Re: [Haskell-cafe] darcs patch dependencies in dot format

On 17 May 2012 03:31, Stephen Tetley wrote:

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On 16 May 2012 19:43, wren ng thornton wrote:

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You should probably farm out the toDot rendering to one of the libraries that focuses on that[1], since they'll have focused on the efficiency issues--- or if they haven't, then you can contribute improvements there, helping everyone win. In particular, you're using Strings which is a notorious performance sink. Using Text or ByteStrings would be far better.

I'm not sure swapping to Text or ByteStrings make be much great shakes for this. If you are generating huge files, where it would count - then the files are going to be a real problem for Graphviz to render (unless Graphviz has seen some optimization recently...).

I found with graphviz that switching to Text gave two advantages: 1) Easier to require UTF-8 usage 2) Printing and parsing was faster In part, the speed-up came from switching to wl-pprint-text rather than pretty (the wl-pprint method of pretty-printing seems to have some efficiency improvements in how concatenation is done over pretty) and the Text backend for polyparse lets you use manySatisfy rather than (many . satisfy) which is more efficient. But even in my initial pseudo-port (going via String a lot, etc.) there was a slight speed-up. So I think there is still a valid reason to consider using Text (or possibly ByteString, but I think that has potential issues).

That said, I would recommend Sönke uses a pretty print library rather than Printf as using the former makes for much more idiomatic for Haskell and generally performs well enough for "generational" activities even if it uses Strings internally.

Best wishes

Stephen

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