[PATCH 4 of 5] topoiter: support for non-contiguous revset

Pierre-Yves David pierre-yves.david at ens-lyon.org
Thu Nov 20 02:10:46 CST 2014



On 11/19/2014 10:49 PM, Martin von Zweigbergk wrote:
> Sorry, just some naive comments and questions below.
>
> On Tue Nov 18 2014 at 3:57:18 PM Pierre-Yves David
> <pierre-yves.david at ens-lyon.org <mailto:pierre-yves.david at ens-lyon.org>>
> wrote:
>
>     # HG changeset patch
>     # User Pierre-Yves David <pierre-yves.david at fb.com
>     <mailto:pierre-yves.david at fb.com>>
>     # Date 1409850336 -7200
>     #      Thu Sep 04 19:05:36 2014 +0200
>     # Node ID 026932aa1c4f05cf930c5853ae8946__36399de111
>     # Parent  ee131567469924b1642956ad5adfa9__f6122ba6d3
>     topoiter: support for non-contiguous revset
>
>     The algorithm now work when some revision are skipped. We now use "first
>     included ancestors" instead of just "parent" to link changesets with
>     each other.
>
>     diff --git a/mercurial/graphmod.py b/mercurial/graphmod.py
>     --- a/mercurial/graphmod.py
>     +++ b/mercurial/graphmod.py
>     @@ -18,17 +18,17 @@ Data depends on type.
>       """
>
>       from mercurial.node import nullrev
>       import util
>
>     +import heapq
>     +
>       CHANGESET = 'C'
>
>       def topoiter(revs, parentsfunc):
>           """topologically iter over a set of revision, one branch at a
>     time.
>
>     -    Currently does not handle non contigious <revs> input.
>     -
>           Currently consider every changeset under a merge to be on the
>     same branch
>           using revision number to sort them.
>
>           Could be easily extend to give priority to an initial branch.
>
>     @@ -89,20 +89,31 @@ def topoiter(revs, parentsfunc):
>           # and the <blocked> set contains the parents revisions of
>     already emitted
>           # revision.
>           #
>           # You could pre-seed the <parents> set of groups[0] to a specific
>           # changesets to select what the first emitted branch should be.
>     -    #
>     -    # We do not support revisions will hole yet, but adding such
>     support
>     -    # would be easy. The iteration will have to be done using both
>     input
>     -    # revision and parents (see cl.ancestors function + a few
>     tweaks) but
>     -    # only revisions parts of the initial set should be emitted.
>           groups = [([], unblocked)]
>     -    for current in revs:
>     -        if True:
>     -            # Look for a group awaiting on the current revision.
>     -            matching = [i for i, g in enumerate(groups) if current
>     in g[1]]
>     +    pendingheap = []
>     +    pendingset = set()
>     +
>     +    heapq.heapify(pendingheap)
>
>
> Not really necessary since pendingheap is already a valid heap, but I'm
> new to Python so I don't know what's considered best practice.

Yeah but better safe than sorry. It does not hurt to be over explicit 
about this being a heap.

>     +    heappop = heapq.heappop
>     +    heappush = heapq.heappush
>
>
> Is this functionally equivalent to "from heapq import heappop" etc?
> Faster? You want the smaller scope?

It equivalent.
It is faster too because python is bad at lookup.

>
>     +    for currentrev in revs:
>     +        # heap works with smallest element, we want highest so we
>     invert
>     +        if currentrev not in pendingset:
>     +            heappush(pendingheap, -currentrev)
>     +            pendingset.add(currentrev)
>     +        # iterates on pending rev until after the current rev have been
>     +        # processeed.
>     +        rev = None
>     +        while rev != currentrev:
>     +            rev = -heappop(pendingheap)
>     +            pendingset.remove(rev)
>     +
>     +            # seek for a group awaiting on the current revision.
>
>
> Should 'Look' have been 'seek' in 1/5 instead? Or did you do it on
> purpose to make the patch easier to read?

It should have been seek. (Not super critical)

>
>     +            matching = [i for i, g in enumerate(groups) if rev in g[1]]
>
>                   if matching:
>                       # The main idea is to gather together all set that
>     await on the
>                       # same revision.
>                       #
>     @@ -128,23 +139,29 @@ def topoiter(revs, parentsfunc):
>                       for i in reversed(matching):
>                           del groups[i]
>                   else:
>                       # his is a new head we create a new group for it.
>                       targetidx = len(groups)
>     -                groups.append(([], set([current])))
>     +                groups.append(([], set([rev])))
>
>
> Would s/current/rev/ had made sense in 1/5 to reduce this patch a bit?

No, rev is something we want emitted, current is either rev or a skipped 
parent of rev.

>
>
>                   gr = groups[targetidx]
>
>                   # We now adds the current nodes to this groups. This
>     is done after
>                   # the group merging because all elements from a group
>     that relied
>                   # on this rev must preceed it.
>                   #
>                   # we also update the <parents> set to includes the
>     parents on the
>                   # new nodes.
>     -            gr[0].append(current)
>     -            gr[1].remove(current)
>     -            gr[1].update([p for p in parentsfunc(current) if p >
>     nullrev])
>     +            if rev == currentrev: # only display stuff in rev
>     +                gr[0].append(rev)
>     +            gr[1].remove(rev)
>     +            parents = [p for p in parentsfunc(rev) if p > nullrev]
>
>     +            gr[1].update(parents)
>     +            for p in parents:
>     +                if p not in pendingset:
>     +                    pendingset.add(p)
>     +                    heappush(pendingheap, -p)
>
>                   # Look for a group to display
>                   #
>                   # When unblocked is empty (if clause), We are not
>     waiting over any
>                   # revision during the first iteration (if no priority
>     was given) or
>     @@ -173,10 +190,15 @@ def topoiter(revs, parentsfunc):
>                       # unless it is group[0] in which case you just
>     empty it.
>                       if targetidx:
>                           del groups[targetidx]
>                       else:
>                           gr[0][:] = []
>     +    # Check if we have some group waiting for revision we are not
>     going to
>     +    # iterate over
>     +    for g in groups:
>     +        for r in g[0]:
>     +            yield r
>
>       def dagwalker(repo, revs):
>           """cset DAG generator yielding (id, CHANGESET, ctx,
>     [parentids]) tuples
>
>           This generator function walks through revisions (which should
>     be ordered
>     diff --git a/tests/test-glog-topological.__t
>     b/tests/test-glog-topological.__t
>     --- a/tests/test-glog-topological.__t
>     +++ b/tests/test-glog-topological.__t
>     @@ -35,10 +35,13 @@ later.
>         | |
>         o |  1
>         |/
>         o  0
>
>     +
>     +(display all nodes)
>     +
>         $ hg --config experimental.graph-__topological=1 log -G
>         o  8
>         |
>         o  3
>         |
>     @@ -54,5 +57,24 @@ later.
>         | |
>         | o  4
>         |/
>         o  0
>
>     +
>     +(revset skipping nodes)
>     +
>     +  $ hg --config experimental.graph-__topological=1 log -G --rev
>     'not (2+6)'
>
>
> Sorry, but I didn't quite understand the algorithm. Would it also work
> well and efficiently with e.g. 'hg log hgext/'? I don't know enough
> about revsets, I suppose.

Sure it just work with a list of revs and parentrev function. The revset 
used for 'hgext/' should be lazy so we are all good.

-- 
Pierre-Yves David


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