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Daniel Shapero
@danshapero

Hi all -- I'm looking at how to differentiate expressions involving IndexedBase objects. When I run the following code:

import sympy
n = sympy.symbols('n', integer=True)
M = sympy.IndexedBase('M', shape=(n, n))
x = sympy.IndexedBase('x', shape=n)
i = sympy.Idx('i', n)
j = sympy.Idx('j', n)
k = sympy.Idx('k', n)
energy = 0.5 * M[i, j] * x[i] * x[j]
print(sympy.simplify(energy.diff(x[k])))

I get an expression involving lots of Kronecker deltas. I feel it should be possible to simplify these out but I don't know how. Thoughts?

Maq_Owais
@MaqOwais
@MaqOwais
Sir, as I came to know that ' Handling modular equations ' already integrated with _solveset then why it showed
in gsoc project under solvers module?
do we again have to reintegrate under _transolve ?
and remove that part from _solveset ? to have a reply : )
OmarWagih1
@OmarWagih1
Hello All, i just posted my application on the github wiki for some reviews and comments, could you please look at it? Would very much appreciate it. Thanks!
https://github.com/sympy/sympy/wiki/GSoC-2020-Application-Omar-Wagih:-Benchmarks-and-performance
Hello All, i just posted my application on the github wiki for some reviews and comments, could you please look at it? Would very much appreciate it. Thanks!
Gagandeep Singh
@czgdp1807
@Arpan612
Yes sir, I saw it now. I will do it.
@czgdp1807 Could you please tell me who are the potential mentors for symengine project?
Saanidhya
@Saanidhyavats
I have made the changes in pr #18681. It would be helpful if someone could review it
@Arpan612
@Saanidhyavats Could you please go through my proposal and suggest changes?
I am reviewing your changes. I will put up my comments on Github.
Saanidhya
@Saanidhyavats
Sure
BasileiosKal
@BasileiosKal
Hi all! I have made the changes the reviewer's proposed in my pr #18875. Could you please review it?
Mohit Balwani
@Mohitbalwani26
In my PR #18881 travis has already passed on when i checked on travis offcial websote but it is showing still pending in GitHub. What could be the reason?
mohit
@mohitacecode
Hello Arpan,
I have left comment on the issue.
mohit
@mohitacecode
the files mentioned in the issues are already created you have to identify the test in test_matrices.py and test_commonmatrix.py and move them to their related test file. for example all the solvers related test should be transferred to test_solvers.py.
just a opinion the discussion related to pr should be kept there.I will also post the previous comment there.
Saanidhya
@Saanidhyavats
I have made a pr #18932, it would be helpful if someone could guide me further on it
@Arpan612
I am on it.
Julian
@cod3monk
Is there a simple way to find and divide all terms of relationals by the gcd, if one exists?
This should turn 64*M*N - 104*N - 56 <= 11796480 into 8*M*N - 13*N - 7 <= 1474560. simplify does not do the trick.
mohit
@mohitacecode
maybe something like this.
>>> a = 64*M*N - 104*N - 56 - 11796480 <= 0
>>> factor(a)
8*(8*M*N - 13*N - 1474567) <= 0
@cod3monk
Stefan Corneliu Petrea
sss
Aaron Meurer
@asmeurer
@danshapero how should it simplify?
Daniel Shapero
@danshapero
@asmeurer the result I get is
>>> 0.5*(KroneckerDelta(i, k)*x[j] + KroneckerDelta(j, k)*x[i])*M[i, j]
which mathematically I know to be equal to 0.5 * (M[k, j] * x[j] + M[i, k] * x[i]) at the very least
of course I haven't put in any assumptions about M being self-adjoint so I'm not expecting anything there
Aaron Meurer
@asmeurer
oh I see it simplifies when you expand it
I'm not sure if there is code in sympy to simplify deltas like this yet.
it's possible there is and I am just not finding it
I would open an issue about it
Daniel Shapero
@danshapero
ok, thanks!
@Arpan612
@asmeurer Does travis ci bulid fail when we have unused imports?
Smit Lunagariya
@Smit-create
Yes, it does.
Unused imports as well as for unused variables too.
@Arpan612
Thanks!
Saanidhya
@Saanidhyavats
I have made some changes in pr #18681and made a new pr #18947, if someone could look at both of them then it would be really helpful
S.Y. Lee
@sylee957
@asmeurer Why does all PRs cannot be merged even if they pass the tests? Is there any problem with the bots?
Moses Paul R
@iammosespaulr
@sylee957 if you're referring to #18947 ... I don't think it passed the tests
  tests finished: 4675 passed, 1 failed, 183 skipped, 127 expected to fail,

1 expected to fail but passed, in 1238.67 seconds

DO *NOT* COMMIT!
btw ... Hi everyone !! ... I'm Moses and I'm new here :smile:
@Arpan612
Moses Paul R
@iammosespaulr
Thanks @Arpan612 !!
@Arpan612
Anytime.