Patchwork D2288: pvec: delete module

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Submitter phabricator
Date Feb. 16, 2018, 7:41 p.m.
Message ID <differential-rev-PHID-DREV-zkhxtldwgdd4au2x74hn-req@phab.mercurial-scm.org>
Download mbox | patch
Permalink /patch/27993/
State Superseded
Headers show

Comments

phabricator - Feb. 16, 2018, 7:41 p.m.
martinvonz created this revision.
Herald added a subscriber: mercurial-devel.
Herald added a reviewer: hg-reviewers.

REVISION SUMMARY
  The pvec module was introduced in https://phab.mercurial-scm.org/rHG0d175ac527c1d1b51b1de6dff25907ae377b9280 (pvec: introduce pvecs,
  2012-03-12), but it seems it was never used. Let's delete it to avoid
  wasting time cleaning it up in the future.

REPOSITORY
  rHG Mercurial

REVISION DETAIL
  https://phab.mercurial-scm.org/D2288

AFFECTED FILES
  mercurial/debugcommands.py
  mercurial/pvec.py
  tests/test-completion.t
  tests/test-help.t

CHANGE DETAILS




To: martinvonz, #hg-reviewers
Cc: mercurial-devel
phabricator - Feb. 16, 2018, 9:52 p.m.
durin42 added a comment.


  So....I actually have an idea involving pvec and obsmarker metadata in `hg export` output. I'll work on fixing any problems in pvec, can we keep it around a little longer?

REPOSITORY
  rHG Mercurial

REVISION DETAIL
  https://phab.mercurial-scm.org/D2288

To: martinvonz, #hg-reviewers
Cc: durin42, mercurial-devel
phabricator - Feb. 16, 2018, 10:03 p.m.
martinvonz added a comment.


  In https://phab.mercurial-scm.org/D2288#37819, @durin42 wrote:
  
  > So....I actually have an idea involving pvec and obsmarker metadata in `hg export` output. I'll work on fixing any problems in pvec, can we keep it around a little longer?
  
  
  Definitely. It hasn't bothered me at all personally. I just saw it in the list of files and wondered what it was.
  
  The first two patches in this series should still make sense.

REPOSITORY
  rHG Mercurial

REVISION DETAIL
  https://phab.mercurial-scm.org/D2288

To: martinvonz, #hg-reviewers
Cc: durin42, mercurial-devel
phabricator - March 15, 2018, 7:18 p.m.
pulkit abandoned this revision.
pulkit added a comment.


  This is not required as @durin42 will like to use pvec.

