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source: branches/f4grobner/pair-queue.lisp@ 3927

Last change on this file since 3927 was 3927, 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 "MAKE-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."))
45
46(defmethod print-object ((self critical-pair) stream)
47 (print-unreadable-object (self stream :type t :identity t)
48 (with-accessors ((first critical-pair-first)
49 (second critical-pair-second))
50 self
51 (format stream "FIRST=~A SECOND=~A"
52 first second))))
53
54(defclass selection-strategy ()
55 ((pair-key-fn :initform nil :initarg :pair-key-fn :accessor pair-key-fn)
56 (pair-order-fn :initform nil :initarg :pair-order-fn :accessor pair-order-fn))
57 (:documentation "Sets up variables *PAIR-KEY-FUNCTION* and *PAIR-ORDER* used
58to determine the priority of critical pairs in the priority queue."))
59
60(defclass critical-pair-queue (selection-strategy)
61 ((pq :initform (make-priority-queue
62 :element-type 'critical-pair
63 :element-key #'(lambda (pair) (funcall pair-key-fn (critical-pair-first pair) (critical-pair-second pair)))
64 :test pair-order-fn))))
65
66(defun pair-queue-initialize (pq f start
67 &aux
68 (s (1- (length f)))
69 (b (nconc (makelist (make-instance 'critical-pair :first (elt f i) :second (elt f j))
70 (i 0 (1- start)) (j start s))
71 (makelist (make-instance 'critical-pair :first (elt f i) :second (elt f j))
72 (i start (1- s)) (j (1+ i) s)))))
73 "Initializes the priority for critical pairs. F is the initial list of polynomials.
74START is the first position beyond the elements which form a partial
75grobner basis, i.e. satisfy the Buchberger criterion."
76 (declare (type priority-queue pq) (type fixnum start))
77 (dolist (pair b pq)
78 (priority-queue-insert pq pair)))
79
80(defun pair-queue-insert (b pair)
81 (priority-queue-insert b pair))
82
83(defun pair-queue-remove (b)
84 (priority-queue-remove b))
85
86(defun pair-queue-size (b)
87 (priority-queue-size b))
88
89(defun pair-queue-empty-p (b)
90 (priority-queue-empty-p b))
91
92
93(defun make-normal-strategy (monomial-order-fn)
94 "Make a normal selection strategy for a given monomial order MONOMIAL-ORDER-FN. A pair
95with the minimal LCM of leading monomials is selected."
96 (make-instance 'selection-strategy
97 :pair-key-fn #'(lambda (p q) (universal-lcm (leading-monomial p) (leading-monomial q)))
98 :pair-order-fn monomial-order-fn))
99
100(defun make-min-total-degree-strategy ()
101 "Make a selection strategy where a pair with a minimum total degree of LCM
102of leading monomials is selected."
103 (make-instance 'selection-strategy
104 :pair-key-fn #'(lambda (p q) (total-degree (universal-lcm (leading-monomial p) (leading-monomial q))))
105 :pair-order* #'<))
106
107(defun make-minimal-length-strategy ()
108 "Make a selection strategy where a pair with the minimum combined length of both
109polynomials is selected."
110 (make-instance 'selection-strategy
111 :pair-key-fn #'(lambda (p q) (+ (poly-length p) (poly-length q)))
112 :pair-order #'<))
113
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