spielwiese
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Last change
on this file since cd86ac was
a43bd1,
checked in by Olaf Bachmann <obachman@…>, 24 years ago
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2000-08-04 Olaf Bachmann <obachman@mathematik.uni-kl.de>
* ffops.cc: initialize ff_prime to 0, so that first call
to
ff_setprime always initializes ff_invtab.
git-svn-id: file:///usr/local/Singular/svn/trunk@4507 2c84dea3-7e68-4137-9b89-c4e89433aadc
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-
Property mode set to
100644
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File size:
2.1 KB
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| 1 | /* emacs edit mode for this file is -*- C++ -*- */ |
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| 2 | /* $Id: ffops.cc,v 1.9 2000-08-04 11:10:15 obachman Exp $ */ |
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| 3 | |
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| 4 | #include <config.h> |
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| 5 | |
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| 6 | #include <string.h> |
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| 7 | |
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| 8 | #include "assert.h" |
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| 9 | |
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| 10 | #include "cf_defs.h" |
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| 11 | #include "ffops.h" |
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| 12 | |
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| 13 | int ff_prime = 0; |
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| 14 | int ff_halfprime = 0; |
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| 15 | bool ff_big = false; |
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| 16 | short * ff_invtab = new short [32767]; |
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| 17 | |
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| 18 | #ifdef __MWERKS__ |
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| 19 | #include <stuff_64.h> |
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| 20 | int ff_mul( const int a, const int b ) |
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| 21 | { |
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| 22 | Int_64 c; |
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| 23 | unsigned int ua, ub; |
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| 24 | int res; |
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| 25 | |
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| 26 | if ((!a) || (!b)) return 0; |
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| 27 | if (a>0) |
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| 28 | ua = a; |
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| 29 | else |
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| 30 | ua = -a; |
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| 31 | if (b>0) |
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| 32 | ub = b; |
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| 33 | else |
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| 34 | ub = -b; |
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| 35 | mul_64(&c, ua, ub); |
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| 36 | res = rem_64(&c, ff_prime); |
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| 37 | if ((a>0) != (b>0)) |
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| 38 | res = ff_prime-res; |
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| 39 | return res; |
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| 40 | } |
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| 41 | #endif |
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| 42 | |
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| 43 | void ff_setprime ( const int p ) |
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| 44 | { |
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| 45 | if ( p != ff_prime ) { |
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| 46 | ff_prime = p; |
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| 47 | ff_halfprime = ff_prime / 2; |
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| 48 | if ( ! ff_big ) |
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| 49 | memset( ff_invtab, 0, ff_prime*sizeof(short) ); |
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| 50 | } |
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| 51 | } |
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| 52 | |
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| 53 | int ff_newinv ( const int a ) |
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| 54 | { |
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| 55 | int p, q, r1, r2, y1, y2; |
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| 56 | if (a < 2) |
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| 57 | return (ff_invtab[a] = a); |
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| 58 | r1 = p = ff_prime; |
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| 59 | q = r1 / a; |
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| 60 | y1 = -q; |
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| 61 | r1 -= a * q; |
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| 62 | if (r1 == 1) |
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| 63 | { |
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| 64 | y1 += p; |
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| 65 | ff_invtab[y1] = a; |
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| 66 | return (ff_invtab[a] = y1); |
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| 67 | } |
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| 68 | r2 = a; |
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| 69 | y2 = 1; |
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| 70 | for (;;) |
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| 71 | { |
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| 72 | q = r2 / r1; |
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| 73 | y2 -= y1 * q; |
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| 74 | r2 -= r1 * q; |
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| 75 | if (r2 == 1) |
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| 76 | { |
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| 77 | if (y2 < 0) |
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| 78 | y2 += p; |
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| 79 | ff_invtab[y2] = a; |
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| 80 | return (ff_invtab[a] = y2); |
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| 81 | } |
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| 82 | q = r1 / r2; |
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| 83 | y1 -= y2 * q; |
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| 84 | r1 -= r2 * q; |
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| 85 | if (r1 == 1) |
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| 86 | { |
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| 87 | if (y1 < 0) |
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| 88 | y1 += p; |
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| 89 | ff_invtab[y1] = a; |
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| 90 | return (ff_invtab[a] = y1); |
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| 91 | } |
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| 92 | } |
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| 93 | } |
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| 94 | |
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| 95 | int ff_biginv ( const int a ) |
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| 96 | { |
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| 97 | int p, q, r1, r2, y1, y2; |
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| 98 | if (a < 2) |
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| 99 | return a; |
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| 100 | r1 = p = ff_prime; |
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| 101 | q = r1 / a; |
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| 102 | y1 = -q; |
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| 103 | r1 -= a * q; |
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| 104 | if (r1 == 1) |
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| 105 | return p + y1; |
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| 106 | r2 = a; |
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| 107 | y2 = 1; |
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| 108 | for (;;) |
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| 109 | { |
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| 110 | q = r2 / r1; |
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| 111 | y2 -= y1 * q; |
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| 112 | r2 -= r1 * q; |
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| 113 | if (r2 == 1) |
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| 114 | { |
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| 115 | if (y2 > 0) |
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| 116 | return y2; |
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| 117 | else |
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| 118 | return p + y2; |
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| 119 | } |
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| 120 | q = r1 / r2; |
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| 121 | y1 -= y2 * q; |
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| 122 | r1 -= r2 * q; |
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| 123 | if (r1 == 1) |
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| 124 | { |
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| 125 | if (y1 > 0) |
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| 126 | return y1; |
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| 127 | else |
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| 128 | return p + y1; |
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| 129 | } |
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| 130 | } |
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| 131 | } |
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