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cs: speed up hash-map and hash-for-each on mutable hash tables

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Specialize internal iteration to avoid the overhead of going though
the `hash-iterate-...` interface for each step.
This commit is contained in:
Matthew Flatt 2019-12-28 09:17:41 -06:00
parent 8b3fd15803
commit 085dd494d7
1 changed files with 30 additions and 0 deletions
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30
racket/src/cs/rumble/hash.ss
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@ -398,6 +398,8 @@
(for-each (lambda (p) (proc (car p) (cdr p)))
(try-sort-keys (hash-map ht cons)))]
[(intmap? ht) (intmap-for-each ht proc)]
[(mutable-hash? ht)
(mutable-hash-map ht proc #f)]
[else
;; mutable, impersonated, and weak-equal:
(let loop ([i (hash-iterate-first ht)])
@ -418,6 +420,8 @@
(map (lambda (p) (proc (car p) (cdr p)))
(try-sort-keys (hash-map ht cons)))]
[(intmap? ht) (intmap-map ht proc)]
[(mutable-hash? ht)
(mutable-hash-map ht proc #t)]
[else
;; mutable, impersonated, and weak-equal:
(let loop ([i (hash-iterate-first ht)])
@ -429,6 +433,32 @@
(|#%app| proc key val)))
(loop (hash-iterate-next ht i)))))])]))
(define (mutable-hash-map ht proc map?)
;; Inline iteration over the internal vector to avoid the overhead
;; of calling `hash-iterate-...` for each step
(let vec-loop ([old-n 0] [try? #t])
(let ([vec (prepare-iterate! ht old-n)])
(let loop ([i old-n])
(cond
[(= i (#%vector-length vec))
(if try?
(vec-loop i (> i old-n))
(if map? '() (void)))]
[else
(let ([p (#%vector-ref vec i)])
(let ([key (car p)]
[val (cdr p)])
(cond
[(or (eq? key #!bwp)
(eq? val #!bwp))
(loop (fx+ i 1))]
[map?
(cons (|#%app| proc key val)
(loop (fx+ i 1)))]
[else
(|#%app| proc key val)
(loop (fx+ i 1))])))])))))
;; In sorted hash-table travesals, make some effort to sort the key.
;; This attempt is useful for making hash-table traversals more
;; deterministic, especially for marshaling operations.