Contribution before GSoC

Organization : SymPy
Solvers: Completing Solveset

Sept 2015 -June 2016

by Shekhar Prasad Rajak — Posted on April 24, 2016

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SymPy :

SymPy is a Python library for symbolic mathematics. It aims to become a full-featured Computer Algebra System (CAS) while keeping the code as simple as possible in order to be comprehensible and easily extensible.

It was month of August 2015, when I was learning new libraries in python and somehow reached at Amit’s blog about SymPy and his contribution to SymPy. I am very much interested in Mathematics so it was pretty amazing to see how SymPy is solving equations and doing mathematics using python.

Joined gitter chat room :

The time I joined SymPy gitter chat room, I found many active contributors/developers replying the questions and discussing ideas. I didn’t know how SymPy works and didn’t work in Python previously. I started reading Documentations and Wiki Pages present in SymPy repository in github. I watched the videos and tried some problems myself, but doing only these things would not help. I started participating in gitter chat discussion, give answer whatever I knew and questioned whenever I had doubts. These became my everyday work. Slowly I understood the modules and code organization of SymPy.But there were still something I didn’t know, that’s why I was not able to send any patches/Pull Request in github SymPy repo till Nov-Dec 2015.

Started sending Pull Request

I had been active in SymPy gitter chat room for around 3 month but still struggling to fix a bug. I tried most of the easy bugs but didn’t understand where is the problem in the code.

So I started fixing Documentation bugs and formating. But I wanted to fix bugs related to code.

One day someone was discussing about debugger tool. He was also getting difficulty in understanding the code. I read some articles and started using PuDB.

PuDB works very well and easy to work with it. I restarted exploring the easy bugs and using debugger it was pretty easy to detect the line where the problem was.

Contribution started now

Okay, so after learning these many thing I was very much interested about SymPy, because I almost understood how the Open Source Developers work. I enjoyed my days fixing/trying to fix bugs in SymPy. All the day I think about the bug and try to solve them. I enjoyed a lot in this period. It was around Dec 2015 ,Jan 2016.

Merged/Open/Closed contributions in chronological order before GSoC 2016

#10215 : some Usage/examples for srepr and added some lines to show how repr different from srepr printing.

#10311 : Projects using SymPy in docs.

#10312 : #10215 extended and added more usage/examples for srepr.

#10314 : Dot printing examples and usage.

#10319 : Addition of namespaces, namespaces_default, translation for SciPy in lambdify.py.

#10330 : removal of guide.rst.

#10333 : better comment at SymPy/interactive/tests/test_print_builtin_option.

#10370 : math.fabs() converts its argument to float if it can (if it can’t, it throws an exception). It then takes the absolute value, and returns the result as a float. Fixes #9474

#10385 :SymPy treated symbols having zero = True assumption as non-negative & non-positive & real. But SymPy don’t know; that is 0.It was not defined anywhere in SymPy. Previously line x = Symbol('x' ,zero=True), x was treated as symbol only, during execution and didn’t took its value. Fixes #8167

#10407 : In NumPyamin is defined as numpy.amin(a, axis=None, out=None, keepdims=False) So if we use Min and Numpy is installed in the system. Then SymPy use NumPy for lambdify method. So when we pass l(1, 2, 3) Then it takes ` a =1 ,axis=2,out=3 where a is list of numbers for which we want minimum. SymPy mapping with NumPy amin` is not correct.

#10444 : Integration of summation type expressions. Fixes #7827

#10460 : Solveset is now able to solve XFAIL test_issue_failing_pow. assert solveset(x**(S(3)/2) + 4, x, S.Reals) == S.EmptySet.

#10482 : This is able to give solutions in reduced/simplified and known easy form in many cases. Fixes #9824 , #10426

#10494 : Few lines added in docs for Singleton S.

#10502 : Needed a list which stores about if particular cond solution is added or not. Otherwise it may not add result , like previously if cond solution is not added but still [if condition] true (for this particular issue’s testcase) and then it will mark matches_other_piece = True so this solution couldn’t be added into result. Fixes #10122

#10542 : Need to pass if integral have symbolic upper and lower bound. Fixes : #10434

#10547 : Problem was Solveset assuming that condition symbol is same as symbol for which it is finding solution. so there was problem when condition doesn’t contains the solution symbol. Now is storing the symbols of condition and defining the interval accordingly for all the symbols. Fixes : #10534

#10550 : solveset_real need to check symbol in piecewise-condition.Expression with multiple abs ,having Piecewise solution as 0. Fixes : #10122 and #10534

#10552 :Solveset hyperbolic Functions.

#  complex solution
>>>> solveset(sinh(x))
{n⋅ⅈ⋅π | n∊ ℤ}
# Real solution
>>>> solveset(sinh(x), x, S.Reals)
{0}

Fixes #9531 , #9824 , #10426, #7914 and #9606

#10575 : linsolve now able to solve unsimplified equations having constant variable. Fixes : #10568

#10579: modified domain range if denominator is zero. Fixes #8715

#10622 : Decompogen checking whether function contains symbol or not.

#10649: replacing solver in some module.

#10689: Real solution for some const**(symbol) type equation. Fixes Real solution for #10688

#10713: Proposing a method to get general form for list of args.

#10733: Rewriting #10552 and #10482 with extensions. Fixes #10671 , #7914 , #9531 , #9606 , #9824 , #10426 , #10217 and most of the XFAIL present in test_solveset.

#10764: TODO part of #10733 Fixes XFAIL test-cases and #7914

#10898: Implementing the logic of #10713 in solve_trigmethod insolveset. This PR is able to give simplified solution for trigonometric equation. Example :

>>>>>print solveset(cos(x) +cos(3*x) + cos(5*x), x, S.Reals)
ImageSet(Lambda(_n, _n*pi/6),Integers())

#10971 Fixes [#10864]((https://github.com/sympy/sympy/issues/10864) Old solver have ` _tsolve to solve transcendental equation, but in solveset _invert method can handle some works of the _tsolve` method. One of them could be:

x =symbols('x' , positive = True)</span>
solveset(x**(y*z) - x,x,S.Reals)</span>

#10994 Now solveset returns Integers solution for an equation using diophantine.py .

>>> solveset(2*x + 3*y - 5, x, S.Integers)
{(3⋅t₀ - 5, -2⋅t₀ + 5) | t₀ ∊ ℤ}
>> solveset(2*x + 3*y - 5, domain=S.Integers)
{(3⋅t₀="" -="" 5,="" -2⋅t₀="" +="" 5)="" |="" t₀="" ∊="" ℤ}

#11008 Fixes #10876

Bugs/issues reported

  • #10033 : Wrong answer by Inequality solver.
  • #10313 : Need good description about Dot printing.
  • #10453 : Integrate return wrong answer (inverse trigonometric functions).
  • #10568 : linsolve Returns EmptySet if equation is not simplified.
  • #10688 : Not able to solve some const**(symbol) type equation.
  • #10864 : solveset(x**(y*z) - x, x, S.Reals) returns ConditionSet`.

Getting ready to choose a Project

As I am too much excited to work for SymPy all the time. Jan 2016 I started preparing the GSoC proposal. After these contribution the another major part was choosing a project and getting idea to improve certain module in SymPy.Then I started working on Project for the GSoC proposal.

You can read about my Project in this blog : GSoC 2016 Project



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