Redex no longer has extra checks to eliminate redundant matches
(as those checks are prohibitively expensive for the lambdajs model)
so redundancy in the grammar can, when combined with context
decomposition or named patterns, lead to significant slowdowns
(cherry picked from commit 0c6e0a11cf)
This speeds up the lambdajs model considerably because the computation
to determine duplicates is expensive and no duplicates are really
ever dropped (and, in general, I think that duplicates will only
be dropped when the grammar is ambiguous; so maybe a better thing
is to just rewrite the grammar when that happens)
when one hole has been found
This improves the lambdajs model example's running time, presumably
because the hole is generally found near the "beginning" of the
term
Instead of using a hash-table, use the equal-hash-code directly;
this lets me evict entries only when they clobber each other,
and generally keep good cache utilization.
Also, cut the cache size by a factor of 5 while still having a
slight performance improvement on the r6rs test suite benchmark.
On that same benchmark, there are 1714812 misses in the cache, but
only 3485 times is an entry in the cache clobbered
have any holes, hide-holes, or names and, in that case, just
combining booleans instead of building of mtch structs.
This does seem to work on a simple benchmark. The code below
gets about 6x faster. But on the r6rs test suite, there is
no substantial change (possibly because the caching obviates
this optimization?)
lang racket/base
(require redex/reduction-semantics)
(caching-enabled? #f)
(define-language L (e (+ e e) number))
(define t
(let loop ([n 100])
(cond
[(zero? n) 1]
[else `(+ 11 ,(loop (- n 1)))])))
(define f (redex-match L e))
(time (for ([x (in-range 1000)]) (f t)))
When I enabled this, I don't see any speedup, on the R6RS test suite
benchmark (I see minor slowdown). Here are the numbers I get, on my
laptop:
nt cache: 35537 msec
neither: 844933 msec
Jay's idea: 875306 msec
And with both on, I see a similar, minor slowdown (as compared to the
version with the nt cache).
The main difference seems to be that I'm getting about 6 "hits" per
test case on the nt-match structs (that is, I avoid work by finding an
nt-match struct) and I'm getting about 8,800 hits in the cache per
test case.
redex patterns a bunch:
- repeats are turned into wrappers in sequences,
- names are all explicit,
- non-terminals are wrapped with `nt',
- cross patterns always have the hyphens in them.
- ellipses names are normalized (so there are no "hidden"
name equalities); this also means that repeat patterns
can have both a regular name and a mismatch name
Also, added a match-a-pattern helper macro that checks to make sure
that functions that process patterns don't miss any cases
This library is used by Redex, which wants a `syntax'-like template
language, but for datum values instead of syntax objects. Using
`datum-case' and `datum' generates much less code. Redex uses
only a small part of the general functionality, so adding
`syntax/datum' could be overkill. It's implemented by generalizing
the `syntax-case' and `syntax' pattern matching and template
constructing code, though; it's not a lot of extra code, and it's
easiest to generalize completely. We may find other uses for
datum templates, too.
when doing typesetting stuff in Redex, as the former seems to have
some kind of context dependency that makes it insert ||s around
some upper-case symbols sometimes
a) avoids creating big intermediate lists of the same things over and over
(this closes PR 12380)
b) generates less code (by generating calls to local functions)
c) normalizes its output (sorts by the printed representation)
(by expanding into a call to a 30 or so line procedure, instead of putting
that code directly into the result of the macro).
This produces about a 6x speedup on this reduction-relation
(reduction-relation L (--> 0 1) (--> 1 2) ... (--> 99 100))
where L is
(define-language L)
The time it takes to run "racket r6rs.rkt" in the shell from the
directory collects/redex/examples/r6rs speeds up by about 10% (15%
with errortrace enabled), in the case where all .zo files are built,
except the ones in the r6rs directory. (Also worth noting that "racket
-l redex" takes more than 50% of that time.) And the change has no
noticeable effect on the time it takes to run r6rs-test.rkt.
