#6803 closed enhancement (fixed)
Implement symbolic Kronecker delta and also make current signum (sgn) symbolic
| Reported by: | gmhossain | Owned by: | |
|---|---|---|---|
| Priority: | major | Milestone: | sage-4.3 |
| Component: | symbolics | Keywords: | |
| Cc: | Merged in: | sage-4.3.alpha0 | |
| Authors: | Golam Mortuza Hossain | Reviewers: | Karl-Dieter Crisman |
| Report Upstream: | N/A | Work issues: | |
| Branch: | Commit: | ||
| Dependencies: | Stopgaps: |
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Description (last modified by )
We should have a symbolic Kronecker delta in Sage.
Also, current implementation of signum (sgn) function returns wrong answer for symbolic input.
sage: sgn(x) 1 sage: sgn(-x) 1
So we should make sgn() symbolic aware. Given, implementation of these functions in new symbolics should be very similar to the existing generalized function Dirac delta and Heaviside, I am putting them together here.
Also, ticket #777 should be closed down as Sign is already in Sage and this ticket will further enhance it.
Patch:
Apart from implementing these two symbolic functions, attached patch slightly speeds up three other generalized functions by avoiding default __call__ method of PrimitiveFunction?. These functions take explicit value either 0,-1,1 so those checks are not needed.
Timing before the patches:
sage: timeit('dirac_delta(1.0)')
625 loops, best of 3: 179 µs per loop
sage: timeit('unit_step(1.0)')
625 loops, best of 3: 345 µs per loop
sage: timeit('heaviside(1.0)')
625 loops, best of 3: 344 µs per loop
Timing after the patches:
sage: timeit('dirac_delta(1.0)')
625 loops, best of 3: 159 µs per loop
sage: timeit('heaviside(1.0)')
625 loops, best of 3: 324 µs per loop
sage: timeit('unit_step(1.0)')
625 loops, best of 3: 323 µs per loop
Also, it does slight re-arrangements of references.
Attachments (3)
Change History (10)
Changed 13 years ago by
comment:1 Changed 13 years ago by
- Description modified (diff)
- Summary changed from Implement symbolic Kronecker delta and also make current signum (sgn) symbolic to [with patch, needs review] Implement symbolic Kronecker delta and also make current signum (sgn) symbolic
comment:2 Changed 13 years ago by
- Milestone set to sage-4.1.2
- Reviewers set to Karl-Dieter Crisman
- Summary changed from [with patch, needs review] Implement symbolic Kronecker delta and also make current signum (sgn) symbolic to [with patch, needs work] Implement symbolic Kronecker delta and also make current signum (sgn) symbolic
comment:3 Changed 13 years ago by
- Status changed from needs_work to needs_review
- Summary changed from [with patch, needs work] Implement symbolic Kronecker delta and also make current signum (sgn) symbolic to Implement symbolic Kronecker delta and also make current signum (sgn) symbolic
I have attached the patch, but with the random test fixed as a reviewer patch. Apply only this patch.
comment:4 Changed 13 years ago by
- Status changed from needs_review to positive_review
comment:5 follow-up: ↓ 6 Changed 13 years ago by
- Merged in set to sage-4.3.alpha0
- Resolution set to fixed
- Status changed from positive_review to closed
I had to add a small patch to the doctest for sage.quadratic_forms.extras.sgn to make sure that the doctest was actually doctesting that function.
comment:6 in reply to: ↑ 5 ; follow-up: ↓ 7 Changed 13 years ago by
Replying to mhansen:
I had to add a small patch to the doctest for sage.quadratic_forms.extras.sgn to make sure that the doctest was actually doctesting that function.
Can you post that here, or at least the code in braces - just for posterity?
comment:7 in reply to: ↑ 6 Changed 13 years ago by
- Report Upstream set to N/A
Replying to kcrisman:
Can you post that here, or at least the code in braces - just for posterity?
mhansen's patch is contained in trac_6803-sgn.patch
Overall this is good, and should get positive review. However, there is a doctest failure (very typical when one adds a new symbolic function in line 204 of symbolic/random_tests.py, with random_expr(). This should be easy to fix.