/usr/share/guile/1.8/oop/goops/dispatch.scm is in guile-1.8-libs 1.8.8+1-6ubuntu2.
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;;;;
;;;; This library is free software; you can redistribute it and/or
;;;; modify it under the terms of the GNU Lesser General Public
;;;; License as published by the Free Software Foundation; either
;;;; version 2.1 of the License, or (at your option) any later version.
;;;;
;;;; This library is distributed in the hope that it will be useful,
;;;; but WITHOUT ANY WARRANTY; without even the implied warranty of
;;;; MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU
;;;; Lesser General Public License for more details.
;;;;
;;;; You should have received a copy of the GNU Lesser General Public
;;;; License along with this library; if not, write to the Free Software
;;;; Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301 USA
;;;;
(define-module (oop goops dispatch)
:use-module (oop goops)
:use-module (oop goops util)
:use-module (oop goops compile)
:export (memoize-method!)
:no-backtrace
)
;;;
;;; This file implements method memoization. It will finally be
;;; implemented on C level in order to obtain fast generic function
;;; application also during the first pass through the code.
;;;
;;;
;;; Constants
;;;
(define hashsets 8)
(define hashset-index 6)
(define hash-threshold 3)
(define initial-hash-size 4) ;must be a power of 2 and >= hash-threshold
(define initial-hash-size-1 (- initial-hash-size 1))
(define the-list-of-no-method '(no-method))
;;;
;;; Method cache
;;;
;; (#@dispatch args N-SPECIALIZED #((TYPE1 ... ENV FORMALS FORM1 ...) ...) GF)
;; (#@dispatch args N-SPECIALIZED HASHSET MASK
;; #((TYPE1 ... ENV FORMALS FORM1 ...) ...)
;; GF)
;;; Representation
;; non-hashed form
(define method-cache-entries cadddr)
(define (set-method-cache-entries! mcache entries)
(set-car! (cdddr mcache) entries))
(define (method-cache-n-methods exp)
(n-cache-methods (method-cache-entries exp)))
(define (method-cache-methods exp)
(cache-methods (method-cache-entries exp)))
;; hashed form
(define (set-hashed-method-cache-hashset! exp hashset)
(set-car! (cdddr exp) hashset))
(define (set-hashed-method-cache-mask! exp mask)
(set-car! (cddddr exp) mask))
(define (hashed-method-cache-entries exp)
(list-ref exp 5))
(define (set-hashed-method-cache-entries! exp entries)
(set-car! (list-cdr-ref exp 5) entries))
;; either form
(define (method-cache-generic-function exp)
(list-ref exp (if (method-cache-hashed? exp) 6 4)))
;;; Predicates
(define (method-cache-hashed? x)
(integer? (cadddr x)))
(define max-non-hashed-index (- hash-threshold 2))
(define (passed-hash-threshold? exp)
(and (> (vector-length (method-cache-entries exp)) max-non-hashed-index)
(struct? (car (vector-ref (method-cache-entries exp)
max-non-hashed-index)))))
;;; Converting a method cache to hashed form
(define (method-cache->hashed! exp)
(set-cdr! (cddr exp) (cons 0 (cons initial-hash-size-1 (cdddr exp))))
exp)
;;;
;;; Cache entries
;;;
(define (n-cache-methods entries)
(do ((i (- (vector-length entries) 1) (- i 1)))
((or (< i 0) (struct? (car (vector-ref entries i))))
(+ i 1))))
(define (cache-methods entries)
(do ((i (- (vector-length entries) 1) (- i 1))
(methods '() (let ((entry (vector-ref entries i)))
(if (struct? (car entry))
(cons entry methods)
methods))))
((< i 0) methods)))
;;;
;;; Method insertion
;;;
(define (method-cache-insert! exp entry)
(let* ((entries (method-cache-entries exp))
(n (n-cache-methods entries)))
(if (>= n (vector-length entries))
;; grow cache
(let ((new-entries (make-vector (* 2 (vector-length entries))
the-list-of-no-method)))
(do ((i 0 (+ i 1)))
((= i n))
(vector-set! new-entries i (vector-ref entries i)))
(vector-set! new-entries n entry)
