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Macaulay2Doc :: fine control of a Groebner basis computation

fine control of a Groebner basis computation

Sometimes a Groebner basis computation doesn't finish quickly enough. If so then this section might be of use. THIS PAGE IS UNDER CONSTRUCTION.

Partially computed Groebner bases

Suppose that you have computed part of a Groebner basis. For example, you may have interrupted the computation using CTRL-C (typing 'c' while holding the CTRL key down, in emacs, you have to type CTRL-C twice), or you may have given options requesting only partial computation.
i1 : R = ZZ/32003[a..e];
i2 : I = ideal(random(3,R),random(3,R),random(3,R))

                  3        2           2        3         2                
o2 = ideal (12627a  + 7498a b + 4059a*b  + 1522b  - 10435a c + 11541a*b*c +
     ------------------------------------------------------------------------
           2            2           2        3         2                
     11658b c - 14933a*c  - 10286b*c  + 4972c  + 13523a d - 12706a*b*d -
     ------------------------------------------------------------------------
          2                                  2            2          2  
     3348b d + 10993a*c*d + 5852b*c*d - 3655c d + 12147a*d  + 1135b*d  +
     ------------------------------------------------------------------------
             2        3       2                     2               
     10079c*d  - 3322d  - 172a e - 8105a*b*e + 9913b e - 2369a*c*e -
     ------------------------------------------------------------------------
                       2                                              2   
     8859b*c*e + 15089c e + 12315a*d*e + 7118b*d*e - 710c*d*e + 10677d e +
     ------------------------------------------------------------------------
            2           2          2          2        3         3        2 
     2428a*e  - 15078b*e  - 6049c*e  - 7675d*e  - 2258e , - 5642a  + 4757a b
     ------------------------------------------------------------------------
              2        3        2                      2           2  
     - 8746a*b  + 3171b  + 2534a c - 4464a*b*c + 11422b c - 6317a*c  +
     ------------------------------------------------------------------------
             2         3        2                      2                
     10185b*c  + 14969c  - 9634a d - 10058a*b*d + 5891b d + 11492a*c*d +
     ------------------------------------------------------------------------
                       2            2          2          2        3  
     4954b*c*d - 14933c d - 10221a*d  + 7489b*d  + 4526c*d  + 1886d  +
     ------------------------------------------------------------------------
          2                     2                                    2   
     6538a e + 1060a*b*e + 1001b e - 14482a*c*e - 11385b*c*e + 14847c e +
     ------------------------------------------------------------------------
                                               2            2           2  
     1672a*d*e + 14373b*d*e - 2054c*d*e + 1257d e - 11434a*e  - 14846b*e  +
     ------------------------------------------------------------------------
             2          2       3          3        2           2        3  
     12362c*e  + 4644d*e  - 980e , - 15615a  - 6540a b + 5340a*b  - 1328b  -
     ------------------------------------------------------------------------
          2                     2           2           2       3         2 
     1669a c + 340a*b*c - 14729b c - 8053a*c  - 13270b*c  + 757c  + 15734a d
     ------------------------------------------------------------------------
                        2                                  2           2  
     + 5471a*b*d + 1451b d - 4740a*c*d + 15191b*c*d - 1406c d + 8351a*d  +
     ------------------------------------------------------------------------
            2          2        3       2                      2   
     5572b*d  - 8004c*d  + 2089d  - 641a e + 15597a*b*e + 7572b e -
     ------------------------------------------------------------------------
                                    2                                       
     13288a*c*e + 7920b*c*e + 13285c e - 9013a*d*e - 8836b*d*e - 4119c*d*e -
     ------------------------------------------------------------------------
          2           2          2          2           2        3
     5809d e - 2247a*e  - 4373b*e  - 9033c*e  + 15014d*e  - 3046e )

o2 : Ideal of R
i3 : gens gb(I,PairLimit=>7);