REPOSITORY
  rHG Mercurial

REVISION DETAIL
  https://phab.mercurial-scm.org/D2288

To: pulkit, #hg-reviewers, martinvonz
Cc: durin42, mercurial-devel

Patch

diff --git a/tests/test-help.t b/tests/test-help.t
--- a/tests/test-help.t
+++ b/tests/test-help.t
@@ -953,7 +953,6 @@ 
    debugpickmergetool
                  examine which merge tool is chosen for specified file
    debugpushkey  access the pushkey key/value protocol
-   debugpvec     (no help text available)
    debugrebuilddirstate
                  rebuild the dirstate as it would look like for the given
                  revision
diff --git a/tests/test-completion.t b/tests/test-completion.t
--- a/tests/test-completion.t
+++ b/tests/test-completion.t
@@ -105,7 +105,6 @@ 
   debugpeer
   debugpickmergetool
   debugpushkey
-  debugpvec
   debugrebuilddirstate
   debugrebuildfncache
   debugrename
@@ -285,7 +284,6 @@ 
   debugpeer: 
   debugpickmergetool: rev, changedelete, include, exclude, tool
   debugpushkey: 
-  debugpvec: 
   debugrebuilddirstate: rev, minimal
   debugrebuildfncache: 
   debugrename: rev
diff --git a/mercurial/pvec.py b/mercurial/pvec.py
deleted file mode 100644
--- a/mercurial/pvec.py
+++ /dev/null
@@ -1,214 +0,0 @@ 
-# pvec.py - probabilistic vector clocks for Mercurial
-#
-# Copyright 2012 Matt Mackall <mpm@selenic.com>
-#
-# This software may be used and distributed according to the terms of the
-# GNU General Public License version 2 or any later version.
-
-'''
-A "pvec" is a changeset property based on the theory of vector clocks
-that can be compared to discover relatedness without consulting a
-graph. This can be useful for tasks like determining how a
-disconnected patch relates to a repository.
-
-Currently a pvec consist of 448 bits, of which 24 are 'depth' and the
-remainder are a bit vector. It is represented as a 70-character base85
-string.
-
-Construction:
-
-- a root changeset has a depth of 0 and a bit vector based on its hash
-- a normal commit has a changeset where depth is increased by one and
-  one bit vector bit is flipped based on its hash
-- a merge changeset pvec is constructed by copying changes from one pvec into
-  the other to balance its depth
-
-Properties:
-
-- for linear changes, difference in depth is always <= hamming distance
-- otherwise, changes are probably divergent
-- when hamming distance is < 200, we can reliably detect when pvecs are near
-
-Issues:
-
-- hamming distance ceases to work over distances of ~ 200
-- detecting divergence is less accurate when the common ancestor is very close
-  to either revision or total distance is high
-- this could probably be improved by modeling the relation between
-  delta and hdist
-
-Uses:
-
-- a patch pvec can be used to locate the nearest available common ancestor for
-  resolving conflicts
-- ordering of patches can be established without a DAG
-- two head pvecs can be compared to determine whether push/pull/merge is needed
-  and approximately how many changesets are involved
-- can be used to find a heuristic divergence measure between changesets on
-  different branches
-'''
-
-from __future__ import absolute_import
-
-from .node import nullrev
-from . import (
-    util,
-)
-
-_size = 448 # 70 chars b85-encoded
-_bytes = _size / 8
-_depthbits = 24
-_depthbytes = _depthbits / 8
-_vecbytes = _bytes - _depthbytes
-_vecbits = _vecbytes * 8
-_radius = (_vecbits - 30) / 2 # high probability vectors are related
-
-def _bin(bs):
-    '''convert a bytestring to a long'''
-    v = 0
-    for b in bs:
-        v = v * 256 + ord(b)
-    return v
-
-def _str(v, l):
-    bs = ""
-    for p in xrange(l):
-        bs = chr(v & 255) + bs
-        v >>= 8
-    return bs
-
-def _split(b):
-    '''depth and bitvec'''
-    return _bin(b[:_depthbytes]), _bin(b[_depthbytes:])
-
-def _join(depth, bitvec):
-    return _str(depth, _depthbytes) + _str(bitvec, _vecbytes)
-
-def _hweight(x):
-    c = 0
-    while x:
-        if x & 1:
-            c += 1
-        x >>= 1
-    return c
-_htab = [_hweight(x) for x in xrange(256)]
-
-def _hamming(a, b):
-    '''find the hamming distance between two longs'''
-    d = a ^ b
-    c = 0
-    while d:
-        c += _htab[d & 0xff]
-        d >>= 8
-    return c
-
-def _mergevec(x, y, c):
-    # Ideally, this function would be x ^ y ^ ancestor, but finding
-    # ancestors is a nuisance. So instead we find the minimal number
