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294 lines
9.1 KiB
Scheme
294 lines
9.1 KiB
Scheme
;;;; Copyright (C) 1999, 2000 Free Software Foundation, Inc.
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;;;;
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;;;; This program is free software; you can redistribute it and/or modify
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;;;; it under the terms of the GNU General Public License as published by
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;;;; the Free Software Foundation; either version 2, or (at your option)
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;;;; any later version.
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;;;;
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;;;; This program is distributed in the hope that it will be useful,
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;;;; but WITHOUT ANY WARRANTY; without even the implied warranty of
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;;;; MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
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;;;; GNU General Public License for more details.
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;;;;
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;;;; You should have received a copy of the GNU General Public License
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;;;; along with this software; see the file COPYING. If not, write to
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;;;; the Free Software Foundation, Inc., 59 Temple Place, Suite 330,
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;;;; Boston, MA 02111-1307 USA
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;;;;
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;;;; As a special exception, the Free Software Foundation gives permission
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;;;; for additional uses of the text contained in its release of GUILE.
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;;;;
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;;;; The exception is that, if you link the GUILE library with other files
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;;;; to produce an executable, this does not by itself cause the
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;;;; resulting executable to be covered by the GNU General Public License.
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;;;; Your use of that executable is in no way restricted on account of
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;;;; linking the GUILE library code into it.
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;;;;
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;;;; This exception does not however invalidate any other reasons why
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;;;; the executable file might be covered by the GNU General Public License.
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;;;;
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;;;; This exception applies only to the code released by the
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;;;; Free Software Foundation under the name GUILE. If you copy
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;;;; code from other Free Software Foundation releases into a copy of
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;;;; GUILE, as the General Public License permits, the exception does
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;;;; not apply to the code that you add in this way. To avoid misleading
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;;;; anyone as to the status of such modified files, you must delete
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;;;; this exception notice from them.
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;;;;
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;;;; If you write modifications of your own for GUILE, it is your choice
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;;;; whether to permit this exception to apply to your modifications.
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;;;; If you do not wish that, delete this exception notice.
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;;;;
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(define-module (oop goops dispatch)
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:use-module (oop goops)
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:use-module (oop goops util)
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:use-module (oop goops compile)
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:no-backtrace
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)
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(export memoize-method!)
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;;;
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;;; This file implements method memoization. It will finally be
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;;; implemented on C level in order to obtain fast generic function
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;;; application also during the first pass through the code.
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;;;
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;;;
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;;; Constants
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;;;
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(define hashsets 8)
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(define hashset-index 6)
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(define hash-threshold 3)
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(define initial-hash-size 4) ;must be a power of 2 and >= hash-threshold
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(define initial-hash-size-1 (- initial-hash-size 1))
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(define the-list-of-no-method '(no-method))
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;;;
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;;; Method cache
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;;;
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;; (#@dispatch args N-SPECIALIZED #((TYPE1 ... ENV FORMALS FORM1 ...) ...) GF)
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;; (#@dispatch args N-SPECIALIZED HASHSET MASK
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;; #((TYPE1 ... ENV FORMALS FORM1 ...) ...)
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;; GF)
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;;; Representation
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;; non-hashed form
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(define method-cache-entries cadddr)
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(define (set-method-cache-entries! mcache entries)
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(set-car! (cdddr mcache) entries))
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(define (method-cache-n-methods exp)
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(n-cache-methods (method-cache-entries exp)))
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(define (method-cache-methods exp)
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(cache-methods (method-cache-entries exp)))
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;; hashed form
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(define (set-hashed-method-cache-hashset! exp hashset)
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(set-car! (cdddr exp) hashset))
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(define (set-hashed-method-cache-mask! exp mask)
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(set-car! (cddddr exp) mask))
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(define (hashed-method-cache-entries exp)
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(list-ref exp 5))
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(define (set-hashed-method-cache-entries! exp entries)
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(set-car! (list-cdr-ref exp 5) entries))
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;; either form
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(define (method-cache-generic-function exp)
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(list-ref exp (if (method-cache-hashed? exp) 6 4)))
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;;; Predicates
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(define (method-cache-hashed? x)
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(integer? (cadddr x)))
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(define max-non-hashed-index (- hash-threshold 2))
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(define (passed-hash-threshold? exp)
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(and (> (vector-length (method-cache-entries exp)) max-non-hashed-index)
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(struct? (car (vector-ref (method-cache-entries exp)
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max-non-hashed-index)))))
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;;; Converting a method cache to hashed form
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(define (method-cache->hashed! exp)
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(set-cdr! (cddr exp) (cons 0 (cons initial-hash-size-1 (cdddr exp))))
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exp)
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;;;
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;;; Cache entries
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;;;
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(define (n-cache-methods entries)
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(do ((i (- (vector-length entries) 1) (- i 1)))
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((or (< i 0) (struct? (car (vector-ref entries i))))
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(+ i 1))))
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(define (cache-methods entries)
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(do ((i (- (vector-length entries) 1) (- i 1))
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(methods '() (let ((entry (vector-ref entries i)))
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(if (struct? (car entry))
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(cons entry methods)
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methods))))
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((< i 0) methods)))
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;;;
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;;; Method insertion
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;;;
