkpoints_name[0]]
@@ -616,8 +639,6 @@ def _append_backward_ops_with_checkpoints_(
                 segments.append([min_idx, max_idx + 1])
             start_idx += 1
 
-    checkpoints_name = list(set(checkpoints_name))
-
     if segments != [] and segments[0][0] != 0:
         recompute_segments = [[0, segments[0][0]]] + segments
     else:
@@ -635,10 +656,6 @@ def _append_backward_ops_with_checkpoints_(
     vars_should_be_hold.extend(program_stat.get_input_nodes())
     vars_should_be_hold = list(set(vars_should_be_hold))
 
-    # find variables that can not be deleted
-    grad_should_be_hold = [x + "@GRAD" for x in vars_should_be_hold]
-    vars_should_be_hold.extend(grad_should_be_hold)
-
     # 3) go through each recompute_segments, add backward ops with forward recomputation
     grad_op_descs = []
     var_name_dict = {}

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

@@ -614,7 +614,7 @@ class TestLookaheadOptimizer(unittest.TestCase):
 
 
 class TestRecomputeOptimizer(unittest.TestCase):
-    def net(self):
+    def net(self, return_input=False):
         program = framework.Program()
         block = program.global_block()
         mul_x = block.create_parameter(
@@ -652,6 +652,8 @@ class TestRecomputeOptimizer(unittest.TestCase):
         block.append_op(
             type="mean", inputs={"X": b2_out}, outputs={"Out": mean_out})
 
+        if return_input == True:
+            return mul_x, mul_out, b1_out, b2_out, mean_out
         return mul_out, b1_out, b2_out, mean_out
 
     def test_no_checkpoint(self):
@@ -723,6 +725,42 @@ class TestRecomputeOptimizer(unittest.TestCase):
             "elementwise_add_grad", "mul_grad", "sgd", "sgd", "sgd"
         ])
 
+    def test_out_of_order_checkpoint(self):
+        mul_out, b1_out, b2_out, mean_out = self.net()
+        self.assertEqual(len(mean_out.block.ops), 4)
+        self.assertEqual([op.type for op in mean_out.block.ops],
+                         ["mul", "elementwise_add", "elementwise_add", "mean"])
+        sgd_optimizer = optimizer.SGD(learning_rate=1.0)
+        recompute_optimizer = optimizer.RecomputeOptimizer(sgd_optimizer)
+        recompute_optimizer._set_checkpoints([b2_out, mul_out])
+        opts, params_grads = recompute_optimizer.minimize(mean_out)
+
+        self.assertEqual(len(mean_out.block.ops), 13)
+        self.assertEqual([op.type for op in mean_out.block.ops], [
+            "mul", "elementwise_add", "elementwise_add", "mean",
+            "fill_constant", "mean_grad", "elementwise_add",
+            "elementwise_add_grad", "elementwise_add_grad", "mul_grad", "sgd",
+            "sgd", "sgd"
+        ])
+
+    def test_input_as_checkpoints(self):
+        mul_x, mul_out, b1_out, b2_out, mean_out = self.net(return_input=True)
+        self.assertEqual(len(mean_out.block.ops), 4)
+        self.assertEqual([op.type for op in mean_out.block.ops],
+                         ["mul", "elementwise_add", "elementwise_add", "mean"])
+        sgd_optimizer = optimizer.SGD(learning_rate=1.0)
+        recompute_optimizer = optimizer.RecomputeOptimizer(sgd_optimizer)
+        recompute_optimizer._set_checkpoints([mul_x, b2_out])
+        opts, params_grads = recompute_optimizer.minimize(mean_out)
+
+        self.assertEqual(len(mean_out.block.ops), 14)
+        self.assertEqual([op.type for op in mean_out.block.ops], [
+            "mul", "elementwise_add", "elementwise_add", "mean",
+            "fill_constant", "mean_grad", "mul", "elementwise_add",
+            "elementwise_add_grad", "elementwise_add_grad", "mul_grad", "sgd",
+            "sgd", "sgd"
+        ])
+
     def test_apply_gradients(self):
         mul_out, b1_out, b2_out, mean_out = self.net()
         sgd_optimizer = optimizer.SGD(learning_rate=1.0)