-    # of changes to balance the depth and hamming distance
-
-    d1, v1 = x
-    d2, v2 = y
-    if d1 < d2:
-        d1, d2, v1, v2 = d2, d1, v2, v1
-
-    hdist = _hamming(v1, v2)
-    ddist = d1 - d2
-    v = v1
-    m = v1 ^ v2 # mask of different bits
-    i = 1
-
-    if hdist > ddist:
-        # if delta = 10 and hdist = 100, then we need to go up 55 steps
-        # to the ancestor and down 45
-        changes = (hdist - ddist + 1) / 2
-    else:
-        # must make at least one change
-        changes = 1
-    depth = d1 + changes
-
-    # copy changes from v2
-    if m:
-        while changes:
-            if m & i:
-                v ^= i
-                changes -= 1
-            i <<= 1
-    else:
-        v = _flipbit(v, c)
-
-    return depth, v
-
-def _flipbit(v, node):
-    # converting bit strings to longs is slow
-    bit = (hash(node) & 0xffffffff) % _vecbits
-    return v ^ (1<<bit)
-
-def ctxpvec(ctx):
-    '''construct a pvec for ctx while filling in the cache'''
-    r = ctx.repo()
-    if not util.safehasattr(r, "_pveccache"):
-        r._pveccache = {}
-    pvc = r._pveccache
-    if ctx.rev() not in pvc:
-        cl = r.changelog
-        for n in xrange(ctx.rev() + 1):
-            if n not in pvc:
-                node = cl.node(n)
-                p1, p2 = cl.parentrevs(n)
-                if p1 == nullrev:
-                    # start with a 'random' vector at root
-                    pvc[n] = (0, _bin((node * 3)[:_vecbytes]))
-                elif p2 == nullrev:
-                    d, v = pvc[p1]
-                    pvc[n] = (d + 1, _flipbit(v, node))
-                else:
-                    pvc[n] = _mergevec(pvc[p1], pvc[p2], node)
-    bs = _join(*pvc[ctx.rev()])
-    return pvec(util.b85encode(bs))
-
-class pvec(object):
-    def __init__(self, hashorctx):
-        if isinstance(hashorctx, str):
-            self._bs = hashorctx
-            self._depth, self._vec = _split(util.b85decode(hashorctx))
-        else:
-            self._vec = ctxpvec(hashorctx)
-
-    def __str__(self):
-        return self._bs
-
-    def __eq__(self, b):
-        return self._vec == b._vec and self._depth == b._depth
-
-    def __lt__(self, b):
-        delta = b._depth - self._depth
-        if delta < 0:
-            return False # always correct
-        if _hamming(self._vec, b._vec) > delta:
-            return False
-        return True
-
-    def __gt__(self, b):
-        return b < self
-
-    def __or__(self, b):
-        delta = abs(b._depth - self._depth)
-        if _hamming(self._vec, b._vec) <= delta:
-            return False
-        return True
-
-    def __sub__(self, b):
-        if self | b:
-            raise ValueError("concurrent pvecs")
-        return self._depth - b._depth
-
-    def distance(self, b):
-        d = abs(b._depth - self._depth)
-        h = _hamming(self._vec, b._vec)
-        return max(d, h)
-
-    def near(self, b):
-        dist = abs(b.depth - self._depth)
-        if dist > _radius or _hamming(self._vec, b._vec) > _radius:
-            return False
diff --git a/mercurial/debugcommands.py b/mercurial/debugcommands.py
--- a/mercurial/debugcommands.py
+++ b/mercurial/debugcommands.py
@@ -54,7 +54,6 @@ 
     obsutil,
     phases,
     policy,
-    pvec,
     pycompat,
     registrar,
     repair,
@@ -1812,27 +1811,6 @@ 
             ui.write("%s\t%s\n" % (util.escapestr(k),
                                    util.escapestr(v)))
 
-@command('debugpvec', [], _('A B'))
-def debugpvec(ui, repo, a, b=None):
-    ca = scmutil.revsingle(repo, a)
-    cb = scmutil.revsingle(repo, b)
-    pa = pvec.ctxpvec(ca)
-    pb = pvec.ctxpvec(cb)
-    if pa == pb:
-        rel = "="
-    elif pa > pb:
-        rel = ">"
-    elif pa < pb:
-        rel = "<"
-    elif pa | pb:
-        rel = "|"
-    ui.write(_("a: %s\n") % pa)
-    ui.write(_("b: %s\n") % pb)
-    ui.write(_("depth(a): %d depth(b): %d\n") % (pa._depth, pb._depth))
-    ui.write(_("delta: %d hdist: %d distance: %d relation: %s\n") %
-             (abs(pa._depth - pb._depth), pvec._hamming(pa._vec, pb._vec),
-              pa.distance(pb), rel))
-
 @command('debugrebuilddirstate|debugrebuildstate',
     [('r', 'rev', '', _('revision to rebuild to'), _('REV')),
      ('', 'minimal', None, _('only rebuild files that are inconsistent with '