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(define (method-cache-insert! exp entry)
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(let* ((entries (method-cache-entries exp))
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(n (n-cache-methods entries)))
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(if (>= n (vector-length entries))
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;; grow cache
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(let ((new-entries (make-vector (* 2 (vector-length entries))
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the-list-of-no-method)))
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(do ((i 0 (+ i 1)))
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((= i n))
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(vector-set! new-entries i (vector-ref entries i)))
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(vector-set! new-entries n entry)
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(set-method-cache-entries! exp new-entries))
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(vector-set! entries n entry))))
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(define (hashed-method-cache-insert! exp entry)
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(let* ((cache (hashed-method-cache-entries exp))
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(size (vector-length cache)))
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(let* ((entries (cons entry (cache-methods cache)))
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(size (if (<= (length entries) size)
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size
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;; larger size required
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(let ((new-size (* 2 size)))
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(set-hashed-method-cache-mask! exp (- new-size 1))
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new-size)))
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(min-misses size)
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(best #f))
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(do ((hashset 0 (+ 1 hashset)))
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((= hashset hashsets))
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(let* ((test-cache (make-vector size the-list-of-no-method))
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(misses (cache-try-hash! min-misses hashset test-cache entries)))
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(cond ((zero? misses)
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(set! min-misses 0)
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(set! best hashset)
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(set! cache test-cache)
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(set! hashset (- hashsets 1)))
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((< misses min-misses)
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(set! min-misses misses)
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(set! best hashset)
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(set! cache test-cache)))))
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(set-hashed-method-cache-hashset! exp best)
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(set-hashed-method-cache-entries! exp cache))))
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;;;
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;;; Caching
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;;;
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(define environment? pair?)
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(define (cache-hashval hashset entry)
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(let ((hashset-index (+ hashset-index hashset)))
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(do ((sum 0)
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(classes entry (cdr classes)))
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((environment? (car classes)) sum)
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(set! sum (+ sum (struct-ref (car classes) hashset-index))))))
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(define (cache-try-hash! min-misses hashset cache entries)
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(let ((max-misses 0)
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(mask (- (vector-length cache) 1)))
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(catch 'misses
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(lambda ()
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(do ((ls entries (cdr ls))
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(misses 0 0))
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((null? ls) max-misses)
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(do ((i (logand mask (cache-hashval hashset (car ls)))
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(logand mask (+ i 1))))
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((not (struct? (car (vector-ref cache i))))
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(vector-set! cache i (car ls)))
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(set! misses (+ 1 misses))
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(if (>= misses min-misses)
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(throw 'misses misses)))
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(if (> misses max-misses)
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(set! max-misses misses))))
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(lambda (key misses)
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misses))))
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;;;
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;;; Memoization
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;;;
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;; Backward compatibility
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(if (not (defined? 'lookup-create-cmethod))
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(define (lookup-create-cmethod gf args)
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(no-applicable-method (car args) (cadr args))))
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(define (memoize-method! gf args exp)
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(if (not (slot-ref gf 'used-by))
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(slot-set! gf 'used-by '()))
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(let ((applicable ((if (eq? gf compute-applicable-methods)
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%compute-applicable-methods
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compute-applicable-methods)
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gf args)))
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(cond (applicable
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;; *fixme* dispatch.scm needs rewriting Since the current
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;; code mutates the method cache, we have to work on a
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;; copy. Otherwise we might disturb another thread
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;; currently dispatching on the cache. (No need to copy
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;; the vector.)
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(let* ((new (list-copy exp))
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(res
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(cond ((method-cache-hashed? new)
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(method-cache-install! hashed-method-cache-insert!
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new args applicable))
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((passed-hash-threshold? new)
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(method-cache-install! hashed-method-cache-insert!
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(method-cache->hashed! new)
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args
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applicable))
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(else
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(method-cache-install! method-cache-insert!
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new args applicable)))))
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(set-cdr! (cdr exp) (cddr new))
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res))
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((null? args)
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(lookup-create-cmethod no-applicable-method (list gf '())))
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(else
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;; Mutate arglist to fit no-applicable-method
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(set-cdr! args (list (cons (car args) (cdr args))))
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(set-car! args gf)
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(lookup-create-cmethod no-applicable-method args)))))
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(set-procedure-property! memoize-method! 'system-procedure #t)
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(define method-cache-install!
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(letrec ((first-n
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(lambda (ls n)
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(if (or (zero? n) (null? ls))
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'()
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(cons (car ls) (first-n (cdr ls) (- n 1)))))))
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(lambda (insert! exp args applicable)
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(let* ((specializers (method-specializers (car applicable)))
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(n-specializers
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(if (list? specializers)
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(length specializers)
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(+ 1 (slot-ref (method-cache-generic-function exp)
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'n-specialized)))))
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(let* ((types (map class-of (first-n args n-specializers)))
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(entry+cmethod (compute-entry-with-cmethod applicable types)))
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(insert! exp (car entry+cmethod)) ; entry = types + cmethod
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(cdr entry+cmethod) ; cmethod
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)))))
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