Sorry, sent a premature reply. The problem is that some of those match blocks expand to using equal? which is a lot slower than using eqv? If we are doing it on every char in a 24mb file we are getting some serious constant factors.
match is a syntax-rules macro, so distinguishing literals are not possible. Concerning "the macro writer's bill of rights" I could maybe think this it would be a rather nice thing to turn equal? to eqv? when one argument is a char literal :D -- Linus Björnstam On Mon, 4 May 2020, at 11:36, Ludovic Courtès wrote: > Hey! > > Aleix Conchillo Flaqué <aconchi...@gmail.com> skribis: > > > So weird I'm getting different numbers on 2.2.7. Not sure how I'm getting > > those initial ~20s and you are getting consistent ~ 45s. It > > shouldn't have nothing to do with it, but could it be I'm running it on > > macOS? > > Did you add this ‘->bool’ call to ensure the resulting alist is not kept > in memory? > > > Now, it would be good to profile ‘json->scm’ to see if there’s anything > > that could be improved on the Guile side, or if it’s just a normal > > profile for GC-intensive code. > > > > Good news is that I have been working on performance improvements and > > json->scm is going down from my ~19 seconds to ~3 > > seconds on the same sample file. Linus Björnstam was the one to bring up > > performance issues so we've been back and forth trying to > > make it fast. > > Nice! > > > One thing I found is that `match` is slow. The code looked nicer but had to > > change it back to lets and conds as the performance > > increase was ~2 seconds. > > Oh, in which case exactly? And are you sure your hand-written code is > equivalent to the ‘match’ code (it’s common for hand-written code to be > more lax than ‘match’)? > > One thing to pay attention to is the use of ‘list?’, which is O(N), and > is implied by ellipses in ‘match’. If you want to use ‘match’ in a way > that avoids ‘list?’, write patterns such as (a . b) instead of (a b ...). > It doesn’t have the same meaning, but often the end result is the same, > for instance because you’ll later match on ‘b’ anyway. > > (I wish we can one day have a proper list type disjoint from pairs…) > > Thanks, > Ludo’. > >
