scripts/run_litert_lm_benchmark.py

#!/usr/bin/env python3
# Copyright 2026 The Dawn & Tint Authors
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"""Runs the LiteRT-LM performance tests.

This script acts as a thin wrapper around the litert_lm_advanced_main binary
to support running it on Swarming with correct libraries and paths.
"""

import argparse
import json
import os
from pathlib import Path
import shutil
import subprocess
import sys


def run_litert_lm(metric_proto_file_path: Path) -> subprocess.CompletedProcess:
    # The shared libraries (.so / .dylib) are isolated alongside the binary in the current
    # build out directory, so explicitly add them to the library path for execution on bots.
    env = os.environ.copy()
    env['LD_LIBRARY_PATH'] = f"{Path.cwd()}{os.pathsep}{env.get('LD_LIBRARY_PATH', '')}"
    env['DYLD_LIBRARY_PATH'] = f"{Path.cwd()}{os.pathsep}{env.get('DYLD_LIBRARY_PATH', '')}"

    # Disable host GPU driver shader disk caches so Init Executor deterministically
    # measures full cold shader compilation on every Swarming run.
    # NVIDIA shader cache.
    env['__GL_SHADER_DISK_CACHE'] = '0'

    # Mesa shader cache.
    env['MESA_SHADER_CACHE_DISABLE'] = 'true'

    # Mac shader cache.
    if sys.platform == 'darwin':
        try:
            darwin_cache = subprocess.check_output(
                ['getconf', 'DARWIN_USER_CACHE_DIR'], text=True).strip()
            for metal_cache in Path(darwin_cache).glob('**/com.apple.metal'):
                shutil.rmtree(metal_cache, ignore_errors=True)
        except Exception as e:
            print(f"Warning: Failed to clear Metal shader cache: {e}")

    repo_root = Path(__file__).resolve().parent.parent
    binary_name = ('litert_lm_advanced_main.exe'
                   if sys.platform == 'win32' else 'litert_lm_advanced_main')
    binary_path = Path.cwd() / binary_name
    model_path = repo_root / 'third_party' / 'litert-lm' / 'data' / 'model.litertlm'

    cmd = [
        str(binary_path),
        '--benchmark',
        '--benchmark_prefill_tokens=1024',
        '--benchmark_decode_tokens=256',
        '--backend=gpu',
        '--disable_cache=true',
        # Run pipeline compilation and weight upload synchronously during Init
        # Executor so background threads do not race with and spike Prefill speed.
        # TODO(crbug.com/562993169): Remove num_threads_to_compile and
        # num_threads_to_upload if this can be fixed upstream since it seems like
        # a benchmark bug.
        '--num_threads_to_compile=0',
        '--num_threads_to_upload=0',
        '--num_iterations=6',
        f'--model_path={model_path}',
        f'--metric_proto_file_path={metric_proto_file_path}',
    ]

    print(f"Executing: {' '.join(cmd)}")

    return subprocess.run(cmd, env=env, check=False)


def generate_results_for_resultdb_ingestion(success: bool,
                                            output_file: str) -> None:
    generated_test_results = {
        'failures': [],
        'valid': True,
    }
    if not success:
        generated_test_results['failures'].append('litert_lm_advanced_main')

    with open(output_file, 'w', encoding='utf-8') as outfile:
        json.dump(generated_test_results, outfile)


def main() -> None:
    parser = argparse.ArgumentParser(description='Runs LiteRT-LM benchmarks')

    parser.add_argument('--isolated-script-test-output',
                        help='Path to the location to output JSON results.')
    parser.add_argument('--isolated-script-test-perf-output',
                        help='Currently unused, needed for bot support.')
    parser.add_argument('--isolated-script-test-launcher-retry-limit',
                        help='Currently unused, needed for bot support.')
    parser.add_argument('--isolated-script-test-repeat',
                        help='Currently unused, needed for bot support.')
    parser.add_argument('--isolated-script-test-filter',
                        help='Currently unused, needed for bot support.')
    args = parser.parse_args()

    # Determine output directory for results.
    if args.isolated_script_test_output:
        output_dir = Path(args.isolated_script_test_output).parent
    else:
        output_dir = Path.cwd()

    # Run the benchmark and generate metric results file.
    metric_file = output_dir / 'litert_lm_metrics.pb'
    proc = run_litert_lm(metric_file)
    if args.isolated_script_test_output:
        generate_results_for_resultdb_ingestion(
            not proc.returncode, args.isolated_script_test_output)
    proc.check_returncode()


if __name__ == '__main__':
    main()