Re: [HACKERS] A design for amcheck heapam verification

Peter Geoghegan wrote:

> > Your patch brings us one step closer to that goal.  (The book says
> > that this approach is good far sparse bitsets, but your comment says
> > that we expect something near 50%.  That's irrelevant anyway since a
> > future centralised popcount() implementation would do this in
> > word-sized chunks with a hardware instruction or branch-free-per-word
> > lookups in a table and not care at all about sparseness.)
> 
> I own a copy of Hacker's Delight (well, uh, Daniel Farina lent me his
> copy about 2 years ago!). pop()/popcount() does seem like a clever
> algorithm, that we should probably think about adopting in some cases,
> but I should point at that the current caller to my
> bloom_prop_bits_set() function is an elog() DEBUG1 call. This is not
> at all performance critical.

Eh, if you want to optimize it for the case where debug output is not
enabled, make sure to use ereport() not elog().  ereport()
short-circuits evaluation of arguments, whereas elog() does not.

-- 
Álvaro Herrera                https://www.2ndQuadrant.com/
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