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cf_util.cc
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1/* emacs edit mode for this file is -*- C++ -*- */
2
3/**
4 *
5 * @file cf_util.cc
6 *
7 * miscellaneous functions, not necessarily related
8 * to canonical forms.
9 *
10 * Used by: fac_cantzass.cc, gfops.cc
11 *
12**/
13
14
15#include "globaldefs.h"
16#include "config.h"
17#include "cf_util.h"
18
19
20/** int ipower ( int b, int m )
21 *
22 * ipower() - calculate b^m in standard integer arithmetic.
23 *
24 * Note: Beware of overflows.
25 *
26**/
27int ipower ( int b, int m )
28{
29 int prod = 1;
30
31 while ( m != 0 )
32 {
33 if ( m % 2 != 0 )
34 prod *= b;
35 m /= 2;
36 if ( m != 0 )
37 b *= b;
38 }
39 return prod;
40}
41
42int ilog2 (int v)
43{
44 const unsigned int b[] = {0x2, 0xC, 0xF0, 0xFF00, 0xFFFF0000};
45 const unsigned int S[] = {1, 2, 4, 8, 16};
46
47 unsigned int r = 0; // result of log2(v) will go here
48 if (v & b[4]) { v >>= S[4]; r |= S[4]; }
49 if (v & b[3]) { v >>= S[3]; r |= S[3]; }
50 if (v & b[2]) { v >>= S[2]; r |= S[2]; }
51 if (v & b[1]) { v >>= S[1]; r |= S[1]; }
52 if (v & b[0]) { v >>= S[0]; r |= S[0]; }
53 return (int)r;
54}
55
56int igcd( int a, int b )
57{
58 if ( a < 0 ) a = -a;
59 if ( b < 0 ) b = -b;
60
61 int c;
62
63 while ( b != 0 )
64 {
65 c = a % b;
66 a = b;
67 b = c;
68 }
69 return a;
70}
71
72#include<stdio.h>
73#include<stdlib.h>
74
75void factoryError_intern(const char *s)
76{
77 fputs(s,stderr);
78 abort();
79}
80VAR void (*factoryError)(const char *s) = factoryError_intern;
81
82
int m
Definition: cfEzgcd.cc:128
CanonicalForm b
Definition: cfModGcd.cc:4103
VAR void(* factoryError)(const char *s)
Definition: cf_util.cc:80
int ilog2(int v)
Definition: cf_util.cc:42
int igcd(int a, int b)
Definition: cf_util.cc:56
void factoryError_intern(const char *s)
Definition: cf_util.cc:75
int ipower(int b, int m)
int ipower ( int b, int m )
Definition: cf_util.cc:27
const CanonicalForm int s
Definition: facAbsFact.cc:51
const Variable & v
< [in] a sqrfree bivariate poly
Definition: facBivar.h:39
fq_nmod_poly_t prod
Definition: facHensel.cc:100
#define VAR
Definition: globaldefs.h:5