[test] Added test_needle_ref.py.

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Zijie Tian
2026-01-02 22:03:23 +08:00
parent 74ee6d0895
commit ff8b09cd35
2 changed files with 320 additions and 1 deletions

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"""
Needle-in-a-haystack reference test using pure torch + transformers.
This is a reference implementation for comparison with nanovllm.
Uses standard HuggingFace inference (no custom KV cache, no offload).
"""
import os
import argparse
import torch
from transformers import AutoModelForCausalLM, AutoTokenizer
# ============================================================
# Needle Test Generator
# ============================================================
def generate_needle_prompt(
tokenizer,
target_length: int,
needle_position: float = 0.5,
needle_value: str = "7492",
use_chat_template: bool = True,
) -> tuple[str, str]:
"""
Generate a needle-in-haystack prompt of approximately target_length tokens.
Args:
tokenizer: HuggingFace tokenizer for length estimation
target_length: Target total sequence length in tokens
needle_position: Where to place needle (0.0=start, 0.5=middle, 1.0=end)
needle_value: The secret value to hide in the haystack
use_chat_template: Whether to use chat template for instruct models
Returns:
(prompt, expected_answer): The full prompt and the expected needle value
"""
# Haystack filler paragraphs (various topics to create realistic context)
haystack_paragraphs = [
"The weather today is quite pleasant with clear skies and moderate temperatures. "
"Many people are enjoying outdoor activities in the park. "
"Birds are singing in the trees and children are playing on the swings. ",
"In the world of technology, new innovations continue to emerge every day. "
"Researchers are working on advanced algorithms and computing systems. "
"The future of artificial intelligence looks promising with many breakthroughs. ",
"The history of human civilization spans thousands of years. "
"Ancient cultures developed writing, mathematics, and astronomy. "
"Trade routes connected distant lands and facilitated cultural exchange. ",
"Modern cooking combines traditional techniques with new ingredients. "
"Chefs around the world experiment with flavors and presentations. "
"Food brings people together and creates memorable experiences. ",
"The ocean covers more than seventy percent of Earth's surface. "
"Marine ecosystems support an incredible diversity of life forms. "
"Scientists continue to discover new species in the deep sea. ",
"Music has been a part of human culture since prehistoric times. "
"Different genres evolved across various regions and time periods. "
"Today, people can access millions of songs through digital platforms. ",
"Space exploration has revealed many secrets about our universe. "
"Telescopes can observe galaxies billions of light years away. "
"Future missions aim to establish human presence on other planets. ",
"The study of languages reveals patterns in human cognition. "
"Linguists analyze grammar, semantics, and phonetics across cultures. "
"Language continues to evolve with new words and expressions. ",
]
# The needle sentence
needle = f"The secret number you need to remember is {needle_value}. This is very important. "
# Estimate tokens for fixed parts
needle_tokens = len(tokenizer.encode(needle, add_special_tokens=False))
question_text = "What is the secret number mentioned in the text above? Answer with just the number."
question_tokens = len(tokenizer.encode(question_text, add_special_tokens=False))
# Buffer for chat template, special tokens, etc.
overhead_tokens = 100 if use_chat_template else 50
# Available tokens for haystack
haystack_target_tokens = target_length - needle_tokens - question_tokens - overhead_tokens
if haystack_target_tokens < 100:
raise ValueError(f"target_length {target_length} is too short for needle test")
# Build haystack by repeating paragraphs
haystack_parts = []
current_tokens = 0
para_idx = 0
while current_tokens < haystack_target_tokens:
para = haystack_paragraphs[para_idx % len(haystack_paragraphs)]
para_tokens = len(tokenizer.encode(para, add_special_tokens=False))
if current_tokens + para_tokens > haystack_target_tokens:
break
haystack_parts.append(para)
current_tokens += para_tokens
para_idx += 1
# Calculate needle insertion point
needle_idx = int(len(haystack_parts) * needle_position)
needle_idx = max(0, min(needle_idx, len(haystack_parts)))
# Insert needle
haystack_parts.insert(needle_idx, needle)
# Assemble prompt
full_text = "".join(haystack_parts)
if use_chat_template and hasattr(tokenizer, 'apply_chat_template'):
# Use chat template for instruct models
# For Qwen3, add /no_think to disable thinking mode
question_text = "/no_think Answer only with the secret number mentioned above, nothing else:"
messages = [
{"role": "user", "content": f"{full_text}\n\n{question_text}"}
]
prompt = tokenizer.apply_chat_template(
messages,
tokenize=False,
add_generation_prompt=True,
)
else:
# Raw text format for base models
question = "\n\nQuestion: What is the secret number mentioned in the text above?\nAnswer: The secret number is"
prompt = full_text + question
# Verify length
actual_tokens = len(tokenizer.encode(prompt, add_special_tokens=False))
print(f"[NeedleTest] Target: {target_length} tokens, Actual: {actual_tokens} tokens")
print(f"[NeedleTest] Needle position: {needle_position:.0%} ({needle_idx}/{len(haystack_parts)-1} paragraphs)")
print(f"[NeedleTest] Using chat template: {use_chat_template and hasattr(tokenizer, 'apply_chat_template')}")
return prompt, needle_value
def check_needle_answer(output_text: str, expected: str) -> bool:
"""Check if the model output contains the expected needle value."""
