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#!/usr/bin/env python
# Written by Michael Denkowski
#
# This file is part of moses. Its use is licensed under the GNU Lesser General
# Public License version 2.1 or, at your option, any later version.
'''Parallelize decoding with multiple instances of moses on a local machine
To use with mert-moses.pl, activate --multi-moses and set the number of moses
instances and threads per instance with --decoder-flags='--threads P:T:E'
This script runs a specified number of moses instances, each using one or more
threads. The highest speed is generally seen with many single-threaded
instances while the lowest memory usage is seen with a single many-threaded
instance. It is recommended to use the maximum number of instances that will
fit into memory (up to the number of available CPUs) and distribute CPUs across
them equally. For example, a machine with 32 CPUs that can fit 3 copies of
moses into memory would use --threads 2:11:10 for 2 instances with 11 threads
each and an extra instance with 10 threads (3 instances total using all CPUs).
Memory mapped models can be shared by multiple processes and increase the number
of instances that can fit into memory:
Mmaped phrase tables (Ulrich Germann)
http://www.statmt.org/moses/?n=Advanced.Incremental#ntoc3
Mmaped mapped language models (Kenneth Heafield)
http://www.statmt.org/moses/?n=FactoredTraining.BuildingLanguageModel#ntoc19
'''
import collections
import os
import Queue
import signal
import subprocess
import sys
import threading
import time
HELP = '''Multiple process decoding with Moses
Usage:
{} moses --config moses.ini [options] [decoder flags]
Options:
--threads P:T:E
P: Number of parallel instances to run
T: Number of threads per instance
E: Number of threads in optional extra instance
(default 1:1:0, overrides [threads] in moses.ini. Specifying T
and E is optional, e.g. --threads 16 starts 16 single-threaded
instances)
--n-best-list nbest.out N [distinct]: location and size of N-best list
--show-weights: for mert-moses.pl, just call moses and exit
Other options (decoder flags) are passed through to moses instances
'''
# Defaults
INPUT = sys.stdin
PROCS = 1
THREADS = 1
EXTRA = 0
DONE = threading.Event()
PID = os.getpid()
# A very long time, used as Queue operation timeout even though we don't
# actually want a timeout but we do want interruptibility
# (https://bugs.python.org/issue1360)
NEVER = 60 * 60 * 24 * 365 * 1000
# Single unit of computation: decode a line, output result, signal done
Task = collections.namedtuple('Task', ['id', 'line', 'out', 'event'])
def kill_main(msg):
'''kill -9 the main thread to stop everything immediately'''
sys.stderr.write('{}\n'.format(msg))
os.kill(PID, signal.SIGKILL)
def gzopen(f):
'''Open plain or gzipped text'''
return gzip.open(f, 'rb') if f.endswith('.gz') else open(f, 'r')
def run_instance(cmd_base, threads, tasks, cpu_affinity, cpu_offset, n_best=False):
'''Run an instance of moses that processes tasks (input lines) from a
queue using a specified number of threads'''
cmd = cmd_base[:]
cmd.append('--threads')
cmd.append(str(threads))
if cpu_affinity:
cmd.append('--cpu-affinity-offset')
cmd.append(str(cpu_offset))
print 'BEFORE'
print cmd
print 'AFTER\n'
try:
# Queue of tasks instance is currently working on, limited to the number
# of threads * 2 (minimal buffering). The queue should be kept full for
# optimal CPU usage.
work = Queue.Queue(maxsize=(threads * 2))
# Multi-threaded instance
moses = subprocess.Popen(cmd, stdin=subprocess.PIPE, stdout=subprocess.PIPE)
# Read and handle instance output as available
def handle_output():
while True:
# Output line triggers task completion
line = moses.stdout.readline()
# End of output (instance finished)
if not line:
break
task = work.get(timeout=NEVER)
if n_best:
# Read and copy lines until sentinel line, copy real line id
# id ||| hypothesis words ||| feature scores ||| total score
(first_i, rest) = line.split(' ||| ', 1)
task.out.append(' ||| '.join((task.id, rest)))
while True:
line = moses.stdout.readline()
(i, rest) = line.split(' ||| ', 1)
# Sentinel
if i != first_i:
break
task.out.append(' ||| '.join((task.id, rest)))
else:
task.out.append(line)
# Signal task done
task.event.set()
# Output thread
handler = threading.Thread(target=handle_output, args=())
# Daemon: guaranteed to finish before non-daemons
handler.setDaemon(True)
handler.start()
