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source: branches/f4grobner/order.lisp@ 448

Last change on this file since 448 was 444, checked in by Marek Rychlik, 9 years ago

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[80]1;;; -*- Mode: Lisp; Package: Maxima; Syntax: Common-Lisp; Base: 10 -*-
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
[444]22;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;
23;;
24;; Implementations of various admissible monomial orders
25;;
26;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;
27
[412]28(defpackage "ORDER"
29 (:use :cl :monomial)
30 (:export "LEX>"
31 "GRLEX>"
32 "REVLEX>"
33 "GREVLEX>"
[440]34 "INVLEX>"
35 "MONOMIAL-ORDER"
36 "REVERSE-MONOMIAL-ORDER"
37 "*PRIMARY-ELIMINATION-ORDER*"
38 "*SECONDARY-ELIMINATION-ORDER*"
39 "*ELIMINATION-ORDER*"
40 "ELIMINATION-ORDER"
41 "ELIMINATION-ORDER-1"))
[80]42
[417]43(in-package :order)
44
[49]45;; pure lexicographic
46(defun lex> (p q &optional (start 0) (end (monom-dimension p)))
47 "Return T if P>Q with respect to lexicographic order, otherwise NIL.
48The second returned value is T if P=Q, otherwise it is NIL."
49 (declare (type monom p q) (type fixnum start end))
50 (do ((i start (1+ i)))
51 ((>= i end) (values nil t))
52 (declare (type fixnum i))
53 (cond
54 ((> (monom-elt p i) (monom-elt q i))
55 (return-from lex> (values t nil)))
56 ((< (monom-elt p i) (monom-elt q i))
57 (return-from lex> (values nil nil))))))
58
59;; total degree order , ties broken by lexicographic
60(defun grlex> (p q &optional (start 0) (end (monom-dimension p)))
61 "Return T if P>Q with respect to graded lexicographic order, otherwise NIL.
62The second returned value is T if P=Q, otherwise it is NIL."
63 (declare (type monom p q) (type fixnum start end))
64 (let ((d1 (monom-total-degree p start end))
65 (d2 (monom-total-degree q start end)))
66 (cond
67 ((> d1 d2) (values t nil))
68 ((< d1 d2) (values nil nil))
69 (t
70 (lex> p q start end)))))
71
72
73;; reverse lexicographic
74(defun revlex> (p q &optional (start 0) (end (monom-dimension p)))
75 "Return T if P>Q with respect to reverse lexicographic order, NIL
76otherwise. The second returned value is T if P=Q, otherwise it is
77NIL. This is not and admissible monomial order because some sets do
78not have a minimal element. This order is useful in constructing other
79orders."
80 (declare (type monom p q) (type fixnum start end))
81 (do ((i (1- end) (1- i)))
82 ((< i start) (values nil t))
83 (declare (type fixnum i))
84 (cond
85 ((< (monom-elt p i) (monom-elt q i))
86 (return-from revlex> (values t nil)))
87 ((> (monom-elt p i) (monom-elt q i))
88 (return-from revlex> (values nil nil))))))
89
90
[426]91;; total degree, ties broken by reverse lexicographic
92(defun grevlex> (p q &optional (start 0) (end (monom-dimension p)))
93 "Return T if P>Q with respect to graded reverse lexicographic order,
94NIL otherwise. The second returned value is T if P=Q, otherwise it is NIL."
95 (declare (type monom p q) (type fixnum start end))
96 (let ((d1 (monom-total-degree p start end))
97 (d2 (monom-total-degree q start end)))
98 (cond
99 ((> d1 d2) (values t nil))
100 ((< d1 d2) (values nil nil))
101 (t
102 (revlex> p q start end)))))
103
[49]104(defun invlex> (p q &optional (start 0) (end (monom-dimension p)))
105 "Return T if P>Q with respect to inverse lexicographic order, NIL otherwise
106The second returned value is T if P=Q, otherwise it is NIL."
107 (declare (type monom p q) (type fixnum start end))
108 (do ((i (1- end) (1- i)))
109 ((< i start) (values nil t))
110 (declare (type fixnum i))
111 (cond
112 ((> (monom-elt p i) (monom-elt q i))
113 (return-from invlex> (values t nil)))
114 ((< (monom-elt p i) (monom-elt q i))
115 (return-from invlex> (values nil nil))))))
[439]116
117;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;
118;;
119;; Some globally-defined variables holding monomial orders
120;; and related macros/functions.
121;;
122;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;
123
124(defvar *monomial-order* #'lex>
125 "Default order for monomial comparisons. This global variable holds
126the order which is in effect when performing polynomial
127arithmetic. The global order is called by the macro MONOMIAL-ORDER,
128which is somewhat more elegant than FUNCALL.")
129
130(defmacro monomial-order (x y)
131 "Calls the global monomial order function, held by *MONOMIAL-ORDER*."
132 `(funcall *monomial-order* ,x ,y))
133
134(defmacro reverse-monomial-order (x y)
135 "Calls the inverse monomial order to the global monomial order function,
136held by *MONOMIAL-ORDER*."
137 `(monomial-order ,y ,x))
138
139(defvar *primary-elimination-order* #'lex>)
140
141(defvar *secondary-elimination-order* #'lex>)
142
143(defvar *elimination-order* nil
144 "Default elimination order used in elimination-based functions.
145If not NIL, it is assumed to be a proper elimination order. If NIL,
146we will construct an elimination order using the values of
147*PRIMARY-ELIMINATION-ORDER* and *SECONDARY-ELIMINATION-ORDER*.")
148
149;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;
150;;
151;; Order making functions
152;;
153;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;
154
155(defun elimination-order (k)
156 "Return a predicate which compares monomials according to the
157K-th elimination order. Two variables *PRIMARY-ELIMINATION-ORDER*
158and *SECONDARY-ELIMINATION-ORDER* control the behavior on the first K
159and the remaining variables, respectively."
160 (declare (type fixnum k))
161 #'(lambda (p q &optional (start 0) (end (monom-dimension p)))
162 (declare (type monom p q) (type fixnum start end))
163 (multiple-value-bind (primary equal)
164 (funcall *primary-elimination-order* p q start k)
165 (if equal
166 (funcall *secondary-elimination-order* p q k end)
167 (values primary nil)))))
168
169(defun elimination-order-1 (p q &optional (start 0) (end (monom-dimension p)))
170 "Equivalent to the function returned by the call to (ELIMINATION-ORDER 1)."
171 (declare (type monom p q) (type fixnum start end))
172 (cond
173 ((> (monom-elt p start) (monom-elt q start)) (values t nil))
174 ((< (monom-elt p start) (monom-elt q start)) (values nil nil))
175 (t (funcall *secondary-elimination-order* p q (1+ start) end))))
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