import re
# Clean output - remove special tokens and whitespace
output_clean = output_text.replace('<|im_end|>', '').replace('\r', ' ').replace('\n', ' ')
output_clean = ' '.join(output_clean.split()).lower()
expected_clean = expected.strip().lower()
# Check if expected value appears in output
if expected_clean in output_clean:
return True
# Try to extract numbers and check if expected is among them
numbers = re.findall(r'\d+', output_clean)
return expected_clean in numbers
# ============================================================
# Main Test
# ============================================================
def run_needle_test(
model_path: str,
input_len: int,
needle_position: float = 0.5,
needle_value: str = "7492",
max_new_tokens: int = 32,
dtype: str = "auto",
verbose: bool = True,
) -> bool:
"""
Run a needle-in-haystack test using standard transformers inference.
Args:
model_path: Path to model
input_len: Target input sequence length
needle_position: Where to place needle (0.0-1.0)
needle_value: The secret value to find
max_new_tokens: Maximum tokens to generate
dtype: Model dtype ("auto", "float16", "bfloat16")
verbose: Print detailed output
Returns:
True if test passed, False otherwise
"""
if verbose:
print(f"\n{'='*60}")
print(f"Needle-in-Haystack Reference Test (torch + transformers)")
print(f"{'='*60}")
print(f"Model: {model_path}")
print(f"Input length: {input_len}")
print(f"Needle position: {needle_position:.0%}")
print(f"Needle value: {needle_value}")
print(f"Dtype: {dtype}")
print(f"{'='*60}\n")
# 1. Load tokenizer
print("[1/4] Loading tokenizer...")
tokenizer = AutoTokenizer.from_pretrained(model_path, trust_remote_code=True)
# 2. Generate needle prompt
print("[2/4] Generating needle prompt...")
prompt, expected = generate_needle_prompt(
tokenizer=tokenizer,
target_length=input_len,
needle_position=needle_position,
needle_value=needle_value,
)
# 3. Load model
print("[3/4] Loading model...")
torch_dtype = {
"auto": "auto",
"float16": torch.float16,
"bfloat16": torch.bfloat16,
}.get(dtype, "auto")
model = AutoModelForCausalLM.from_pretrained(
model_path,
torch_dtype=torch_dtype,
device_map="auto",
trust_remote_code=True,
)
model.eval()
# 4. Generate output
print("[4/4] Running inference...")
input_ids = tokenizer.encode(prompt, return_tensors="pt").to(model.device)
print(f" Input shape: {input_ids.shape}")
with torch.no_grad():
output_ids = model.generate(
input_ids,
max_new_tokens=max_new_tokens,
temperature=0.6,
do_sample=True,
pad_token_id=tokenizer.eos_token_id,
)
# Decode only the new tokens
new_token_ids = output_ids[0, input_ids.shape[1]:]
output_text = tokenizer.decode(new_token_ids, skip_special_tokens=False)
# 5. Check result
passed = check_needle_answer(output_text, expected)
if verbose:
print(f"\n{'='*60}")
print(f"Result")
print(f"{'='*60}")
print(f"Expected: {expected}")
print(f"Output tokens ({len(new_token_ids)}): {new_token_ids[:20].tolist()}")
print(f"Output: {output_text[:200]}...")
print(f"Status: {'PASSED' if passed else 'FAILED'}")
print(f"{'='*60}\n")
return passed
# ============================================================
# CLI Entry Point
# ============================================================
if __name__ == "__main__":
parser = argparse.ArgumentParser(
description="Needle-in-haystack reference test (torch + transformers)"
)
parser.add_argument(
"--model", "-m",
type=str,
default=os.path.expanduser("~/models/Qwen3-4B-Instruct-2507/"),
help="Path to model"
)
parser.add_argument(
"--input-len",
type=int,
default=8 * 1024,
help="Target input sequence length"
)
parser.add_argument(
"--needle-position",
type=float,
default=0.5,
help="Needle position (0.0=start, 0.5=middle, 1.0=end)"
)
parser.add_argument(
"--needle-value",
type=str,
default="7492",
help="The secret value to hide"
)
parser.add_argument(
"--max-new-tokens",
type=int,
default=32,
help="Maximum tokens to generate"
)
parser.add_argument(
"--dtype",
type=str,
default="auto",
choices=["auto", "float16", "bfloat16"],
help="Model dtype"
)
args = parser.parse_args()
passed = run_needle_test(
model_path=args.model,
input_len=args.input_len,
needle_position=args.needle_position,
needle_value=args.needle_value,
max_new_tokens=args.max_new_tokens,
dtype=args.dtype,
verbose=True,
)
if passed:
print("test_needle_ref: PASSED")
else:
print("test_needle_ref: FAILED")
exit(1)