{"action":"created","issue":{"url":"https://api.github.com/repos/gap-system/gap/issues/887","repository_url":"https://api.github.com/repos/gap-system/gap","labels_url":"https://api.github.com/repos/gap-system/gap/issues/887/labels{/name}","comments_url":"https://api.github.com/repos/gap-system/gap/issues/887/comments","events_url":"https://api.github.com/repos/gap-system/gap/issues/887/events","html_url":"https://github.com/gap-system/gap/issues/887","id":171853495,"number":887,"title":"Bug with new fp code in IsomorphismFpGroupByGeneratorsNC","user":{"login":"laurentbartholdi","id":2230352,"avatar_url":"https://avatars.githubusercontent.com/u/2230352?v=3","gravatar_id":"","url":"https://api.github.com/users/laurentbartholdi","html_url":"https://github.com/laurentbartholdi","followers_url":"https://api.github.com/users/laurentbartholdi/followers","following_url":"https://api.github.com/users/laurentbartholdi/following{/other_user}","gists_url":"https://api.github.com/users/laurentbartholdi/gists{/gist_id}","starred_url":"https://api.github.com/users/laurentbartholdi/starred{/owner}{/repo}","subscriptions_url":"https://api.github.com/users/laurentbartholdi/subscriptions","organizations_url":"https://api.github.com/users/laurentbartholdi/orgs","repos_url":"https://api.github.com/users/laurentbartholdi/repos","events_url":"https://api.github.com/users/laurentbartholdi/events{/privacy}","received_events_url":"https://api.github.com/users/laurentbartholdi/received_events","type":"User","site_admin":false},"labels":[{"url":"https://api.github.com/repos/gap-system/gap/labels/bug","name":"bug","color":"e11d21"},{"url":"https://api.github.com/repos/gap-system/gap/labels/wrong%20result","name":"wrong result","color":"e11d21"}],"state":"open","locked":false,"assignee":null,"assignees":[],"milestone":null,"comments":17,"created_at":"2016-08-18T09:10:07Z","updated_at":"2016-08-21T10:29:37Z","closed_at":null,"body":"Observed behaviour\r\n-----------------\r\n\r\n```\r\ngap> src := FreeGroup(6);;\r\ngap> AssignGeneratorVariables(src);;\r\ngap> src := src / [f5*f4*f6*f2*f1*f3];;\r\ngap> AssignGeneratorVariables(src);;\r\ngap> gens := [ f3, f1, f2^-1*f4^-1*f2*f4*f2, f5*f4*f6*f4^-1*f5^-1, f2^-1*f4^-1*f2^-1*f4*f2*f4*f2, f5 ];;\r\ngap> fp := IsomorphismFpGroupByGeneratorsNC(src,gens,\"F\");;\r\ngap> dst := Image(fp);;\r\ngap> MappedWord(RelatorsOfFpGroup(dst)[1],GeneratorsOfGroup(FreeGroupOfFpGroup(dst)),gens);\r\nf2^-1*f4^-1*f2^-1*f4*f2*f4*f2*f5*f4*f6*f4^-1*f1*f3*f2^-1*f4^-1\r\n```\r\n\r\nExpected behaviour\r\n----------------\r\n\r\nThe relator should evaluate back to a trivial element in src (namely, a conjugate of f5*f4*f6*f2*f1*f3). It seems that the new code miscalculates the relator of the image.\r\n\r\nCopy and paste GAP banner (to tell us about your setup)\r\n-----------------------\r\nLatest sources from github:\r\n```\r\n ┌───────┐   GAP v4.8.1-1789-gd876566 of 2016-08-02 22:42:15 (CEST)\r\n │  GAP  │   http://www.gap-system.org\r\n └───────┘   Architecture: x86_64-apple-darwin13.4.0-gcc-default64\r\n Libs used:  gmp\r\n Loading the library and packages ...\r\n```\r\n"},"comment":{"url":"https://api.github.com/repos/gap-system/gap/issues/comments/241249899","html_url":"https://github.com/gap-system/gap/issues/887#issuecomment-241249899","issue_url":"https://api.github.com/repos/gap-system/gap/issues/887","id":241249899,"user":{"login":"laurentbartholdi","id":2230352,"avatar_url":"https://avatars.githubusercontent.com/u/2230352?v=3","gravatar_id":"","url":"https://api.github.com/users/laurentbartholdi","html_url":"https://github.com/laurentbartholdi","followers_url":"https://api.github.com/users/laurentbartholdi/followers","following_url":"https://api.github.com/users/laurentbartholdi/following{/other_user}","gists_url":"https://api.github.com/users/laurentbartholdi/gists{/gist_id}","starred_url":"https://api.github.com/users/laurentbartholdi/starred{/owner}{/repo}","subscriptions_url":"https://api.github.com/users/laurentbartholdi/subscriptions","organizations_url":"https://api.github.com/users/laurentbartholdi/orgs","repos_url":"https://api.github.com/users/laurentbartholdi/repos","events_url":"https://api.github.com/users/laurentbartholdi/events{/privacy}","received_events_url":"https://api.github.com/users/laurentbartholdi/received_events","type":"User","site_admin":false},"created_at":"2016-08-21T10:29:37Z","updated_at":"2016-08-21T10:29:37Z","body":"Here's something that doesn't work anymore, but used to work with the previous code and FGA:\r\n```\r\nsrc := FreeGroup(\"f1\",\"f2\",\"f3\",\"g1\",\"g2\",\"g3\");;\r\nAssignGeneratorVariables(src);;\r\nsrc := src / [ f3*f2*f1*g3*g2*g1 ];\r\nAssignGeneratorVariables(src);;\r\nmap := GroupHomomorphismByImages(src,src,[ f1, f2, f3, g1, g2, g3 ], [ f1, f2^-1*f3^-1*f2*f3*f2, f2^-1*f3*f2, g1, g2, g3 ]);;\r\nInverse(map); # waits forever\r\n```"}}
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