             1       7
o3 : Matrix R  <--- R
Get the Groebner basis object:
i4 : g = gb(I,StopBeforeComputation => true);
i5 : leadTerm gens g

o5 = | ab2 a2b a3 b3c b4 abc3 a2c3 |

             1       7
o5 : Matrix R  <--- R
We can make a Groebner basis snapshot by using StopBeforeComputation, or gbSnapshot:
i6 : gens gb(I,StopBeforeComputation => true)

o6 = | ab2-15141b3+2034a2c-14447abc-1453b2c+23ac2+9236bc2+13221c3+1075a2d-
     ------------------------------------------------------------------------
     14576abd-1525b2d-911acd+9280bcd+3330c2d-12552ad2-12577bd2+5933cd2+7625d3
     ------------------------------------------------------------------------
     -14215a2e+14176abe+6057b2e+6678ace-11702bce+8468c2e-9613ade-4678bde+
     ------------------------------------------------------------------------
     2409cde+10058d2e+13220ae2+7612be2+6986ce2-11200de2-13462e3
     ------------------------------------------------------------------------
     a2b-15922b3+12986a2c-14487abc+14227b2c-14573ac2-13478bc2-5257c3+11465a2d
     ------------------------------------------------------------------------
     +13714abd+2047b2d+6515acd+7940bcd+13913c2d+10606ad2+6558bd2+15581cd2-
     ------------------------------------------------------------------------
     8476d3-10175a2e+11220abe-9664b2e+7451ace+1351bce-6766c2e-8686ade+
     ------------------------------------------------------------------------
     13074bde-5023cde-4225d2e+851ae2+8882be2+1411ce2+15145de2-5392e3
     ------------------------------------------------------------------------
     a3-13114b3+9259a2c+3074abc+1727b2c-6638ac2-152bc2-3670c3+1371a2d-
     ------------------------------------------------------------------------
     11729abd+12654b2d-7805acd-4504bcd-1075c2d+14828ad2-7665bd2+12283cd2+
     ------------------------------------------------------------------------
     15827d3+585a2e+14984abe+5645b2e-5593ace-8411bce-2254c2e-6773ade-5296bde-
     ------------------------------------------------------------------------
     8576cde-11746d2e+2025ae2-6929be2-9035ce2-7596de2+4660e3
     ------------------------------------------------------------------------
     b3c+13183a2c2+8293abc2+10325b2c2+5942ac3+3092bc3-2278c4-5480b3d+9627a2cd
     ------------------------------------------------------------------------
     +3243abcd-8761b2cd+11444ac2d+10666bc2d+1298c3d-7925a2d2-6246abd2-
     ------------------------------------------------------------------------
     14317b2d2+14172acd2+15011bcd2-6418c2d2+898ad3-4042bd3+13477cd3-11935d4+
     ------------------------------------------------------------------------
     13490b3e+15028a2ce-11959abce-8922b2ce-12407ac2e-5652bc2e+8031c3e+
     ------------------------------------------------------------------------
     15433a2de-10906abde+15433b2de+14362acde-9341bcde-13330c2de+11396ad2e+
     ------------------------------------------------------------------------
     6073bd2e+7979cd2e+15468d3e+4004a2e2-5425abe2-4232b2e2-6951ace2+11705bce2
     ------------------------------------------------------------------------
     -8076c2e2+6143ade2-13694bde2-3931cde2-12568d2e2+6101ae3-14825be3-
     ------------------------------------------------------------------------
     14958ce3-15470de3+11780e4
     ------------------------------------------------------------------------
     b4-6726a2c2-4451abc2+1953b2c2+2568ac3+373bc3+11319c4-11936b3d+11211a2cd+
     ------------------------------------------------------------------------
     14808abcd-6914b2cd+15780ac2d-1329bc2d+729c3d+5897a2d2+11132abd2+
     ------------------------------------------------------------------------
     12962b2d2-11112acd2-5439bcd2-2134c2d2-411ad3+15747bd3-4081cd3-9288d4-
     ------------------------------------------------------------------------
     6069b3e-11359a2ce+3777abce+10593b2ce-4666ac2e-8925bc2e+3402c3e+12750a2de
     ------------------------------------------------------------------------
     -4624abde+8346b2de+12138acde-13059bcde-4742c2de-6830ad2e-9641bd2e-
