{"action":"created","issue":{"url":"https://api.github.com/repos/usnistgov/SP800-90B_EntropyAssessment/issues/18","repository_url":"https://api.github.com/repos/usnistgov/SP800-90B_EntropyAssessment","labels_url":"https://api.github.com/repos/usnistgov/SP800-90B_EntropyAssessment/issues/18/labels{/name}","comments_url":"https://api.github.com/repos/usnistgov/SP800-90B_EntropyAssessment/issues/18/comments","events_url":"https://api.github.com/repos/usnistgov/SP800-90B_EntropyAssessment/issues/18/events","html_url":"https://github.com/usnistgov/SP800-90B_EntropyAssessment/issues/18","id":186174758,"node_id":"MDU6SXNzdWUxODYxNzQ3NTg=","number":18,"title":"Evaluation of the function \"F\" should terminate sooner.","user":{"login":"joshuaehill","id":990213,"node_id":"MDQ6VXNlcjk5MDIxMw==","avatar_url":"https://avatars2.githubusercontent.com/u/990213?v=4","gravatar_id":"","url":"https://api.github.com/users/joshuaehill","html_url":"https://github.com/joshuaehill","followers_url":"https://api.github.com/users/joshuaehill/followers","following_url":"https://api.github.com/users/joshuaehill/following{/other_user}","gists_url":"https://api.github.com/users/joshuaehill/gists{/gist_id}","starred_url":"https://api.github.com/users/joshuaehill/starred{/owner}{/repo}","subscriptions_url":"https://api.github.com/users/joshuaehill/subscriptions","organizations_url":"https://api.github.com/users/joshuaehill/orgs","repos_url":"https://api.github.com/users/joshuaehill/repos","events_url":"https://api.github.com/users/joshuaehill/events{/privacy}","received_events_url":"https://api.github.com/users/joshuaehill/received_events","type":"User","site_admin":false},"labels":[],"state":"open","locked":false,"assignee":null,"assignees":[],"milestone":null,"comments":2,"created_at":"2016-10-30T23:52:04Z","updated_at":"2018-09-05T23:36:59Z","closed_at":null,"author_association":"NONE","body":"In the collision estimate, the function F is a continued fraction form of a portion of a incomplete Gamma function. When to stop evaluation of such a function requires some nuance, as the standard \"small distance from the prior iteration\" approach for series isn't reliable. Instead, this should use Steed's method (see http://dlmf.nist.gov/3.10#Px8) or some variation of Lentz's method (see his paper or Numerical Recipes).\r\n\r\nThe existing code seems to do something opaquely clever or just unreasonable: it does as many iterations as the number of symbols (k). It's not clear why this value is a reasonable value. My code seems to require fewer than about 4 dozen iterations normally, but this will depend on the value of the parameter being passed in. Doing extra work isn't without problem: error accumulates and ultimately makes the quality worse.\r\n\r\n*Edit: corrected observed number of rounds; caught by k to n rename. Sorry for the drifting comments.*\r\n"},"comment":{"url":"https://api.github.com/repos/usnistgov/SP800-90B_EntropyAssessment/issues/comments/418915183","html_url":"https://github.com/usnistgov/SP800-90B_EntropyAssessment/issues/18#issuecomment-418915183","issue_url":"https://api.github.com/repos/usnistgov/SP800-90B_EntropyAssessment/issues/18","id":418915183,"node_id":"MDEyOklzc3VlQ29tbWVudDQxODkxNTE4Mw==","user":{"login":"joshuaehill","id":990213,"node_id":"MDQ6VXNlcjk5MDIxMw==","avatar_url":"https://avatars2.githubusercontent.com/u/990213?v=4","gravatar_id":"","url":"https://api.github.com/users/joshuaehill","html_url":"https://github.com/joshuaehill","followers_url":"https://api.github.com/users/joshuaehill/followers","following_url":"https://api.github.com/users/joshuaehill/following{/other_user}","gists_url":"https://api.github.com/users/joshuaehill/gists{/gist_id}","starred_url":"https://api.github.com/users/joshuaehill/starred{/owner}{/repo}","subscriptions_url":"https://api.github.com/users/joshuaehill/subscriptions","organizations_url":"https://api.github.com/users/joshuaehill/orgs","repos_url":"https://api.github.com/users/joshuaehill/repos","events_url":"https://api.github.com/users/joshuaehill/events{/privacy}","received_events_url":"https://api.github.com/users/joshuaehill/received_events","type":"User","site_admin":false},"created_at":"2018-09-05T23:36:59Z","updated_at":"2018-09-05T23:36:59Z","author_association":"NONE","body":"As an aside, with the final SP800-90B, we are limited to the k=2 case. In this instance, F is just a polynomial; the function is F(z) = 2 z^3 + 2 z^2 + z. See my comment in Appendix G.1.1 of our implementation notes: http://bit.ly/2jwKN9R"}}
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