1 | /**************************************** |
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2 | * Computer Algebra System SINGULAR * |
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3 | ****************************************/ |
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4 | /* $Id$ */ |
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5 | |
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6 | /*************************************************************** |
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7 | * |
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8 | * File: polys-impl.cc |
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9 | * Purpose: low-level procuders for polys. |
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10 | * |
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11 | * If you touch anything here, you better know what you are doing. |
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12 | * What is here should not be used directly from other routines -- the |
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13 | * encapsulations in polys.[h,cc] should be used, instead. |
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14 | * |
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15 | ***************************************************************/ |
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16 | #ifndef POLYS_IMPL_CC |
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17 | #define POLYS_IMPL_CC |
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18 | |
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19 | #include <stdio.h> |
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20 | #include <string.h> |
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21 | |
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22 | #include "config.h" |
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23 | |
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24 | #include <omalloc/omalloc.h> |
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25 | #include <misc/auxiliary.h> |
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26 | |
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27 | #ifdef PDEBUG |
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28 | #undef NO_INLINE3 |
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29 | #define NO_INLINE3 |
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30 | #endif |
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31 | #include <polys/monomials/polys-impl.h> |
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32 | |
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33 | #include <polys/monomials/ring.h> |
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34 | #include <reporter/reporter.h> |
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35 | #include <coeffs/numbers.h> |
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36 | #include <polys/monomials/ring.h> |
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37 | #include <polys/monomials/p_polys.h> |
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38 | #include <reporter/reporter.h> |
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39 | |
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40 | #ifdef PDEBUG |
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41 | int pDBsyzComp=0; |
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42 | #endif |
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43 | |
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44 | /*************************************************************** |
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45 | * |
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46 | * Storage Managament Routines |
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47 | * |
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48 | ***************************************************************/ |
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49 | |
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50 | |
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51 | static inline unsigned long GetBitFields(long e, |
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52 | unsigned int s, unsigned int n) |
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53 | { |
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54 | #define Sy_bit_L(x) (((unsigned long)1L)<<(x)) |
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55 | unsigned int i = 0; |
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56 | unsigned long ev = 0L; |
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57 | assume(n > 0 && s < BIT_SIZEOF_LONG); |
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58 | do |
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59 | { |
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60 | assume(s+i < BIT_SIZEOF_LONG); |
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61 | if (e > (long) i) ev |= Sy_bit_L(s+i); |
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62 | else break; |
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63 | i++; |
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64 | } |
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65 | while (i < n); |
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66 | return ev; |
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67 | } |
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68 | |
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69 | // Short Exponent Vectors are used for fast divisibility tests |
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70 | // ShortExpVectors "squeeze" an exponent vector into one word as follows: |
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71 | // Let n = BIT_SIZEOF_LONG / pVariables. |
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72 | // If n == 0 (i.e. pVariables > BIT_SIZE_OF_LONG), let m == the number |
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73 | // of non-zero exponents. If (m>BIT_SIZEOF_LONG), then sev = ~0, else |
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74 | // first m bits of sev are set to 1. |
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75 | // Otherwise (i.e. pVariables <= BIT_SIZE_OF_LONG) |
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76 | // represented by a bit-field of length n (resp. n+1 for some |
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77 | // exponents). If the value of an exponent is greater or equal to n, then |
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78 | // all of its respective n bits are set to 1. If the value of an exponent |
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79 | // is smaller than n, say m, then only the first m bits of the respective |
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80 | // n bits are set to 1, the others are set to 0. |
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81 | // This way, we have: |
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82 | // exp1 / exp2 ==> (ev1 & ~ev2) == 0, i.e., |
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83 | // if (ev1 & ~ev2) then exp1 does not divide exp2 |
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84 | unsigned long p_GetShortExpVector(poly p, const ring r) |
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85 | { |
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86 | assume(p != NULL); |
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87 | if (p == NULL) return 0; |
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88 | unsigned long ev = 0; // short exponent vector |
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89 | unsigned int n = BIT_SIZEOF_LONG / r->N; // number of bits per exp |
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90 | unsigned int m1; // highest bit which is filled with (n+1) |
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91 | unsigned int i = 0, j=1; |
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92 | |
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93 | if (n == 0) |
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94 | { |
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95 | if (r->N <2*BIT_SIZEOF_LONG) |
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96 | { |
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97 | n=1; |
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98 | m1=0; |
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99 | } |
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100 | else |
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101 | { |
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102 | for (; j<=(unsigned long) r->N; j++) |
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103 | { |
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104 | if (p_GetExp(p,j,r) > 0) i++; |
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105 | if (i == BIT_SIZEOF_LONG) break; |
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106 | } |
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107 | if (i>0) |
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108 | ev = ~((unsigned long)0) >> ((unsigned long) (BIT_SIZEOF_LONG - i)); |
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109 | return ev; |
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110 | } |
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111 | } |
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112 | else |
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113 | { |
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114 | m1 = (n+1)*(BIT_SIZEOF_LONG - n*r->N); |
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115 | } |
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116 | |
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117 | n++; |
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118 | while (i<m1) |
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119 | { |
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120 | ev |= GetBitFields(p_GetExp(p, j,r), i, n); |
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121 | i += n; |
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122 | j++; |
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123 | } |
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124 | |
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125 | n--; |
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126 | while (i<BIT_SIZEOF_LONG) |
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127 | { |
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128 | ev |= GetBitFields(p_GetExp(p, j,r), i, n); |
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129 | i += n; |
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130 | j++; |
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131 | } |
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132 | return ev; |
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133 | } |
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134 | |
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135 | #endif // POLYS_IMPL_CC |
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