(set-method-cache-entries! exp new-entries))
(vector-set! entries n entry))))
(define (hashed-method-cache-insert! exp entry)
(let* ((cache (hashed-method-cache-entries exp))
(size (vector-length cache)))
(let* ((entries (cons entry (cache-methods cache)))
(size (if (<= (length entries) size)
size
;; larger size required
(let ((new-size (* 2 size)))
(set-hashed-method-cache-mask! exp (- new-size 1))
new-size)))
(min-misses size)
(best #f))
(do ((hashset 0 (+ 1 hashset)))
((= hashset hashsets))
(let* ((test-cache (make-vector size the-list-of-no-method))
(misses (cache-try-hash! min-misses hashset test-cache entries)))
(cond ((zero? misses)
(set! min-misses 0)
(set! best hashset)
(set! cache test-cache)
(set! hashset (- hashsets 1)))
((< misses min-misses)
(set! min-misses misses)
(set! best hashset)
(set! cache test-cache)))))
(set-hashed-method-cache-hashset! exp best)
(set-hashed-method-cache-entries! exp cache))))
;;;
;;; Caching
;;;
(define (cache-hashval hashset entry)
(let ((hashset-index (+ hashset-index hashset)))
(do ((sum 0)
(classes entry (cdr classes)))
((not (struct? (car classes))) sum)
(set! sum (+ sum (struct-ref (car classes) hashset-index))))))
(define (cache-try-hash! min-misses hashset cache entries)
(let ((max-misses 0)
(mask (- (vector-length cache) 1)))
(catch 'misses
(lambda ()
(do ((ls entries (cdr ls))
(misses 0 0))
((null? ls) max-misses)
(do ((i (logand mask (cache-hashval hashset (car ls)))
(logand mask (+ i 1))))
((not (struct? (car (vector-ref cache i))))
(vector-set! cache i (car ls)))
(set! misses (+ 1 misses))
(if (>= misses min-misses)
(throw 'misses misses)))
(if (> misses max-misses)
(set! max-misses misses))))
(lambda (key misses)
misses))))
;;;
;;; Memoization
;;;
;; Backward compatibility
(if (not (defined? 'lookup-create-cmethod))
(define (lookup-create-cmethod gf args)
(no-applicable-method (car args) (cadr args))))
(define (memoize-method! gf args exp)
(if (not (slot-ref gf 'used-by))
(slot-set! gf 'used-by '()))
(let ((applicable ((if (eq? gf compute-applicable-methods)
%compute-applicable-methods
compute-applicable-methods)
gf args)))
(cond (applicable
;; *fixme* dispatch.scm needs rewriting Since the current
;; code mutates the method cache, we have to work on a
;; copy. Otherwise we might disturb another thread
;; currently dispatching on the cache. (No need to copy
;; the vector.)
(let* ((new (list-copy exp))
(res
(cond ((method-cache-hashed? new)
(method-cache-install! hashed-method-cache-insert!
new args applicable))
((passed-hash-threshold? new)
(method-cache-install! hashed-method-cache-insert!
(method-cache->hashed! new)
args
applicable))
(else
(method-cache-install! method-cache-insert!
new args applicable)))))
(set-cdr! (cdr exp) (cddr new))
res))
((null? args)
(lookup-create-cmethod no-applicable-method (list gf '())))
(else
;; Mutate arglist to fit no-applicable-method
(set-cdr! args (list (cons (car args) (cdr args))))
(set-car! args gf)
(lookup-create-cmethod no-applicable-method args)))))
(set-procedure-property! memoize-method! 'system-procedure #t)
(define method-cache-install!
(letrec ((first-n
(lambda (ls n)
(if (or (zero? n) (null? ls))
'()
(cons (car ls) (first-n (cdr ls) (- n 1)))))))
(lambda (insert! exp args applicable)
(let* ((specializers (method-specializers (car applicable)))
(n-specializers
(if (list? specializers)
(length specializers)
(+ 1 (slot-ref (method-cache-generic-function exp)
'n-specialized)))))
(let* ((types (map class-of (first-n args n-specializers)))
(entry+cmethod (compute-entry-with-cmethod applicable types)))
(insert! exp (car entry+cmethod)) ; entry = types + cmethod
(cdr entry+cmethod) ; cmethod
)))))
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