contrib/hgperf

revset: add depth limit to descendants() (issue5374)

This is naive implementation using two-pass scanning. Tracking descendants
isn't an easy problem if both start and stop depths are specified. It's
impractical to remember all possible depths of each node while scanning from
roots to descendants because the number of depths explodes. Instead, we could
cache (min, max) depths as a good approximation and track ancestors back when
needed, but that's likely to have off-by-one bug.

Since this implementation appears not significantly slower, and is quite
straightforward, I think it's good enough for practical use cases. The time
and space complexity is O(n) ish.

  revisions:
  0) 1-pass scanning with (min, max)-depth cache (worst-case quadratic)
  1) 2-pass scanning (this version)

  repository:
  mozilla-central

  # descendants(0) (for reference)
  *) 0.430353

  # descendants(0, depth=1000)
  0) 0.264889
  1) 0.398289

  # descendants(limit(tip:0, 1, offset=10000), depth=1000)
  0) 0.025478
  1) 0.029099

  # descendants(0, depth=2000, startdepth=1000)
  0) painfully slow (due to quadratic backtracking of ancestors)
  1) 1.531138

#!/usr/bin/env python
#
# hgperf - measure performance of Mercurial commands
#
# Copyright 2014 Matt Mackall <[e-mail]>
#
# This software may be used and distributed according to the terms of the
# GNU General Public License version 2 or any later version.

'''measure performance of Mercurial commands

Using ``hgperf`` instead of ``hg`` measures performance of the target
Mercurial command. For example, the execution below measures
performance of :hg:`heads --topo`::

    $ hgperf heads --topo

All command output via ``ui`` is suppressed, and just measurement
result is displayed: see also "perf" extension in "contrib".

Costs of processing before dispatching to the command function like
below are not measured::

    - parsing command line (e.g. option validity check)
    - reading configuration files in

But ``pre-`` and ``post-`` hook invocation for the target command is
measured, even though these are invoked before or after dispatching to
the command function, because these may be required to repeat
execution of the target command correctly.
'''

import os
import sys

libdir = '@LIBDIR@'

if libdir != '@' 'LIBDIR' '@':
    if not os.path.isabs(libdir):
        libdir = os.path.join(os.path.dirname(os.path.realpath(__file__)),
                              libdir)
        libdir = os.path.abspath(libdir)
    sys.path.insert(0, libdir)

# enable importing on demand to reduce startup time
try:
    from mercurial import demandimport; demandimport.enable()
except ImportError:
    import sys
    sys.stderr.write("abort: couldn't find mercurial libraries in [%s]\n" %
                     ' '.join(sys.path))
    sys.stderr.write("(check your install and PYTHONPATH)\n")
    sys.exit(-1)

import mercurial.util
import mercurial.dispatch

def timer(func, title=None):
    results = []
    begin = mercurial.util.timer()
    count = 0
    while True:
        ostart = os.times()
        cstart = mercurial.util.timer()
        r = func()
        cstop = mercurial.util.timer()
        ostop = os.times()
        count += 1
        a, b = ostart, ostop
        results.append((cstop - cstart, b[0] - a[0], b[1]-a[1]))
        if cstop - begin > 3 and count >= 100:
            break
        if cstop - begin > 10 and count >= 3:
            break
    if title:
        sys.stderr.write("! %s\n" % title)
    if r:
        sys.stderr.write("! result: %s\n" % r)
    m = min(results)
    sys.stderr.write("! wall %f comb %f user %f sys %f (best of %d)\n"
                     % (m[0], m[1] + m[2], m[1], m[2], count))

orgruncommand = mercurial.dispatch.runcommand

def runcommand(lui, repo, cmd, fullargs, ui, options, d, cmdpats, cmdoptions):
    ui.pushbuffer()
    lui.pushbuffer()
    timer(lambda : orgruncommand(lui, repo, cmd, fullargs, ui,
                                 options, d, cmdpats, cmdoptions))
    ui.popbuffer()
    lui.popbuffer()

mercurial.dispatch.runcommand = runcommand

for fp in (sys.stdin, sys.stdout, sys.stderr):
    mercurial.util.setbinary(fp)

mercurial.dispatch.run()