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[Merged by Bors] - feat(analysis/convex/specific_functions): log is concave #5508

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@dupuisf dupuisf commented Dec 27, 2020

This PR proves that the real log is concave on Ioi 0 and Iio 0, and adds lemmas about concavity of functions along the way.


@dupuisf dupuisf added the awaiting-review The author would like community review of the PR label Dec 27, 2020
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Thanks for this!

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dupuisf and others added 2 commits December 27, 2020 18:30
Co-authored-by: hrmacbeth <25316162+hrmacbeth@users.noreply.github.com>
Co-authored-by: hrmacbeth <25316162+hrmacbeth@users.noreply.github.com>
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more of the same :)

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dupuisf and others added 8 commits December 28, 2020 10:11
Co-authored-by: hrmacbeth <25316162+hrmacbeth@users.noreply.github.com>
Co-authored-by: hrmacbeth <25316162+hrmacbeth@users.noreply.github.com>
Co-authored-by: hrmacbeth <25316162+hrmacbeth@users.noreply.github.com>
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bors bot commented Dec 29, 2020

✌️ dupuisf can now approve this pull request. To approve and merge a pull request, simply reply with bors r+. More detailed instructions are available here.

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Couple more things, also could you mention concave_on_log_Ioi and friend in the module docstring of convex.specific_functions?

Apart from this, looks good!

bors d+

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Comment on lines +131 to +135
{ intros x hx,
rw [function.iterate_succ, function.iterate_one],
change (deriv (deriv log)) x ≤ 0,
rw [deriv_log', deriv_inv (show x ≠ 0, by {rintro rfl, exact lt_irrefl 0 hx})],
exact neg_nonpos.mpr (inv_nonneg.mpr (pow_two_nonneg x)) }
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I just wrote a quick PR #5521, which will let this be simplified to

  { intros x hx,
    simp [function.iterate_succ, function.iterate_one, pow_two_nonneg] }

Let's not hold your PR up for this though.

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Nice!

@hrmacbeth hrmacbeth added delegated The PR author may merge after reviewing final suggestions. and removed awaiting-review The author would like community review of the PR labels Dec 29, 2020
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dupuisf commented Dec 29, 2020

bors r+

bors bot pushed a commit that referenced this pull request Dec 29, 2020
This PR proves that the real log is concave on `Ioi 0` and `Iio 0`, and adds lemmas about concavity of functions along the way.




Co-authored-by: Frédéric Dupuis <31101893+dupuisf@users.noreply.github.com>
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bors bot commented Dec 29, 2020

Pull request successfully merged into master.

Build succeeded:

@bors bors bot changed the title feat(analysis/convex/specific_functions): log is concave [Merged by Bors] - feat(analysis/convex/specific_functions): log is concave Dec 29, 2020
@bors bors bot closed this Dec 29, 2020
@bors bors bot deleted the dupuisf_log_is_concave branch December 29, 2020 20:36
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