#!/usr/bin/env python
# time NUM_THREADS=3 python pcount.py big

import os, re, sys
from multiprocessing import Pool, cpu_count

if len(sys.argv) < 2: sys.exit(1)

def read_file (file, chunk_size=65536*16):
    """
    Lazy function generator to read a file in chunks,
    including to the end of line.
    """
    while True:
        chunk = file.read(chunk_size)
        if not chunk:
            break
        if not chunk.endswith('\n'):
            chunk += file.readline()
        yield chunk

def process_chunk(chunk):
    """
    Worker function to process chunks in parallel.
    """
    count = len(mul_re.findall(chunk))
    return count

mul_re = re.compile(r"mul\(\d{1,3},\d{1,3}\)")
num_processes = int(os.getenv('NUM_THREADS') or cpu_count())
p = Pool(num_processes)
file_name = sys.argv[1]

try:
    with open (file_name, "r") as file:
        results = p.map(process_chunk, read_file(file))
    p.close()
    p.join()
except Exception as e:
    print(e, file=sys.stderr)
    sys.exit(1)

print(f"Found {sum(results)} matches.")