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source: branches/f4grobner/pair-queue.lisp@ 4139

Last change on this file since 4139 was 4139, checked in by Marek Rychlik, 8 years ago

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[1201]1;;; -*- Mode: Lisp -*-
[76]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
[449]22(defpackage "PAIR-QUEUE"
[3949]23 (:use :cl :priority-queue :monom :polynomial :symbolic-polynomial :utils)
[3920]24 (:export "CRITICAL-PAIR"
25 "CRITICAL-PAIR-FIRST"
26 "CRITICAL-PAIR-SECOND"
[3948]27 "CRITICAL-PAIR-QUEUE"
[3964]28 "SELECTION-STRATEGY"
[4135]29 "+NORMAL-STRATEGY+"
30 "+MIN-TOTAL-DEGREE-STRATEGY+"
31 "+MIN-COMBINED-LENGTH-STRATEGY+"
[3977]32 "MAKE-CRITICAL-PAIR-QUEUE"
[3918]33 )
34 (:documentation "Critical pair queue implementation. The pair queue is a list of critical
35pairs, ordered by some partial order. Pair queue is a kind of priority queue.")
36 )
[449]37
[450]38(in-package :pair-queue)
39
[3919]40(defclass critical-pair ()
[3921]41 ((first :initform nil :initarg :first :accessor critical-pair-first :type poly)
42 (second :initform nil :initarg :second :accessor critical-pair-second :type poly))
[3930]43 (:documentation "Represents a critical pair, i.e. a pair of two polynomials. The derived
44classes may add extra data used in computing the order of critical pairs."))
[3919]45
[3921]46(defmethod print-object ((self critical-pair) stream)
[3920]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
[3927]54(defclass selection-strategy ()
[4138]55 ((pair-key-fn :initform (error "Initarg :pair-key-fn must be specified.")
[3959]56 :initarg :pair-key-fn
57 :accessor pair-key-fn)
[4138]58 (pair-order-fn :initform (error "Initarg :pair-order-fn must be specified.")
[3959]59 :initarg :pair-order-fn
60 :accessor pair-order-fn))
[4135]61 (:documentation "The two ingredients of a strategy is a function
[3940]62PAIR-KEY-FUNCTION which computes a key from the critical pair, which
63can be any type of data, and a function PAIR-ORDER-FN used to compaire
64the calculated keys to determine which pair is more promising and
[3941]65should be considered first. The normal selection strategy for a given
66monomial order PAIR-ORDER-FN consists in selecting the pair with the
67minimal LCM of leading monomials first."))
[60]68
[3932]69(defmethod print-object ((self selection-strategy) stream)
70 (print-unreadable-object (self stream :type t :identity t)
71 (with-accessors ((pair-key-fn pair-key-fn)
72 (pair-order-fn pair-order-fn))
73 self
74 (format stream "PAIR-KEY-FN=~A PAIR-ORDER-FN=~A"
75 pair-key-fn pair-order-fn))))
76
[4135]77(defparameter +normal-strategy+
78 (make-instance
79 'selection-strategy
80 :pair-key-fn #'(lambda (p q) (universal-lcm (leading-monomial p) (leading-monomial q)))
81 :pair-order-fn #'lex>)
82 "The normal selection strategy where a pair with the largest LCM of
83leading monomials is selected.")
[3932]84
[4135]85(defparameter +min-total-degree-strategy+
86 (make-instance
87 'selection-strategy
88 :pair-key-fn #'(lambda (p q) (total-degree (universal-lcm (leading-monomial p) (leading-monomial q))))
89 :pair-order-fn #'<)
90 "A selection strategy where a pair with a minimum total degree of
91 LCM of leading monomials is selected.")
[3933]92
[4135]93(defparameter +min-combined-length-strategy+
94 (make-instance
95 'selection-strategy
96 :pair-key-fn #'(lambda (p q) (+ (poly-length p) (poly-length q)))
97 :pair-order-fn #'<)
98 "A selection strategy where a pair with the minimum combined length of both
99polynomials is selected.")
[3938]100
[4135]101(defclass critical-pair-queue (priority-queue)
102 ()
103 (:documentation "Implements critical pair priority queue."))
[3944]104
[4139]105(defmethod initialize-instance :after ((self critical-pair-queue) &key strategy poly-list start)
[4135]106 "Allocates a priority queue SELF for critical pairs from strategy SELF."
107 (declare (ignore poly-list start))
108 (with-slots (pair-key-fn pair-order-fn)
109 strategy
110 (reinitialize-instance self
111 :element-type 'critical-pair
112 :element-key #'(lambda (pair) (funcall pair-key-fn
113 (critical-pair-first pair)
114 (critical-pair-second pair)))
115 :test pair-order-fn)))
116
117(defgeneric enqueue-critical-pairs (self &optional poly-list start)
118 (:method ((self critical-pair-queue) &optional (poly-list nil) (start 0))
119 "The argument POLY-LIST should the initial list of
120polynomials. and START is the first position beyond the elements
121which form a partial Grobner basis, i.e. satisfy the Buchberger
122criterion."
123 (let* ((s (1- (length poly-list)))
124 (b (nconc (makelist (make-instance 'critical-pair :first (elt poly-list i) :second (elt poly-list j))
125 (i 0 (1- start)) (j start s))
126 (makelist (make-instance 'critical-pair :first (elt poly-list i) :second (elt poly-list j))
127 (i start (1- s)) (j (1+ i) s)))))
128 (dolist (pair b self)
129 (enqueue self pair)))))
130
131
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