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Re: Guile Potluck 2021

From: Dr. Arne Babenhauserheide
Subject: Re: Guile Potluck 2021
Date: Sat, 27 Feb 2021 17:42:40 +0100
User-agent: mu4e 1.4.15; emacs 27.1

Hi Linus,

Linus Björnstam <> writes:
> I had a look and there is quite a lot you can do. Just out of
> curiosity: how much is GC time? You are generating a lot of
> intermediate data. Instead of vector-append! maybe use something like
> the new vectorlist srfi? If you show me a flame graph and give me some
> test data I can have a go!

Thank you!

I expect GC time to be roughly half during the trust calculation (much
more during import), because this fills up two cores.

I can’t easily give you a flame graph (except if you can tell me how to
generate it), but I now pushed a version in pure Scheme (instead of
wisp) that runs a huge test:

hg clone
cd wispwot
./run-wispwot.scm --test

This imports 200k trust edges (which takes a lot of time) and then does
three full trust calculations (which each take around 70s).

The most important limitation for optimization is that the memory use
must stay reasonable with 64k IDs which each have 1000 trust edges. This
memory use is what the current code is optimized for (that’s why there
are all those u8vectors and u16vectors).

For the math: at 64 million trust edges, this should currently require
(in theory) less than 200MiB of memory for the actual trust structure (2
byte for the id, 1 byte for the trust).

Going up to 300MiB for time-optimization would still be viable, but it
shouldn’t go beyond that (there are algorithmic options to reduce the
amount of work done per update, so the runtime of the current code is
important but it is not a life-and-death situation).

Best wishes,
Unpolitisch sein
heißt politisch sein
ohne es zu merken

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