     ------------------------------------------------------------------------
     15679cd2e-4181d3e+236a2e2-3032abe2+11860b2e2+283ace2-15967bce2+11441c2e2
     ------------------------------------------------------------------------
     +6022ade2+7891bde2+8853cde2-13558d2e2-12975ae3-11950be3+2637ce3+11278de3
     ------------------------------------------------------------------------
     +7824e4 abc3+15703b2c3-98ac4-8378bc4-6609c5-4161a2c2d+4982abc2d-
     ------------------------------------------------------------------------
     1390b2c2d-7801ac3d-12114bc3d-3048c4d+13527b3d2+11963a2cd2+3931abcd2+
     ------------------------------------------------------------------------
     9409b2cd2-13782ac2d2+15387bc2d2-3469c3d2+8158a2d3+4311abd3+12745b2d3-
     ------------------------------------------------------------------------
     2554acd3+1318bcd3+13095c2d3+7151ad4+12099bd4+6462cd4-5226d5-3941a2c2e+
     ------------------------------------------------------------------------
     10684abc2e-10589b2c2e+9155ac3e+8292bc3e+10917c4e-7180b3de+6506a2cde+
     ------------------------------------------------------------------------
     7000abcde+12783b2cde+12633ac2de-3978bc2de+377c3de+5541a2d2e+6357abd2e+
     ------------------------------------------------------------------------
     12783b2d2e-9329acd2e-8196bcd2e-13691c2d2e-11507ad3e-8075bd3e-4461cd3e+
     ------------------------------------------------------------------------
     13054d4e+3941b3e2+15998a2ce2-5045abce2+11527b2ce2+13973ac2e2-15384bc2e2-
     ------------------------------------------------------------------------
     12342c3e2+6394a2de2-9365abde2+6047b2de2+4313acde2+2025bcde2+10925c2de2+
     ------------------------------------------------------------------------
     15050ad2e2-13518bd2e2-10552cd2e2-7157d3e2-6874a2e3+4608abe3+11404b2e3-
     ------------------------------------------------------------------------
     9488ace3+12126bce3+7218c2e3+5026ade3+14205bde3-7794cde3-1836d2e3+2365ae4
     ------------------------------------------------------------------------
     +10769be4+3597ce4+12079de4-5189e5
     ------------------------------------------------------------------------
     a2c3+11518b2c3+11347ac4+815bc4-3058c5-5259a2c2d-2701abc2d-14635b2c2d+
     ------------------------------------------------------------------------
     10235ac3d-8563bc3d-14611c4d-9774b3d2-13927a2cd2-13401abcd2-11536b2cd2+
     ------------------------------------------------------------------------
     8287ac2d2+11108bc2d2-7835c3d2+11792a2d3-8298abd3-3160b2d3-8514acd3+
     ------------------------------------------------------------------------
     4459bcd3+1942c2d3-10329ad4+14173bd4-12390cd4+31d5+6901a2c2e-15023abc2e+
     ------------------------------------------------------------------------
     7916b2c2e-10919ac3e+11572bc3e-14352c4e+10004b3de-11319a2cde-7722abcde+
     ------------------------------------------------------------------------
     5174b2cde+6611ac2de-8922bc2de-8523c3de-12558a2d2e+1200abd2e-4877b2d2e+
     ------------------------------------------------------------------------
     4441acd2e-2022bcd2e+11768c2d2e-14082ad3e+3138bd3e+8686cd3e+8695d4e-
     ------------------------------------------------------------------------
     3548b3e2-4473a2ce2-57abce2-4254b2ce2-1403ac2e2-4227bc2e2-11134c3e2-
     ------------------------------------------------------------------------
     6763a2de2+13293abde2-5637b2de2-5558acde2-10333bcde2+14537c2de2-7480ad2e2
     ------------------------------------------------------------------------
     +14136bd2e2+11412cd2e2-636d3e2-12237a2e3+8116abe3+13051b2e3+2920ace3+
     ------------------------------------------------------------------------
     6015bce3+779c2e3-15459ade3-6963bde3+8423cde3-8744d2e3+10524ae4+5726be4+
     ------------------------------------------------------------------------
     13025ce4-12458de4-6421e5 |

             1       7
o6 : Matrix R  <--- R
i7 : leadTerm gbSnapshot(I)

o7 = | ab2 a2b a3 b3c b4 abc3 a2c3 |

             1       7
o7 : Matrix R  <--- R