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source: branches/f4grobner/pair-queue.lisp@ 3969

Last change on this file since 3969 was 3967, checked in by Marek Rychlik, 8 years ago

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1;;; -*- Mode: Lisp -*-
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(defpackage "PAIR-QUEUE"
23 (:use :cl :priority-queue :monom :polynomial :symbolic-polynomial :utils)
24 (:export "CRITICAL-PAIR"
25 "CRITICAL-PAIR-FIRST"
26 "CRITICAL-PAIR-SECOND"
27 "CRITICAL-PAIR-QUEUE"
28 "SELECTION-STRATEGY"
29 "MIN-TOTAL-DEGREE-STRATEGY"
30 "MIN-COMBINED-LENGTH-STRATEGY"
31 "ENQUEUE"
32 "DEQUEUE"
33 "QUEUE-SIZE"
34 "QUEUE-EMPTY-P"
35 )
36 (:documentation "Critical pair queue implementation. The pair queue is a list of critical
37pairs, ordered by some partial order. Pair queue is a kind of priority queue.")
38 )
39
40(in-package :pair-queue)
41
42(defclass critical-pair ()
43 ((first :initform nil :initarg :first :accessor critical-pair-first :type poly)
44 (second :initform nil :initarg :second :accessor critical-pair-second :type poly))
45 (:documentation "Represents a critical pair, i.e. a pair of two polynomials. The derived
46classes may add extra data used in computing the order of critical pairs."))
47
48(defmethod print-object ((self critical-pair) stream)
49 (print-unreadable-object (self stream :type t :identity t)
50 (with-accessors ((first critical-pair-first)
51 (second critical-pair-second))
52 self
53 (format stream "FIRST=~A SECOND=~A"
54 first second))))
55
56(defclass selection-strategy ()
57 ((pair-key-fn :initform #'(lambda (p q) (universal-lcm (leading-monomial p) (leading-monomial q)))
58 :initarg :pair-key-fn
59 :accessor pair-key-fn)
60 (pair-order-fn :initform #'lex>
61 :initarg :pair-order-fn
62 :accessor pair-order-fn))
63 (:documentation "Represents the normal critical pair selection
64strategy. The two ingredients of a strategy is a function
65PAIR-KEY-FUNCTION which computes a key from the critical pair, which
66can be any type of data, and a function PAIR-ORDER-FN used to compaire
67the calculated keys to determine which pair is more promising and
68should be considered first. The normal selection strategy for a given
69monomial order PAIR-ORDER-FN consists in selecting the pair with the
70minimal LCM of leading monomials first."))
71
72(defmethod print-object ((self selection-strategy) stream)
73 (print-unreadable-object (self stream :type t :identity t)
74 (with-accessors ((pair-key-fn pair-key-fn)
75 (pair-order-fn pair-order-fn))
76 self
77 (format stream "PAIR-KEY-FN=~A PAIR-ORDER-FN=~A"
78 pair-key-fn pair-order-fn))))
79
80(defclass min-total-degree-strategy (selection-strategy)
81 ((pair-key-fn :initform #'(lambda (p q) (total-degree (universal-lcm (leading-monomial p) (leading-monomial q)))))
82 (pair-order-fn :initform #'<))
83 (:documentation "Make a selection strategy where a pair with a
84minimum total degree of LCM of leading monomials is selected."))
85
86(defclass min-combined-length-strategy (selection-strategy)
87 ((pair-key-fn :initform #'(lambda (p q) (+ (poly-length p) (poly-length q))))
88 (pair-order-fn :initform #'<))
89 (:documentation "Make a selection strategy where a pair with the minimum combined length of both
90polynomials is selected."))
91
92(defclass critical-pair-queue (selection-strategy)
93 ((pq :initform nil :initarg :pq :accessor pq :type priority-queue)))
94
95(defmethod initialize-instance :after ((self critical-pair-queue) &key (poly-list nil) (start 1))
96 "Initializes the priority queue SELF of critical pairs, where POLY-LIST is the initial list of polynomials.
97and START is the first position beyond the elements which form a
98partial Grobner basis, i.e. satisfy the Buchberger criterion."
99 (with-accessors ((pair-key-fn pair-key-fn)
100 (pair-order-fn pair-order-fn)
101 (pq pq))
102 self
103 (setf pq (make-priority-queue
104 :element-type 'critical-pair
105 :element-key #'(lambda (pair) (funcall pair-key-fn (critical-pair-first pair) (critical-pair-second pair)))
106 :test pair-order-fn))
107 ;; Add critical pairs for polynomials in POLY-LIST
108 (let* ((s (1- (length poly-list)))
109 (b (nconc (makelist (make-instance 'critical-pair :first (elt poly-list i) :second (elt poly-list j))
110 (i 0 (1- start)) (j start s))
111 (makelist (make-instance 'critical-pair :first (elt poly-list i) :second (elt poly-list j))
112 (i start (1- s)) (j (1+ i) s)))))
113 (dolist (pair b)
114 (priority-queue-insert pq pair)))))
115
116(defmethod print-object ((self critical-pair-queue) stream)
117 (print-unreadable-object (self stream :type t :identity t)
118 (with-accessors ((pair-key-fn pair-key-fn)
119 (pair-order-fn pair-order-fn)
120 (pq pq))
121 self
122 (format stream "PAIR-KEY-FN=~A PAIR-ORDER-FN=~A PQ=~A"
123 pair-key-fn pair-order-fn pq))))
124
125
126
127(defgeneric enqueue (self object)
128 (:documentation "Insert an object OBJECT into a queue SELF.")
129 (:method ((self critical-pair-queue) (pair critical-pair))
130 (with-slots (pq)
131 self
132 (priority-queue-insert pq pair))))
133
134(defgeneric dequeue (self)
135 (:documentation "Remove an object from a queue SELF. Returns the removed object.")
136 (:method ((self critical-pair-queue))
137 (with-slots (pq)
138 self
139 (priority-queue-remove pq))))
140
141(defgeneric queue-size (self)
142 (:documentation "Returns the number of elements in the queue SELF.")
143 (:method ((self critical-pair-queue))
144 (with-slots (pq)
145 self
146 (priority-queue-size pq))))
147
148(defgeneric queue-empty-p (self)
149 (:documentation "Returns T if the queue SELF is empty, NIL otherwise.")
150 (:method ((self critical-pair-queue))
151 (with-slots (pq)
152 self
153 (priority-queue-empty-p pq))))
154
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