Re: [RFC/PATCH 4/4] inexact rename detection eye candy

From: Jeff King <peff@peff.net>
Date: Feb 20, 2011, 09:48 UTC
Message-ID: <20110220094803.GA988@sigill.intra.peff.net>
In-Reply-To: <AANLkTik=pd3vVMERz=H3sp835Ft8OvrOzBE4PUS7vrO7@mail.gmail.com>

On Sat, Feb 19, 2011 at 07:57:57AM -0800, Linus Torvalds wrote:

Show 12 quoted lines

> > I made it update progress for each of the rename_src * rename_dst
> > similarity estimates. We could just as easily count rename_dst items we
> > look at, but hey, it's eye candy, and obviously bigger numbers are
> > better.
> 
> Uhh. My only big reaction to your patch was literally "why don't you
> just do it on the 'dst' items". I really don't think bigger numbers
> are better, and if you have _so_ many sources that each dst takes so
> long that you'd want updates at that granularity, you're too screwed
> anyway.
> 
> Don't make the "update progress" be part of the O(n^2) problem.

I timed it and it's not. The progress code is smart enough not to actually print anything more than once per second. So it's just an extra function call per loop, which is dwarfed by the massive estimate_similarity(). It's really not that tight a loop.

That being said, the output seems a little smoother to me hoisting it out, so I've put that in my re-roll. The bigger numbers are worth keeping, IMHO, as they are a more accurate reflection of how much work is being done. You do the same amount of work with 2 dests and 1000 sources as you do with 1000 dests and 2 sources. But one will count to 1000, and the other will count to 2. They should probably both count to 2000, the number of estimate_similarity() calls we must make, which is the expensive part. (Actually that is not quite accurate, as we may skip some calls for destinations already found, but it's not worth the effort to figure out how many calls we'll actually make ahead of time).

So here is the re-roll, which I think is probably OK for inclusion. It replaces 4/4 from my last series.

  [1/3]: add inexact rename detection progress infrastructure
  [2/3]: merge: enable progress reporting for rename detection
  [3/3]: pull: propagate --progress to merge

-Peff