# Input thread: take tasks as they are available and add them to work
# queue. Stop when DONE encountered.
while True:
task = tasks.get(timeout=NEVER)
work.put(task, timeout=NEVER)
if task.event == DONE:
break
if n_best:
# Input line followed by blank line (sentinel)
moses.stdin.write(task.line)
moses.stdin.write('\n')
else:
moses.stdin.write(task.line)
# Cleanup
moses.stdin.close()
moses.wait()
handler.join()
except:
kill_main('Error with moses instance: see stderr')
def write_results(results, n_best=False, n_best_out=None):
'''Write out results (output lines) from a queue as they are populated'''
while True:
task = results.get(timeout=NEVER)
if task.event == DONE:
break
task.event.wait()
if n_best:
# Write top-best and N-best
# id ||| hypothesis words ||| feature scores ||| total score
top_best = task.out[0].split(' ||| ', 2)[1]
# Except don't write top-best if writing N-best to stdout "-"
if n_best_out != sys.stdout:
sys.stdout.write('{}\n'.format(top_best))
sys.stdout.flush()
for line in task.out:
n_best_out.write(line)
n_best_out.flush()
else:
sys.stdout.write(task.out[0])
sys.stdout.flush()
def main(argv):
# Defaults
moses_ini = None
input = INPUT
procs = PROCS
threads = THREADS
extra = EXTRA
n_best = False
n_best_file = None
n_best_size = None
n_best_distinct = False
n_best_out = None
show_weights = False
cpu_affinity = False
# Decoder command
cmd = argv[1:]
# Parse special options and remove from cmd
i = 1
while i < len(cmd):
if cmd[i] in ('-f', '-config', '--config'):
moses_ini = cmd[i + 1]
# Do not remove from cmd
i += 2
elif cmd[i] in ('-i', '-input-file', '--input-file'):
input = gzopen(cmd[i + 1])
cmd = cmd[:i] + cmd[i + 2:]
elif cmd[i] in ('-th', '-threads', '--threads'):
# P:T:E
args = cmd[i + 1].split(':')
procs = int(args[0])
if len(args) > 1:
threads = int(args[1])
if len(args) > 2:
extra = int(args[2])
cmd = cmd[:i] + cmd[i + 2:]
elif cmd[i] in ('-n-best-list', '--n-best-list'):
n_best = True
n_best_file = cmd[i + 1]
n_best_size = cmd[i + 2]
# Optional "distinct"
if i + 3 < len(cmd) and cmd[i + 3] == 'distinct':
n_best_distinct = True
cmd = cmd[:i] + cmd[i + 4:]
else:
cmd = cmd[:i] + cmd[i + 3:]
# Handled specially for mert-moses.pl
elif cmd[i] in ('-show-weights', '--show-weights'):
show_weights = True
# Do not remove from cmd
i += 1
elif cmd[i] in ('-cpu-affinity', '--cpu-affinity'):
cpu_affinity = True
cmd = cmd[:i] + cmd[i + 1:]
else:
i += 1
# If mert-moses.pl passes -show-weights, just call moses
if show_weights:
sys.stdout.write(subprocess.check_output(cmd))
sys.stdout.flush()
return
# Check inputs
if not (len(cmd) > 0 and moses_ini):
sys.stderr.write(HELP.format(os.path.basename(argv[0])))
sys.exit(2)
if not (os.path.isfile(cmd[0]) and os.access(cmd[0], os.X_OK)):
raise Exception('moses "{}" is not executable\n'.format(cmd[0]))
# Report settings
sys.stderr.write('Moses flags: {}\n'.format(' '.join('\'{}\''.format(s) if ' ' in s else s for s in cmd[1:])))
sys.stderr.write('Instances: {}\n'.format(procs))
sys.stderr.write('Threads per: {}\n'.format(threads))
if extra:
sys.stderr.write('Extra: {}\n'.format(extra))
if n_best:
sys.stderr.write('N-best list: {} ({}{})\n'.format(n_best_file, n_best_size, ', distinct' if n_best_distinct else ''))
# Task and result queues (buffer 8 * total threads input lines)
tasks = Queue.Queue(maxsize=(8 * ((procs * threads) + extra)))
results = Queue.Queue()
# N-best capture
if n_best:
cmd.append('--n-best-list')
cmd.append('-')
cmd.append(n_best_size)
if n_best_distinct:
cmd.append('distinct')
if n_best_file == '-':
n_best_out = sys.stdout
else:
n_best_out = open(n_best_file, 'w')
# Start instances
cpu_offset = -threads
instances = []
for i in range(procs + (1 if extra else 0)):
if cpu_affinity:
cpu_offset += threads
t = threading.Thread(target=run_instance, args=(cmd, (threads if i < procs else extra), tasks, cpu_affinity, cpu_offset, n_best))
instances.append(t)
# Daemon: guaranteed to finish before non-daemons
t.setDaemon(True)
t.start()
#time.sleep(1)
# Start results writer
writer = threading.Thread(target=write_results, args=(results, n_best, n_best_out))
writer.start()
# Main loop: queue task for each input line
id = 0
while True:
line = input.readline()
if not line:
break
# (input, out lines, err lines, "done" event)
task = Task(str(id), line, [], threading.Event())
results.put(task, timeout=NEVER)
tasks.put(task, timeout=NEVER)
id += 1
# Tell instances to exit
for t in instances:
tasks.put(Task(None, None, None, DONE), timeout=NEVER)
for t in instances:
t.join()
# Stop results writer
results.put(Task(None, None, None, DONE), timeout=NEVER)
writer.join()
# Cleanup
if n_best:
n_best_out.close()
if __name__ == '__main__':
try:
main(sys.argv)
except:
kill_main('Error with main I/O: see stderr')
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