[autoparallel] memory estimation for shape consistency (#2144)

* [fx] metainfo class for auto parallel

* [fx] add unit test for linear metainfo

* [fx] fix bwd param for linear

* [fx] modify unit test

* [fx] modify unit test

* [fx] modify import

* [fx] modify import

* [fx] modify import

* [fx] move meta profiler to auto parallel

* [fx] add conv metainfo class

* [fx] restore profiler

* [fx] restore meta profiler

* [autoparallel] modify unit test

* [fx] modify unit test

* [autoparallel] add batchnorm metainfo class

* [autoparallel] fix batchnorm unit test function declaration

* [fx] restore profiler

* [fx] add relu metainfo class

* [fx] restore profiler

* [autoparallel] modify metainfo input

* [autoparallel] add pooling metainfo

* [autoparallel] add F.linear metainfo generator

* [autoparallel] add binary elementwise metainfo

* [fx] recover profiler

* [autoparallel] fix forward memory calculation

* [autoparallel] modify constants.py

* [autoparallel] remove redundant print

* [autoparallel] add F.conv metainfo

* [autoparallel] linear fix

* [autoparallel] memory estimation for communication actions

* [autoparallel] fix docstring

* [autoparallel] fix variables name

Author: Cypher30

colossalai/auto_parallel/tensor_shard/sharding_strategy.py

@@ -6,7 +6,7 @@
 import torch
 from torch.fx.node import Node
 
-from colossalai.tensor.shape_consistency import CommSpec
+from colossalai.tensor.comm_spec import CommSpec
 from colossalai.tensor.sharding_spec import ShardingSpec
 
 from .constants import (

colossalai/tensor/shape_consistency.py

@@ -3,8 +3,10 @@
 from dataclasses import dataclass
 from typing import Dict, List, Tuple
 
+import numpy as np
 import torch
 
+from colossalai.auto_parallel.tensor_shard.sharding_strategy import MemoryCost, TrainCycleItem
 from colossalai.context.singleton_meta import SingletonMeta
 from colossalai.tensor.sharding_spec import ShardingSpec, ShardingSpecException
 from colossalai.tensor.utils import all_gather_simulator, all_to_all_simulator, mix_gather_simulator, shard_simulator
@@ -403,6 +405,158 @@ def get_all_one_step_transform_spec(self, source_spec: ShardingSpec, orig_cost_d
         valid_spec_dict.update(self.get_all_shard_spec(source_spec, orig_cost_dict))
         return valid_spec_dict
 
