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source: branches/f4grobner/priority-queue.lisp@ 845

Last change on this file since 845 was 609, checked in by Marek Rychlik, 9 years ago

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1;;; -*- Mode: Lisp; Package: Maxima; Syntax: Common-Lisp; Base: 10 -*-
2;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;
3;;;
4;;; Copyright (C) 1999, 2002, 2009, 2015 Marek Rychlik <rychlik@u.arizona.edu>
5;;;
6;;; This program is free software; you can redistribute it and/or modify
7;;; it under the terms of the GNU General Public License as published by
8;;; the Free Software Foundation; either version 2 of the License, or
9;;; (at your option) any later version.
10;;;
11;;; This program is distributed in the hope that it will be useful,
12;;; but WITHOUT ANY WARRANTY; without even the implied warranty of
13;;; MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
14;;; GNU General Public License for more details.
15;;;
16;;; You should have received a copy of the GNU General Public License
17;;; along with this program; if not, write to the Free Software
18;;; Foundation, Inc., 59 Temple Place - Suite 330, Boston, MA 02111-1307, USA.
19;;;
20;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;
21
22;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;
23;;
24;; A conventional implementation of priority queues based on heaps
25;;
26;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;
27
28(defpackage "PRIORITY-QUEUE"
29 (:use :cl)
30 (:export "*PRIORITY-QUEUE-ALLOCATION-SIZE*"
31 "PRIORITY-QUEUE"
32 "PRIORITY-QUEUE-HEAP"
33 "PRIORITY-QUEUE-TEST"
34 "MAKE-PRIORITY-QUEUE"
35 "PRIORITY-QUEUE-INSERT"
36 "PRIORITY-QUEUE-REMOVE"
37 "PRIORITY-QUEUE-EMPTY-P"
38 "PRIORITY-QUEUE-SIZE"
39 ))
40
41(in-package :priority-queue)
42(defparameter *priority-queue-allocation-size* 16)
43
44(defun priority-queue-make-heap (&key (element-type 'fixnum))
45 (make-array *priority-queue-allocation-size* :element-type element-type :fill-pointer 1
46 :adjustable t))
47
48(defstruct (priority-queue (:constructor priority-queue-construct))
49 (heap (priority-queue-make-heap))
50 test)
51
52(defun make-priority-queue (&key (element-type 'fixnum)
53 (test #'<=)
54 (element-key #'identity))
55 (priority-queue-construct
56 :heap (priority-queue-make-heap :element-type element-type)
57 :test #'(lambda (x y) (funcall test (funcall element-key y) (funcall element-key x)))))
58
59(defun priority-queue-insert (pq item)
60 (priority-queue-heap-insert (priority-queue-heap pq) item (priority-queue-test pq)))
61
62(defun priority-queue-remove (pq)
63 (priority-queue-heap-remove (priority-queue-heap pq) (priority-queue-test pq)))
64
65(defun priority-queue-empty-p (pq)
66 (priority-queue-heap-empty-p (priority-queue-heap pq)))
67
68(defun priority-queue-size (pq)
69 (fill-pointer (priority-queue-heap pq)))
70
71(defun priority-queue-upheap (a k
72 &optional
73 (test #'<=)
74 &aux (v (aref a k)))
75 (declare (fixnum k))
76 (assert (< 0 k (fill-pointer a)))
77 (loop
78 (let ((parent (ash k -1)))
79 (when (zerop parent) (return))
80 (unless (funcall test (aref a parent) v)
81 (return))
82 (setf (aref a k) (aref a parent)
83 k parent)))
84 (setf (aref a k) v)
85 a)
86
87
88(defun priority-queue-heap-insert (a item &optional (test #'<=))
89 (vector-push-extend item a)
90 (priority-queue-upheap a (1- (fill-pointer a)) test))
91
92(defun priority-queue-downheap (a k
93 &optional
94 (test #'<=)
95 &aux (v (aref a k)) (j 0) (n (fill-pointer a)))
96 (declare (fixnum k n j))
97 (loop
98 (unless (<= k (ash n -1))
99 (return))
100 (setf j (ash k 1))
101 (if (and (< j n) (not (funcall test (aref a (1+ j)) (aref a j))))
102 (incf j))
103 (when (funcall test (aref a j) v)
104 (return))
105 (setf (aref a k) (aref a j)
106 k j))
107 (setf (aref a k) v)
108 a)
109
110(defun priority-queue-heap-remove (a &optional (test #'<=) &aux (v (aref a 1)))
111 (when (<= (fill-pointer a) 1) (error "Empty queue."))
112 (setf (aref a 1) (vector-pop a))
113 (priority-queue-downheap a 1 test)
114 (values v a))
115
116(defun priority-queue-heap-empty-p (a)
117 (<= (fill-pointer a) 1))
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