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source: branches/f4grobner/pair-queue.lisp@ 3948

Last change on this file since 3948 was 3948, 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 :utils)
24 (:export "CRITICAL-PAIR"
25 "CRITICAL-PAIR-FIRST"
26 "CRITICAL-PAIR-SECOND"
27 "CRITICAL-PAIR-QUEUE"
28 "PAIR-QUEUE-INITIALIZE"
29 "PAIR-QUEUE-INSERT"
30 "PAIR-QUEUE-REMOVE"
31 "PAIR-QUEUE-SIZE"
32 "PAIR-QUEUE-EMPTY-P"
33 "SET-PAIR-HEURISTIC"
34 )
35 (:documentation "Critical pair queue implementation. The pair queue is a list of critical
36pairs, ordered by some partial order. Pair queue is a kind of priority queue.")
37 )
38
39(in-package :pair-queue)
40
41(defclass critical-pair ()
42 ((first :initform nil :initarg :first :accessor critical-pair-first :type poly)
43 (second :initform nil :initarg :second :accessor critical-pair-second :type poly))
44 (:documentation "Represents a critical pair, i.e. a pair of two polynomials. The derived
45classes may add extra data used in computing the order of critical pairs."))
46
47(defmethod print-object ((self critical-pair) stream)
48 (print-unreadable-object (self stream :type t :identity t)
49 (with-accessors ((first critical-pair-first)
50 (second critical-pair-second))
51 self
52 (format stream "FIRST=~A SECOND=~A"
53 first second))))
54
55(defclass selection-strategy ()
56 ((pair-key-fn :initform #'(lambda (p q) (universal-lcm (leading-monomial p) (leading-monomial q))) :initarg :pair-key-fn :accessor pair-key-fn)
57 (pair-order-fn :initform #'lex> :initarg :pair-order-fn :accessor pair-order-fn))
58 (:documentation "Represents the normal critical pair selection
59strategy. The two ingredients of a strategy is a function
60PAIR-KEY-FUNCTION which computes a key from the critical pair, which
61can be any type of data, and a function PAIR-ORDER-FN used to compaire
62the calculated keys to determine which pair is more promising and
63should be considered first. The normal selection strategy for a given
64monomial order PAIR-ORDER-FN consists in selecting the pair with the
65minimal LCM of leading monomials first."))
66
67(defmethod print-object ((self selection-strategy) stream)
68 (print-unreadable-object (self stream :type t :identity t)
69 (with-accessors ((pair-key-fn pair-key-fn)
70 (pair-order-fn pair-order-fn))
71 self
72 (format stream "PAIR-KEY-FN=~A PAIR-ORDER-FN=~A"
73 pair-key-fn pair-order-fn))))
74
75(defclass min-total-degree-strategy (selection-strategy)
76 ((pair-key-fn :initform #'(lambda (p q) (total-degree (universal-lcm (leading-monomial p) (leading-monomial q)))))
77 (pair-order-fn :initform #'<))
78 (:documentation "Make a selection strategy where a pair with a
79minimum total degree of LCM of leading monomials is selected."))
80
81(defclass minimal-length-strategy (selection-strategy)
82 ((pair-key-fn :initform #'(lambda (p q) (+ (poly-length p) (poly-length q))))
83 (pair-order-fn :initform #'<))
84 (:documentation "Make a selection strategy where a pair with the minimum combined length of both
85polynomials is selected."))
86
87(defclass critical-pair-queue (selection-strategy)
88 ((pq :initform nil :initarg :pq :accessor pq :type priority-queue)))
89
90(defmethod initialize-instance :after ((self critical-pair-queue) &key (f nil) (start 1))
91 "Initializes the priority for critical pairs. F is the initial list of polynomials.
92START is the first position beyond the elements which form a partial
93grobner basis, i.e. satisfy the Buchberger criterion."
94 (with-accessors ((pair-key-fn pair-key-fn)
95 (pair-order-fn pair-order-fn)
96 (pq pq))
97 self
98 (setf pq (make-priority-queue
99 :element-type 'critical-pair
100 :element-key #'(lambda (pair) (funcall pair-key-fn (critical-pair-first pair) (critical-pair-second pair)))
101 :test pair-order-fn))
102 (let* ((s (1- (length f)))
103 (b (nconc (makelist (make-instance 'critical-pair :first (elt f i) :second (elt f j))
104 (i 0 (1- start)) (j start s))
105 (makelist (make-instance 'critical-pair :first (elt f i) :second (elt f j))
106 (i start (1- s)) (j (1+ i) s)))))
107 (dolist (pair b pq)
108 (priority-queue-insert pq pair)))
109 ))
110
111(defmethod print-object ((self critical-pair-queue) stream)
112 (print-unreadable-object (self stream :type t :identity t)
113 (with-accessors ((pair-key-fn pair-key-fn)
114 (pair-order-fn pair-order-fn)
115 (pq pq))
116 self
117 (format stream "PAIR-KEY-FN=~A PAIR-ORDER-FN=~A PQ=~A"
118 pair-key-fn pair-order-fn pq))))
119
120
121(defun pair-queue-initialize (pq f start
122 &aux
123 (s (1- (length f)))
124 (b (nconc (makelist (make-instance 'critical-pair :first (elt f i) :second (elt f j))
125 (i 0 (1- start)) (j start s))
126 (makelist (make-instance 'critical-pair :first (elt f i) :second (elt f j))
127 (i start (1- s)) (j (1+ i) s)))))
128 "Initializes the priority for critical pairs. F is the initial list of polynomials.
129START is the first position beyond the elements which form a partial
130grobner basis, i.e. satisfy the Buchberger criterion."
131 (declare (type priority-queue pq) (type fixnum start))
132 (dolist (pair b pq)
133 (priority-queue-insert pq pair)))
134
135(defun pair-queue-insert (b pair)
136 (priority-queue-insert b pair))
137
138(defun pair-queue-remove (b)
139 (priority-queue-remove b))
140
141(defun pair-queue-size (b)
142 (priority-queue-size b))
143
144(defun pair-queue-empty-p (b)
145 (priority-queue-empty-p b))
146
147
148
149
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