# HG changeset patch
# User Leif Leonhardy <not.really@online.de>
# Date 1275403412 -7200
# Node ID d7686100bc95d57234760f3ce78ed8deb0c07c44
# Parent 21acdff220a43f77712cd51cbd047e2184ae2f51
#9108 Marks time-consuming examples/doctests in symmetric_ideal.py with "long time".
Actually only two examples/lines time out on older/slower machines, but many other lines
depend on their results.
diff -r 21acdff220a4 -r d7686100bc95 sage/rings/polynomial/symmetric_ideal.py
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113 | 113 | |
114 | 114 | The default ordering is lexicographic. We now compute a Groebner basis:: |
115 | 115 | |
116 | | sage: J=I.groebner_basis() |
117 | | sage: J |
| 116 | sage: J=I.groebner_basis() ; J # long time |
118 | 117 | [y_1^5 + y_1^3, y_2*y_1^2 - y_1^3, y_2^2 - y_1^2, x_1*y_1^2 - y_1^4, x_1*y_2 - y_1^3, x_1^2 + y_1^2, x_2*y_1 - y_1^3] |
119 | 118 | |
120 | 119 | Ideal membership in ``I`` can now be tested by commuting symmetric reduction modulo ``J``:: |
121 | 120 | |
122 | | sage: I.reduce(J) |
| 121 | sage: I.reduce(J) # depends on long time example above |
123 | 122 | Symmetric Ideal (0, 0) of Infinite polynomial ring in x, y over Rational Field |
124 | 123 | |
125 | 124 | Note that the Groebner basis is not point-wise invariant under permutation. However, any element |
126 | 125 | of ``J`` has symmetric reduction zero even after applying a permutation:: |
127 | 126 | |
128 | 127 | sage: P=Permutation([1, 4, 3, 2]) |
129 | | sage: J[2] |
| 128 | sage: J[2] # depends on long time example above |
130 | 129 | y_2^2 - y_1^2 |
131 | | sage: J[2]^P |
| 130 | sage: J[2]^P # depends on long time example above |
132 | 131 | y_4^2 - y_1^2 |
133 | | sage: J.__contains__(J[2]^P) |
| 132 | sage: J.__contains__(J[2]^P) # depends on long time example above |
134 | 133 | False |
135 | | sage: [[(p^P).reduce(J) for p in J] for P in Permutations(4)] |
| 134 | sage: [[(p^P).reduce(J) for p in J] for P in Permutations(4)] # long time |
136 | 135 | [[0, 0, 0, 0, 0, 0, 0], |
137 | 136 | [0, 0, 0, 0, 0, 0, 0], |
138 | 137 | [0, 0, 0, 0, 0, 0, 0], |
… |
… |
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161 | 160 | Since ``I`` is not a Groebner basis, it is no surprise that it can not detect |
162 | 161 | ideal membership:: |
163 | 162 | |
164 | | sage: [p.reduce(I) for p in J] |
| 163 | sage: [p.reduce(I) for p in J] # depends on long time example above |
165 | 164 | [y_1^5 + y_1^3, y_2*y_1^2 - y_1^3, y_2^2 - y_1^2, x_1*y_1^2 - y_1^4, x_1*y_2 - y_1^3, -y_2^2 + y_1^2, x_2*y_1 - y_1^3] |
166 | 165 | |
167 | 166 | Note that we give no guarantee that the computation of a symmetric Groebner basis will terminate in |