add comments

colossalai/autochunk/autochunk_codegen.py

-from typing import Any, Callable, Dict, Iterable, List, Tuple
+from typing import Any, Dict, Iterable, List, Tuple
 
 import torch
 from torch.fx.graph import (
@@ -128,37 +128,42 @@ def _replace_input_var(chunk_inputs, region_idx, chunk_inputs_dim, node_idx, bod
 
 
 def emit_code_with_chunk(
-    body,
-    nodes,
+    body: List[str],
+    nodes: Iterable[Node],
     emit_node_func,
     delete_unused_value_func,
     search_chunk: SearchChunk,
-    chunk_infos,
+    chunk_infos: List,
 ):
-    """Emit code with nested activation checkpoint
-    When we detect some of the node.activation_checkpoint is a List, we will use
-    this function to emit the activation checkpoint codes.
+    """
+    Emit code with chunk according to chunk_infos.
+    
+    It will generate a for loop in chunk regions, and replace inputs 
+        and outputs of regions with chunked variables.
 
     Args:
         body: forward code
-        ckpt_func: checkpoint functions code
         nodes: graph.nodes
         emit_node_func: function to emit node
         delete_unused_value_func: function to remove the unused value
+        search_chunk: the class to search all chunks
+        chunk_infos: store all information about all chunks.
     """
     node_list = list(nodes)
 
-    chunk_regions = [i["region"] for i in chunk_infos]
-    chunk_starts = [i[0] for i in chunk_regions]
-    chunk_ends = [i[1] for i in chunk_regions]
+    # chunk region
+    chunk_starts = [i["region"][0] for i in chunk_infos]
+    chunk_ends = [i["region"][1] for i in chunk_infos]
 
-    chunk_inputs = [i["inputs"] for i in chunk_infos]
-    chunk_inputs_non_chunk = [i["inputs_non_chunk"] for i in chunk_infos]
-    chunk_inputs_dim = [i["inputs_dim"] for i in chunk_infos]
+    # chunk inputs
+    chunk_inputs = [i["inputs"] for i in chunk_infos] # input with chunk
+    chunk_inputs_non_chunk = [i["inputs_non_chunk"] for i in chunk_infos] # input without chunk
+    chunk_inputs_dim = [i["inputs_dim"] for i in chunk_infos] # input chunk dim
     chunk_inputs_names = [j.name for i in chunk_inputs for j in i] + [
         j.name for i in chunk_inputs_non_chunk for j in i
     ]
 
+    # chunk outputs
     chunk_outputs = [i["outputs"][0] for i in chunk_infos]
     chunk_outputs_dim = [i["outputs_dim"] for i in chunk_infos]
 
@@ -170,6 +175,7 @@ def emit_code_with_chunk(
     while node_idx < len(node_list):
         node = node_list[node_idx]
 
+        # if is chunk start, generate for loop start
         if node_idx in chunk_starts:
             within_chunk_region = True
             region_idx = chunk_starts.index(node_idx)
@@ -203,6 +209,7 @@ def emit_code_with_chunk(
             if node_idx not in chunk_inputs:
                 delete_unused_value_func(node, body, chunk_inputs_names)
 
+        # generate chunk region end
         if node_idx in chunk_ends:
             body.append(
                 _gen_loop_end(

tests/test_autochunk/test_autochunk_codegen.py

@@ -115,4 +115,4 @@ def test_autochunk_codegen(msa_len, pair_len, max_memory):
 
 
 if __name__ == "__main__":
-    _test_autochunk_codegen(0, 32, 64, None)
+    _test_autochunk_codegen(0, 32, 64, 25)