+    def mem_cost(self, comm_action_sequence: List[CommSpec]) -> TrainCycleItem:
+        """memory cost of the communication action sequence
+        TODO: Currently we just consider tensor numel in the shape consistency manger,
+        as the manager itself doesn't have the access to tensor dtype, we need to take
+        it into consideration in memory estimation.
+
+        Args:
+            comm_action_sequence (List[CommSpec]): list of communication actions
+
+        Returns:
+            TrainCycleItem: memory (numel) cost of such comm_action_sequence
+        """
+
+        def compute_shape(sharding_spec: ShardingSpec):
+            shape = sharding_spec.entire_shape
+            for dim, shard in sharding_spec.dim_partition_dict.items():
+                shape[dim] = shape[dim] // len(shard)
+            return shape
+
+        def gather_analysis(comm_spec: CommSpec, discard_input: bool, alloc_numel: int, peak_numel: int):
+            """analyze all_gather memory footprint
+            all_gather will allocate memory for the output tensor, and there will be temp memory for
+            all_gather operation, which is twice the size of output tensor
+
+            Args:
+                comm_spec (CommSpec): input CommSpec
+                discard_input (bool): whether to discard the input tensor
+                alloc_numel (int): current allocated numel
+                peak_numel (int): current peak numel
+            """
+            input_shape = compute_shape(comm_spec.sharding_spec)
+            input_numel = np.prod(input_shape)
+            output_numel = input_numel * comm_spec.device_mesh.mesh_shape[comm_spec.logical_process_axis]
+            peak_numel = max(peak_numel, alloc_numel + output_numel * 2)
+            alloc_numel += output_numel
+            if discard_input:
+                alloc_numel -= input_numel
+
+        def split_analysis(comm_spec: CommSpec, discard_input: bool, alloc_numel: int, peak_numel: int):
+            """analyze split memory footprint
+            split will allocate memory for the output tensor if we don't apply shard on the first dimension of
+            the input tensor. If we apply shard on the first dimension, the `torch.tensor.contiguous()` will not
+            generate new tensor in this case, so no memory will be allocated.
+
+            Args:
+                comm_spec (CommSpec): input CommSpec
+                discard_input (bool): whether to discard the input tensor
+                alloc_numel (int): current allocated numel
+                peak_numel (int): current peak numel
+            """
+            shard_dim = comm_spec.shard_dim
+            if shard_dim != 0:
+                # if we don't shard the tensor on the first dimension, the split action will
+                # generate a new tensor
+                input_shape = compute_shape(comm_spec.sharding_spec)
+                input_numel = np.prod(input_shape)
+                output_numel = input_numel // comm_spec.device_mesh.mesh_shape[comm_spec.logical_process_axes]
+                alloc_numel += output_numel
+                peak_numel = max(peak_numel, alloc_numel)
+                if discard_input:
+                    alloc_numel -= input_numel
+            else:
+                # if we shard the tensor on the first dimension, the split action will not generate
+                # a new tensor, and as it will preserve a reference to the input tensor, we could
+                # override the discard_input option here
+                # NOTE: this special case might fail in some weird cases, e.g. if we have three split
+                # actions in the comm actions sequence, the first split action operate on the second dimension,
+                # the second split action operate on the first dimension, and the third split action operate, again,
+                # on the second dimension. Therefore, after the first two actions in the sequence, we will allocate
+                # memory the same size as the output of first split action. However, the third split action will discard
+                # the input tensor, and it actually should discard the tensor generated by the first split action, so in
+                # the current memory estimation framework, we will overestimate the memory usage. But the above case is
+                # kind of weird, and I think we could ignore it for now.
+                pass
+
+        def reduce_analysis(comm_spec: CommSpec, discard_input: bool, alloc_numel: int, peak_numel: int):
+            """
+            a dummy function for reduce memory footprint analysis, as the reduce action doesn't allocate extra memory
+            """
+            pass
+
+        def all2all_analysis(comm_spec: CommSpec, discard_input: bool, alloc_numel: int, peak_numel: int):
+            """analyze all_to_all memory footprint
+            all_to_all will allocate memory for the output tensor, and temp memory of all_to_all action
+            is twice the size of output tensor if we shard input tensor on the first dimension, otherwise
+            the temp memory is three times the size of output tensor
+
+            Args:
+                comm_spec (CommSpec): input CommSpec
+                discard_input (bool): whether to discard the input tensor
+                alloc_numel (int): current allocated numel
+                peak_numel (int): current peak numel
+            """
+            input_shape = compute_shape(comm_spec.sharding_spec)
+            input_numel = np.prod(input_shape)
+            output_numel = input_numel
+            shard_dim = comm_spec.shard_dim
+            if shard_dim != 0:
+                peak_numel = max(peak_numel, alloc_numel + output_numel * 3)
+            else:
+                peak_numel = max(peak_numel, alloc_numel + output_numel * 2)
+            alloc_numel += output_numel
+            if discard_input:
+                alloc_numel -= input_numel
+
+        def identity_analysis(comm_spec: CommSpec, discard_input: bool, alloc_numel: int, peak_numel: int):
+            """
+            a dummy function for identity memory footprint analysis, as the identity action doesn't allocate extra memory
+            """
+            pass
+
+        pattern_to_func_dict = {
+            CollectiveCommPattern.GATHER_FWD_SPLIT_BWD: [gather_analysis, split_analysis],
+            CollectiveCommPattern.ALL2ALL_FWD_ALL2ALL_BWD: [all2all_analysis, all2all_analysis],
+            CollectiveCommPattern.SPLIT_FWD_GATHER_BWD: [split_analysis, gather_analysis],
+            CollectiveCommPattern.ALLREDUCE_FWD_IDENTITY_BWD: [reduce_analysis, identity_analysis],
+            CollectiveCommPattern.IDENTITY_FWD_ALLREDUCE_BWD: [identity_analysis, reduce_analysis],
+            CollectiveCommPattern.MIXGATHER_FWD_SPLIT_BWD: [],
+        }
+
+        fwd_actions = []
+        bwd_actions = []
+
+        # construct forward and backward comm actions sequence
+        for comm_spec in comm_action_sequence:
+            comm_spec: CommSpec
+            fwd_action, bwd_action = pattern_to_func_dict[comm_spec.comm_pattern]
+            fwd_actions.append(fwd_action)
+            bwd_actions.append(bwd_action)
+
+        # analyze memory footprint of forward comm actions sequence
+        fwd_alloc_numel = 0
+        fwd_peak_numel = 0
+        for idx, fwd_action, comm_spec in enumerate(zip(fwd_actions, comm_action_sequence)):
+            # the first forward comm action will not discard input
+            if idx == 0:
+                fwd_action(comm_spec, False, fwd_alloc_numel, fwd_peak_numel)
+            else:
+                fwd_action(comm_spec, True, fwd_alloc_numel, fwd_peak_numel)
+
+        # analyze memory footprint for backward comm actions sequence
+        bwd_alloc_numel = 0
+        bwd_peak_numel = 0
+        for idx, bwd_action, comm_spec in enumerate(zip(reversed(bwd_actions), reversed(comm_action_sequence))):
+            bwd_action(comm_spec, True, bwd_alloc_numel, bwd_peak_numel)
+
+        fwd_mem = MemoryCost(activation=fwd_alloc_numel, temp=fwd_peak_numel - fwd_alloc_numel)
+        bwd_mem = MemoryCost(activation=bwd_alloc_numel, temp=bwd_peak_numel - bwd_alloc_numel)
+        total_mem = MemoryCost(activation=fwd_alloc_numel + bwd_alloc_numel)
+
+        return TrainCycleItem(fwd_mem, bwd_mem, total_mem)
+
     def shape_consistency(self, source_spec: ShardingSpec,
                           target_spec: ShardingSpec) -> Tuple[List[ShardingSpec], List[CommSpec], float]:
         '''