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Merged
merged 1 commit into from
Oct 11, 2023
Merged

quick exit for expand_log(log(a*b**e)/log(b)) #25751

merged 1 commit into from
Oct 11, 2023

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smichr
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@smichr smichr commented Oct 1, 2023 •
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References to other Issues or PRs

Brief description of what is fixed or changed

master:

>>> expand_log(log(2*10)/log(10))
log(20)/log(10)
>>> _.expand(log=True)
log(20)/log(10)
>>> expand(_, factor=True)
2*log(2)/(log(2) + log(5)) + log(5)/(log(2) + log(5))

now

>>> (log(2*10)/log(10)).expand(log=True)
log(20)/log(10)
>>> expand_log(log(2*10)/log(10))
1 + log(2)/log(10)

Other comments

While factoring a single logs argument might be avoided because of the size of a number, when there is a ratio of logs, the lower arg gives a hint of what to check for in the upper. This would be easier to detect if log(a,b) did not auto evaluate to log(a)/log(b).

I don't really like that expand(..., log=True) does nothing. Maybe the action of this PR should be done if factor is false but log is true.

I would prefer to have log(x, i) remain unevaluated instead of rewriting to log(x)/log(i).

Release Notes

  • core
    • expand_log now detects the ratio log(a)/log(b) and will simplify if a == c*b**m

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sympy-bot commented Oct 1, 2023 •
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✅

Hi, I am the SymPy bot. I'm here to help you write a release notes entry. Please read the guide on how to write release notes.

Your release notes are in good order.

Here is what the release notes will look like:

  • core
    • expand_log now detects the ratio log(a)/log(b) and will simplify if a == c*b**m (#25751 by @smichr)

This will be added to https://github.com/sympy/sympy/wiki/Release-Notes-for-1.13.

Click here to see the pull request description that was parsed. 
<!-- Your title above should be a short description of what
was changed. Do not include the issue number in the title. -->

#### References to other Issues or PRs
<!-- If this pull request fixes an issue, write "Fixes #NNNN" in that exact
format, e.g. "Fixes #1234" (see
https://tinyurl.com/auto-closing for more information). Also, please
write a comment on that issue linking back to this pull request once it is
open. -->


#### Brief description of what is fixed or changed

master:
```python
>>> expand_log(log(2*10)/log(10))
log(20)/log(10)
>>> _.expand(log=True)
log(20)/log(10)
>>> expand(_, factor=True)
2*log(2)/(log(2) + log(5)) + log(5)/(log(2) + log(5))
```
now
```python
>>> (log(2*10)/log(10)).expand(log=True)
log(20)/log(10)
>>> expand_log(log(2*10)/log(10))
1 + log(2)/log(10)
```
#### Other comments
While factoring a single logs argument might be avoided because of the size of a number, when there is a ratio of logs, the lower arg gives a hint of what to check for in the upper. This would be easier to detect if log(a,b) did not auto evaluate to log(a)/log(b).

I don't really like that `expand(..., log=True)` does nothing. Maybe the action of this PR should be done if factor is false but log is true.

I would prefer to have `log(x, i)` remain unevaluated instead of rewriting to `log(x)/log(i)`.

#### Release Notes

<!-- Write the release notes for this release below between the BEGIN and END
statements. The basic format is a bulleted list with the name of the subpackage
and the release note for this PR. For example:

* solvers
  * Added a new solver for logarithmic equations.

* functions
  * Fixed a bug with log of integers. Formerly, `log(-x)` incorrectly gave `-log(x)`.

* physics.units
  * Corrected a semantical error in the conversion between volt and statvolt which
    reported the volt as being larger than the statvolt.

or if no release note(s) should be included use:

NO ENTRY

See https://github.com/sympy/sympy/wiki/Writing-Release-Notes for more
information on how to write release notes. The bot will check your release
notes automatically to see if they are formatted correctly. -->

<!-- BEGIN RELEASE NOTES -->
* core
  * `expand_log` now detects the ratio `log(a)/log(b)` and will simplify if `a == c*b**m`
<!-- END RELEASE NOTES -->

Update

The release notes on the wiki have been updated.

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github-actions bot commented Oct 1, 2023 •
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Benchmark results from GitHub Actions

Lower numbers are good, higher numbers are bad. A ratio less than 1
means a speed up and greater than 1 means a slowdown. Green lines
beginning with + are slowdowns (the PR is slower then master or
master is slower than the previous release). Red lines beginning
with - are speedups.

