Log function and documentation revamp #18970

rwst · 2015-07-30T06:51:22Z

From https://groups.google.com/forum/?hl=en#!topic/sage-devel/hwm-7V8S3hE

sage: log(int(8),2)
log(8)/log(2)
sage: log(8,int(2))
log(8)/log(2)
sage: log(8,2)
3

Also:
sage: log(1/8,2)
log(1/8)/log(2)

sage: ((-1)^(-I*log(3)/pi)).n()
3.00000000000000
sage: log(3,-1)
...
ValueError: m must be positive

Depends on #21623
Depends on #21517
Depends on #21518

Component: symbolics

Author: Ralf Stephan

Branch/Commit: b0486c8

Reviewer: Travis Scrimshaw

Issue created by migration from https://trac.sagemath.org/ticket/18970

The text was updated successfully, but these errors were encountered:

rwst · 2015-07-30T07:41:18Z

Branch: u/rws/always_simplify_log_a_m_a__to_m_for_any_a_m_coercible_to_integer

rwst · 2015-07-30T07:42:03Z

Author: Ralf Stephan

rwst · 2015-07-30T07:42:03Z

New commits:

`0086ec0`	`18970: always simplify log(a^m,a) if possible`

rwst · 2015-07-30T07:42:03Z

Commit: 0086ec0

sagetrac-git · 2015-07-30T07:56:48Z

Branch pushed to git repo; I updated commit sha1. New commits:

`92d9762`	`18970: fix`

sagetrac-git · 2015-07-30T07:56:48Z

Changed commit from 0086ec0 to 92d9762

dkrenn · 2015-07-30T08:21:50Z

comment:6

Before this patch

sage: %timeit log(QQ(8),2)
The slowest run took 5.08 times longer than the fastest. This could mean that an intermediate result is being cached 
10000 loops, best of 3: 39.4 µs per loop
sage: %timeit log(QQ(8),3)
10000 loops, best of 3: 38.1 µs per loop
sage: %timeit log(ZZ(8),3)
10000 loops, best of 3: 32.8 µs per loop
sage: %timeit log(ZZ(8),2)
The slowest run took 14.52 times longer than the fastest. This could mean that an intermediate result is being cached 
1000000 loops, best of 3: 1.12 µs per loop

After

sage: %timeit log(QQ(8),3)
The slowest run took 37.28 times longer than the fastest. This could mean that an intermediate result is being cached 
10000 loops, best of 3: 48.8 µs per loop
sage: %timeit log(QQ(8),2)
The slowest run took 8.69 times longer than the fastest. This could mean that an intermediate result is being cached 
100000 loops, best of 3: 5.43 µs per loop
sage: %timeit log(ZZ(8),3)
10000 loops, best of 3: 48.4 µs per loop
sage: %timeit log(ZZ(8),2)
The slowest run took 8.80 times longer than the fastest. This could mean that an intermediate result is being cached 
100000 loops, best of 3: 5.34 µs per loop

I've repeated (differently) it due to the caching-warnings. Before

sage: timeit('log(QQ(8),3)', number=1, repeat=1)
1 loops, best of 1: 191 µs per loop
sage: timeit('log(QQ(8),2)', number=1, repeat=1)
1 loops, best of 1: 150 µs per loop
sage: timeit('log(ZZ(8),3)', number=1, repeat=1)
1 loops, best of 1: 125 µs per loop
sage: timeit('log(ZZ(8),2)', number=1, repeat=1)
1 loops, best of 1: 24.1 µs per loop

After

sage: timeit('log(QQ(8),3)', number=1, repeat=1)
1 loops, best of 1: 1.93 ms per loop
sage: timeit('log(QQ(8),2)', number=1, repeat=1)
1 loops, best of 1: 45.1 µs per loop
sage: timeit('log(ZZ(8),3)', number=1, repeat=1)
1 loops, best of 1: 158 µs per loop
sage: timeit('log(ZZ(8),2)', number=1, repeat=1)
1 loops, best of 1: 45.1 µs per loop

