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2026-07-13 12:37:59 +08:00

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Python

"""
Downloads and evaluates MMLU in Python.
This then acts as the reference file for llm.c
https://github.com/hendrycks/test
gpt2 (124M)
- this script: 14042 acc: 0.2557 acc_norm: 0.2721
gpt2-xl (1558M)
- this script: 14042 acc: 0.2927 acc_norm: 0.3035
"""
import os
import requests
import tiktoken
import pandas as pd
from tqdm import tqdm
import torch
import torch.nn as nn
from torch.nn import functional as F
from transformers import GPT2LMHeadModel
from data_common import download_file
# -----------------------------------------------------------------------------
DATA_CACHE_DIR = os.path.join(os.path.dirname(__file__), "mmlu")
enc = tiktoken.get_encoding("gpt2")
data_url = "https://people.eecs.berkeley.edu/~hendrycks/data.tar"
def download():
"""Downloads MMLU to DATA_CACHE_DIR"""
os.makedirs(DATA_CACHE_DIR, exist_ok=True)
data_filename = os.path.join(DATA_CACHE_DIR, f"data.tar")
if not os.path.exists(data_filename):
print(f"Downloading {data_url} to {data_filename}...")
download_file(data_url, data_filename)
os.system(f"tar -xf {data_filename} -C {DATA_CACHE_DIR}") # untar
# creates a directory "data" inside it, with e.g. data/test/*csv
else:
print(f"{data_filename} already exists, skipping download...")
def iterate_examples():
# there are 14,042 examples in total in the test set
download()
test_dir = os.path.join(DATA_CACHE_DIR, "data", "test")
csv_files = [f for f in os.listdir(test_dir) if f.endswith(".csv")]
for csv_file in csv_files:
csv_path = os.path.join(test_dir, csv_file)
print(csv_path)
df = pd.read_csv(csv_path, header=None)
n = df.shape[0]
for idx in range(n):
example = {
"question": df.iloc[idx, 0],
"endings": [df.iloc[idx, 1], df.iloc[idx, 2], df.iloc[idx, 3], df.iloc[idx, 4]],
"label": df.iloc[idx, 5],
}
yield example
def render_example(example):
"""
Given the example as a dictionary, render it as three torch tensors:
- tokens (the tokens of context + completion, of size 4xN, as there are always 4 candidates)
- mask (is 1 in the region of the candidate completion, where we evaluate likelihoods)
- label (the index of the correct completion, which we hope has the highest likelihood)
"""
ctx = f"Question: {example['question']}\n\nAnswer:"
ctx_tokens = enc.encode(ctx)
tok_rows = []
mask_rows = []
for end in example["endings"]:
end_tokens = enc.encode(" " + str(end)) # note: prepending " " because GPT-2 tokenizer
tok_rows.append(ctx_tokens + end_tokens)
mask_rows.append([0]*len(ctx_tokens) + [1]*len(end_tokens))
# have to be careful during the collation because the number of tokens in each row can differ
max_len = max(len(row) for row in tok_rows)
tokens = torch.zeros((4, max_len), dtype=torch.long)
mask = torch.zeros((4, max_len), dtype=torch.long)
for i, (tok_row, mask_row) in enumerate(zip(tok_rows, mask_rows)):
tokens[i, :len(tok_row)] = torch.tensor(tok_row)
mask[i, :len(mask_row)] = torch.tensor(mask_row)
label = "ABCD".index(example["label"])
return tokens, mask, label
@torch.no_grad()
def evaluate(model_type, device):
torch.set_float32_matmul_precision('high') # use tf32
model = GPT2LMHeadModel.from_pretrained(model_type)
model.to(device)
# model = torch.compile(model)
num_correct_norm = 0
num_correct = 0
num_total = 0
for example in iterate_examples():
tokens, mask, label = render_example(example)
tokens = tokens.to(device)
mask = mask.to(device)
# get the logits
logits = model(tokens).logits
# evaluate the autoregressive loss at all positions
shift_logits = (logits[..., :-1, :]).contiguous()
shift_tokens = (tokens[..., 1:]).contiguous()
flat_shift_logits = shift_logits.view(-1, shift_logits.size(-1))
flat_shift_tokens = shift_tokens.view(-1)
shift_losses = F.cross_entropy(flat_shift_logits, flat_shift_tokens, reduction='none')
shift_losses = shift_losses.view(tokens.size(0), -1)
# now get the average loss just for the completion region (where mask == 1), in each row
shift_mask = (mask[..., 1:]).contiguous() # we must shift mask, so we start at the last prompt token
masked_shift_losses = shift_losses * shift_mask
# sum and divide by the number of 1s in the mask
sum_loss = masked_shift_losses.sum(dim=1)
avg_loss = sum_loss / shift_mask.sum(dim=1)
# now we have a loss for each of the 4 completions
# the one with the lowest loss should be the most likely
pred = sum_loss.argmin().item()
pred_norm = avg_loss.argmin().item()
# accumulate stats
num_total += 1
num_correct += int(pred == label)
num_correct_norm += int(pred_norm == label)
print(f"{num_total} acc: {num_correct/num_total:.4f} acc_norm: {num_correct_norm/num_total:.4f}")
# debug prints
if num_total < 10:
print("---")
print(f"Context:\n {example['question']}")
print(f"Endings:")
for i, end in enumerate(example["endings"]):
print(f"{i} (loss: {avg_loss[i].item():.4f}) {end}")
print(f"predicted: {pred}, actual: {label}")
if __name__ == "__main__":
import argparse
parser = argparse.ArgumentParser()
parser.add_argument("-m", "--model_type", type=str, default="gpt2", help="the model type to use")
parser.add_argument("-d", "--device", type=str, default="cuda", help="the device to use")
args = parser.parse_args()
evaluate(args.model_type, args.device)