Significantly changed benchmark results (PR vs master)



Significantly changed benchmark results (master vs previous release)


| Change   | Before [8059df73] <sympy-1.12^0>   | After [6e347f05]    |   Ratio | Benchmark (Parameter)                                                |
|----------|------------------------------------|---------------------|---------|----------------------------------------------------------------------|
| -        | 83.5±0.5ms                         | 55.1±0.3ms          |    0.66 | integrate.TimeIntegrationRisch02.time_doit(10)                       |
| -        | 82.0±0.2ms                         | 54.5±0.3ms          |    0.66 | integrate.TimeIntegrationRisch02.time_doit_risch(10)                 |
| +        | 20.0±0.2μs                         | 40.1±0.2μs          |    2    | integrate.TimeIntegrationRisch03.time_doit(1)                        |
| -        | 6.89±0.02ms                        | 3.67±0.01ms         |    0.53 | logic.LogicSuite.time_load_file                                      |
| -        | 2.11±0ms                           | 624±6μs             |    0.3  | polys.TimePREM_LinearDenseQuadraticGCD.time_op(3, 'sparse')          |
| -        | 10.4±0.03ms                        | 1.88±0ms            |    0.18 | polys.TimePREM_LinearDenseQuadraticGCD.time_op(5, 'sparse')          |
| -        | 368±2μs                            | 79.3±0.1μs          |    0.22 | polys.TimePREM_QuadraticNonMonicGCD.time_op(1, 'sparse')             |
| -        | 4.73±0.01ms                        | 349±2μs             |    0.07 | polys.TimePREM_QuadraticNonMonicGCD.time_op(3, 'sparse')             |
| -        | 10.6±0.03ms                        | 1.05±0.01ms         |    0.1  | polys.TimePREM_QuadraticNonMonicGCD.time_op(5, 'sparse')             |
| -        | 6.30±0.02ms                        | 3.81±0.01ms         |    0.6  | polys.TimeSUBRESULTANTS_LinearDenseQuadraticGCD.time_op(2, 'sparse') |
| -        | 27.7±0.06ms                        | 11.6±0.01ms         |    0.42 | polys.TimeSUBRESULTANTS_LinearDenseQuadraticGCD.time_op(3, 'sparse') |
| -        | 6.81±0.05ms                        | 1.12±0ms            |    0.17 | polys.TimeSUBRESULTANTS_QuadraticNonMonicGCD.time_op(1, 'sparse')    |
| -        | 16.0±0.09ms                        | 9.01±0.05ms         |    0.56 | polys.TimeSUBRESULTANTS_QuadraticNonMonicGCD.time_op(2, 'sparse')    |
| -        | 206±0.2ms                          | 68.6±0.09ms         |    0.33 | polys.TimeSUBRESULTANTS_QuadraticNonMonicGCD.time_op(3, 'sparse')    |
| -        | 6.37±0.01ms                        | 508±0.7μs           |    0.08 | polys.TimeSUBRESULTANTS_SparseGCDHighDegree.time_op(3, 'sparse')     |
| -        | 27.3±0.05ms                        | 809±2μs             |    0.03 | polys.TimeSUBRESULTANTS_SparseGCDHighDegree.time_op(5, 'sparse')     |
| -        | 594±1μs                            | 201±0.3μs           |    0.34 | polys.TimeSUBRESULTANTS_SparseNonMonicQuadratic.time_op(1, 'sparse') |
| -        | 6.34±0.02ms                        | 205±0.5μs           |    0.03 | polys.TimeSUBRESULTANTS_SparseNonMonicQuadratic.time_op(3, 'sparse') |
| -        | 16.5±0.04ms                        | 208±1μs             |    0.01 | polys.TimeSUBRESULTANTS_SparseNonMonicQuadratic.time_op(5, 'sparse') |
| -        | 162±0.5μs                          | 90.9±0.3μs          |    0.56 | solve.TimeMatrixOperations.time_rref(3, 0)                           |
| -        | 304±0.5μs                          | 108±0.5μs           |    0.35 | solve.TimeMatrixOperations.time_rref(4, 0)                           |
| -        | 30.0±0.08ms                        | 12.7±0.02ms         |    0.42 | solve.TimeSolveLinSys189x49.time_solve_lin_sys                       |



Full benchmark results can be found as artifacts in GitHub Actions

(click on checks at the top of the PR).

      		
    

  





        


            

            
            

              
            

        

      


      

            
  
  

    
  
    
    

  

  

  


    












      

  
          

  
  

  
      @smichr
  smichr


        marked this pull request as ready for review

    October 1, 2023 15:31    
    









      

  
      



  

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        Oct 5, 2023


      
    


  





      


        



  
    

      
          
@asmeurer , what do you think about removing autoevaluation of log(x,i) as log(x)/log(i)?

      		
    

  





        


            

            
            

              
            

        

      


      

            
  
  

    
  
    
    

  

  

  


    












      

  
          
 
  

    
  

  



        @smichr
  smichr



        merged commit f327f0b
      into

      
  
    sympy:master
  


    Oct 11, 2023

  







  

  
  

  
      @smichr
  smichr


    
    deleted the
    
      
        log
    
    branch

    October 11, 2023 20:51    
    













  
  

    

      

  




      


    


    

      

        
      

  
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