In particular log(QQ(8),3) becomes much slower (and only log(QQ(8),2) gains speed).

dkrenn · 2015-07-30T08:26:25Z

comment:7

sage: log(QQ(8),2).parent()
Integer Ring

which is a different behavior compared to the common/similar arithmetic operations (e.g. (QQ(2)^ZZ(1)).parent() is Rational Field and not Integer Ring) and I would expect that the logarithm of a rational is again a rational (if possible) or something where QQ coerces into (but not out of something which coerces into QQ).

rwst · 2015-07-30T08:56:21Z

comment:8

Is this a one-time comment, or do you plan to review to the end?

dkrenn · 2015-07-30T09:18:13Z

comment:9

Replying to @rwst:

Is this a one-time comment, or do you plan to review to the end?

Does this make a difference on how to react to my comment? ;) ....or more seriously: I am not sure if I feel qualified enough to review a change in the log-function. I just saw the discussion on sage-devel and looked into the ticket and decided to give some comments.

rwst · 2016-08-30T15:03:56Z

comment:11

The code at hand unconditionally tries to coerce the arguments into ZZ,QQ instead of checking the type first. Apart from the speed issue it also would benefit from moving completely into GiNaC: atm some cases are intercepted unnecessarily in Function_log.__call__ which itself awkwardly calls Pynac.

nexttime · 2016-08-30T15:28:29Z

comment:12

I guess some of the speed regression is due to the at least partially redundant checking whether arg == base**v, and of course now in addition computing the valuation first in case the latter does not hold. (At least it seemed to when I looked at it yesterday...)

Not sure how much the probably superfluous coercion contributes.

rwst · 2016-09-07T08:13:53Z

Changed branch from u/rws/always_simplify_log_a_m_a__to_m_for_any_a_m_coercible_to_integer to u/rws/18970-1

rwst · 2016-09-07T08:15:23Z

Dependencies: pynac-0.6.91

rwst · 2016-09-07T08:15:23Z

comment:14

New branch depends on Pynac git master.

New commits:

`11a81ee`	`18970: add two-arg log()`

rwst · 2016-09-07T08:15:23Z

Changed commit from 92d9762 to 11a81ee

rwst · 2016-09-07T08:32:27Z

comment:15

Timings with this branch. Before:

sage: %timeit log(QQ(8),2)
The slowest run took 10.96 times longer than the fastest. This could mean that an intermediate result is being cached.
10000 loops, best of 3: 40.1 µs per loop
sage: %timeit log(QQ(8),2)
10000 loops, best of 3: 40.2 µs per loop
sage: %timeit log(QQ(8),3)
10000 loops, best of 3: 40.5 µs per loop
sage: %timeit log(ZZ(8),3)
10000 loops, best of 3: 34.4 µs per loop
sage: %timeit log(ZZ(8),2)
The slowest run took 19.11 times longer than the fastest. This could mean that an intermediate result is being cached.
1000000 loops, best of 3: 886 ns per loop

After:

sage: %timeit log(QQ(8),2)
The slowest run took 15.53 times longer than the fastest. This could mean that an intermediate result is being cached.
10000 loops, best of 3: 26.7 µs per loop
sage: %timeit log(QQ(8),3)
The slowest run took 10.80 times longer than the fastest. This could mean that an intermediate result is being cached.
10000 loops, best of 3: 26.8 µs per loop
sage: %timeit log(ZZ(8),3)
10000 loops, best of 3: 30.2 µs per loop
sage: %timeit log(ZZ(8),2)
The slowest run took 17.37 times longer than the fastest. This could mean that an intermediate result is being cached.
1000000 loops, best of 3: 686 ns per loop

The single run measurements vary so much from run to run that I refrain from giving them here. The After values of timeit('log(QQ(8),3)', number=1, repeat=1) are however in the same range as the Before values (as well as the others).

fchapoton · 2017-10-20T20:08:01Z

comment:29

does not apply

sagetrac-git · 2017-10-21T05:57:30Z

Changed commit from 3c34001 to e46bc47

sagetrac-git · 2017-10-21T05:57:30Z

Branch pushed to git repo; I updated commit sha1. New commits:

