Re: [Haskell-cafe] Libevent FFI problems
* Adam Langley [EMAIL PROTECTED] [080725 13:05]: 2008/7/25 Krzysztof Skrzętnicki [EMAIL PROTECTED]: Developing a high-performance web server in Concurrent Haskell http://www.haskell.org/~simonmar/papers/web-server-jfp.pdf (see page 15) Perhaps you might be interested in this paper also because of its topic. That's a good reference. Also note that the paper is 6 years old and GHC has come a long way since then. I'd suspect that the graph on page 15 would look much more favourable to Haskell these days. http://www.seas.upenn.edu/~lipeng/homepage/unify.html This paper (and included code) should be relevant and useful. There's an epoll wrapper and a lot of good stuff. ___ Haskell-Cafe mailing list Haskell-Cafe@haskell.org http://www.haskell.org/mailman/listinfo/haskell-cafe
[Haskell-cafe] Re: [ANN] bloomfilter 1.0 - Fast immutable and mutable Bloom filters
* Jim Snow [EMAIL PROTECTED] [080531 15:23]: Without looking at the code to verify that this is how it has really been implemented, a bloom filter is like a series of hash tables, where the hash table entries are one bit. The bit is set if there is an item that hashes to that value in the bloom filter. So, assuming a single hash table where half the bits are set, there's a 50% false positive rate and no false negatives when you do a membership test. To reduce the false positives, we can add another hash table with a different hash function. Assuming it also is half full, we can check if an item is in both tables, and our false positive rate drops to 25%. In practice, one might use something like 32 hash tables. This yields a false positive rate of 1/(2^32). Their most obvious application is to store the dictionary for a spell checker in a space-efficient way, though I have a friend who wrote a paper on using them for router caches. There was a google tech talk on bloom filters awhile ago: http://www.youtube.com/watch?v=947gWqwkhu0 One other use: LOAF is a simple extension to email that lets you append your entire address book to outgoing mail message without compromising your privacy. Correspondents can use this information to prioritize their mail, and learn more about their social networks. The LOAF home page is at http://loaf.cantbedone.org. ___ Haskell-Cafe mailing list Haskell-Cafe@haskell.org http://www.haskell.org/mailman/listinfo/haskell-cafe
Re: [Haskell-cafe] haskell version of fractal benchmark
* Andrew Coppin [EMAIL PROTECTED] [070608 02:45]:
Bayley, Alistair wrote:
[[1]mailto:[EMAIL PROTECTED] On Behalf Of Andrew Coppin
Donald Bruce Stewart wrote:
Some things to remember using Doubles:
* {-# OPTIONS -fexcess-precision #-}
* -fvia-C
* -fbang-patterns
* -optc-O2 -optc-mfpmath=sse -optc-msse2
* -optc-march=pentium4
1. What do all those things do?
2. Is the effect actually that large?
Large? Depends what you mean by large, but adding a few flags to get
just a 10-20% speedup isn't to be ignored:
Sure - if it really is 10-20%. (And not, say, 0.001 - 0.002%.)
A single data point for all of this, I have a program that calculates:
P^1_i = S_i/sum_k S_k
P^m_i = sum_{k!=i} P^1_k*P^m-1_i(S_~k)
Here's timings for the different options:
options run timecompile time
none 46.401 3.136
-O 5.033 4.906
-O24.967 6.755
-O2 -fexcess-precision 3.710 6.396
all listed options 3.602 6.344
Results with -fexcess-precision are very insignificantly different
(1.0 e-7).
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Re: [Haskell-cafe] New book: Real-World Haskell!
* Dan Weston [EMAIL PROTECTED] [070523 12:41]: What power animal have you chosen for the cover of your O'Reilly book? Alas, most of the good ones are gone already! I'd like to suggest the Mantis shrimp because they have excellent vision, they're long lived and they pack a punch. I haven't checked, but it's almost certainly not already used. http://en.wikipedia.org/wiki/Mantis_shrimp ___ Haskell-Cafe mailing list Haskell-Cafe@haskell.org http://www.haskell.org/mailman/listinfo/haskell-cafe
