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source: branches/f4grobner/pair-queue.lisp@ 3982

Last change on this file since 3982 was 3977, 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 "MAKE-CRITICAL-PAIR-QUEUE"
32 )
33 (:documentation "Critical pair queue implementation. The pair queue is a list of critical
34pairs, ordered by some partial order. Pair queue is a kind of priority queue.")
35 )
36
37(in-package :pair-queue)
38
39(defclass critical-pair ()
40 ((first :initform nil :initarg :first :accessor critical-pair-first :type poly)
41 (second :initform nil :initarg :second :accessor critical-pair-second :type poly))
42 (:documentation "Represents a critical pair, i.e. a pair of two polynomials. The derived
43classes may add extra data used in computing the order of critical pairs."))
44
45(defmethod print-object ((self critical-pair) stream)
46 (print-unreadable-object (self stream :type t :identity t)
47 (with-accessors ((first critical-pair-first)
48 (second critical-pair-second))
49 self
50 (format stream "FIRST=~A SECOND=~A"
51 first second))))
52
53(defclass selection-strategy ()
54 ((pair-key-fn :initform #'(lambda (p q) (universal-lcm (leading-monomial p) (leading-monomial q)))
55 :initarg :pair-key-fn
56 :accessor pair-key-fn)
57 (pair-order-fn :initform #'lex>
58 :initarg :pair-order-fn
59 :accessor pair-order-fn))
60 (:documentation "Represents the normal critical pair selection
61strategy. The two ingredients of a strategy is a function
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
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."))
68
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
77(defclass min-total-degree-strategy (selection-strategy)
78 ((pair-key-fn :initform #'(lambda (p q) (total-degree (universal-lcm (leading-monomial p) (leading-monomial q)))))
79 (pair-order-fn :initform #'<))
80 (:documentation "Make a selection strategy where a pair with a
81minimum total degree of LCM of leading monomials is selected."))
82
83(defclass min-combined-length-strategy (selection-strategy)
84 ((pair-key-fn :initform #'(lambda (p q) (+ (poly-length p) (poly-length q))))
85 (pair-order-fn :initform #'<))
86 (:documentation "Make a selection strategy where a pair with the minimum combined length of both
87polynomials is selected."))
88
89(defun make-critical-pair-queue (&key pair-key-fn pair-order-fn (poly-list nil) (start 1)
90 &aux (pq (make-priority-queue
91 :element-type 'critical-pair
92 :element-key #'(lambda (pair) (funcall pair-key-fn
93 (critical-pair-first pair)
94 (critical-pair-second pair)))
95 :test pair-order-fn)))
96 "Makes a priority queue for critical pairs. The argument POLY-LIST should 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 ;; Add critical pairs for polynomials in POLY-LIST
100 (let* ((s (1- (length poly-list)))
101 (b (nconc (makelist (make-instance 'critical-pair :first (elt poly-list i) :second (elt poly-list j))
102 (i 0 (1- start)) (j start s))
103 (makelist (make-instance 'critical-pair :first (elt poly-list i) :second (elt poly-list j))
104 (i start (1- s)) (j (1+ i) s)))))
105 (dolist (pair b pq)
106 (priority-queue-insert pq pair))))
107
108
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