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@fzyzcjy fzyzcjy commented Jun 12, 2025

Motivation

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Summary of Changes

Hello @fzyzcjy, I'm Gemini Code Assist1! I'm currently reviewing this pull request and will post my feedback shortly. In the meantime, here's a summary to help you and other reviewers quickly get up to speed!

This pull request adds a minor utility to the eplb_simulator package. The main purpose is to provide a convenient way to load and process data generated by the ExpertDistributionRecorder, enabling easier analysis of expert distribution patterns recorded during model execution.

Highlights

  • New Utility Module: Introduced a new module sglang.srt.eplb_simulator.reader to provide utilities for reading recorded expert distribution data.
  • Data Reading Function: Added the read_mode_per_pass function within the new reader module to load and aggregate expert distribution data saved in .pt files, specifically designed for data recorded in 'per_pass' mode.
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Code Review

The pull request introduces read_mode_per_pass in reader.py to process output from ExpertDistributionRecorder in per_pass mode. It reads .pt files, aggregates global_physical_count data, and returns it with metadata.

The review focuses on robustness, correctness (deterministic processing, handling no input files), efficiency (memory usage), and code clarity (removing debug prints).


# gpc := global_physical_count
gpc_of_forward_pass_and_rank = defaultdict(lambda: defaultdict())
for path in tqdm(list(dir_data.glob("*.pt"))):
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high

Loading all file paths into memory at once with list(dir_data.glob("*.pt")) can be memory-intensive if dir_data contains many files. Also, the iteration order from dir_data.glob("*.pt") is not guaranteed, which affects last_physical_to_logical_map.

If a specific last_physical_to_logical_map is critical, sort the paths explicitly: file_paths = sorted(list(dir_data.glob("*.pt"))). If any last_physical_to_logical_map is acceptable, iterate directly over the generator dir_data.glob("*.pt") for better memory efficiency. Clarify the intended behavior for last_physical_to_logical_map with a comment.

# Option 1: If a specific order is needed:
# file_paths_to_process = sorted(list(dir_data.glob("*.pt")))
# Option 2: If order doesn't matter and memory efficiency is prioritized:
file_paths_to_process = dir_data.glob("*.pt")
for path in tqdm(file_paths_to_process):

gpc_of_forward_pass_and_rank = defaultdict(lambda: defaultdict())
for path in tqdm(list(dir_data.glob("*.pt"))):
data_pack = torch.load(path, weights_only=True)
last_physical_to_logical_map = data_pack["last_physical_to_logical_map"]
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high

The code doesn't handle the case where dir_data.glob("*.pt") yields no files. last_physical_to_logical_map (line 23) would not be assigned, potentially leading to a NameError on line 49. items (line 37) would remain empty, and torch.stack(items) (line 44) would raise an error.

Initialize last_physical_to_logical_map to a default value (e.g., None) before the loop and check if items is empty before calling torch.stack. If no files are processed, return default/empty structures or raise a FileNotFoundError.

]

forward_pass_ids = sorted(gpc_of_forward_pass_and_rank.keys())
print(f"Make {forward_pass_ids=} into array")
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medium

This print statement is for debugging. Remove or replace it with a proper logging mechanism before merging.

# Consider using logging:
# import logging
# logger = logging.getLogger(__name__)
# logger.debug(f"Make {forward_pass_ids=} into array")

items.append(gpc_of_rank_tensor)

gpc_of_forward_pass = torch.stack(items)
print(f"{gpc_of_forward_pass.shape=}")
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medium

This print statement is also for debugging. Remove it or convert it to a log message.

# Consider using logging:
# logger.debug(f"{gpc_of_forward_pass.shape=}")

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fzyzcjy commented Jun 12, 2025

can ignore ci since this adds a new file and will not affect any existing things, and I have tested that file locally

@zhyncs zhyncs merged commit b02df20 into sgl-project:main Jun 12, 2025
88 of 98 checks passed
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2 participants