`94cc4a5`	`Merge branch 'develop' into t/18970/18970-2`
`e46bc47`	`18970: fix and robustify doctests`

tscrim · 2017-10-23T23:26:55Z

comment:32

Needs another rebase over beta9.

sagetrac-git · 2017-10-24T06:21:41Z

Changed commit from e46bc47 to 7ab331e

sagetrac-git · 2017-10-24T06:21:41Z

Branch pushed to git repo; I updated commit sha1. New commits:

`7ab331e`	`Merge branch 'develop' into t/18970/18970-2`

sagetrac-git · 2017-10-24T15:29:07Z

Changed commit from 7ab331e to b3b9a52

sagetrac-git · 2017-10-24T15:29:07Z

Branch pushed to git repo; I updated commit sha1. New commits:

`b3b9a52`	`18970: fix log usage`

rwst · 2017-10-24T15:34:51Z

Changed branch from u/rws/18970-2 to u/rws/18970-3

rwst · 2017-10-24T15:35:45Z

Changed commit from b3b9a52 to b0486c8

rwst · 2017-10-24T15:35:45Z

comment:37

Fixes were added, cruft removed, and it all squashed.

New commits:

`b0486c8`	`18970: Log function and documentation revamp`

tscrim · 2017-10-25T14:58:45Z

Reviewer: Travis Scrimshaw

tscrim · 2017-10-25T14:58:45Z

comment:38

LGTM. Timings on my laptop with branch:

sage: %timeit log(QQ(8),2)
The slowest run took 29.31 times longer than the fastest. This could mean that an intermediate result is being cached.
1000000 loops, best of 3: 1.57 µs per loop
sage: %timeit log(QQ(8),3)
The slowest run took 4.03 times longer than the fastest. This could mean that an intermediate result is being cached.
10000 loops, best of 3: 35.5 µs per loop
sage: %timeit log(ZZ(8),3)
10000 loops, best of 3: 33 µs per loop
sage: %timeit log(ZZ(8),2)
The slowest run took 16.93 times longer than the fastest. This could mean that an intermediate result is being cached.
1000000 loops, best of 3: 887 ns per loop

vs. with develop:

sage: %timeit log(QQ(8),2)
The slowest run took 14987.26 times longer than the fastest. This could mean that an intermediate result is being cached.
1000000 loops, best of 3: 1.6 µs per loop
sage: %timeit log(QQ(8),3)
10000 loops, best of 3: 43.2 µs per loop
sage: %timeit log(ZZ(8),3)
The slowest run took 4.42 times longer than the fastest. This could mean that an intermediate result is being cached.
10000 loops, best of 3: 38.9 µs per loop
sage: %timeit log(ZZ(8),2)
The slowest run took 14.23 times longer than the fastest. This could mean that an intermediate result is being cached.
1000000 loops, best of 3: 1.06 µs per loop

rwst · 2017-10-26T06:25:14Z

comment:39

Thanks.

vbraun · 2017-10-29T10:32:17Z

Changed branch from u/rws/18970-3 to b0486c8

rwst added this to the sage-6.9 milestone Jul 30, 2015

rwst added c: symbolics labels Jul 30, 2015

rwst changed the title ~~always simplify log(a^m,a) to m for any m coercible to Integer~~ always simplify log(a^m,a) to m for any a,m coercible to Integer Jul 30, 2015

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nexttime mannequin modified the milestones: sage-6.9, sage-7.4 Aug 29, 2016

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rwst added this to the sage-8.1 milestone Aug 24, 2017

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vbraun closed this as completed in d6f7f9e Oct 29, 2017

rwst mentioned this issue Oct 21, 2016

Upgrade to pynac-0.6.91 #21623

Closed

fchapoton mentioned this issue Dec 11, 2017

Doctest fix for: wrong symbolic comparison of log #23224

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Log function and documentation revamp #18970

Log function and documentation revamp #18970

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Log function and documentation revamp #18970

Log function and documentation revamp #18970

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