Leave sign of 0 unspecified for tanh `inf + yj`
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Assessment
- Difficulty
- 2/5
- Estimated time
- 1-3 hours
- Newbie friendliness
- 70/100
- Issue type
- Documentation
- Clarity
- Mostly clear
- Activity status
- Quiet
- Domain
- documentation
Research direction
Start at the tanh complex special-cases section linked in the issue and compare its +infinity + iy wording with the cited ctanh specification. Update the requirement so it does not mandate a positive signed zero, then verify that the array API special-case tests and the dpnp failure are consistent with the revised wording.
Written by the indexing model from the issue text.
Description
The array API spec states, for tanh complex special cases
If a is +infinity and b is a positive (i.e., greater than 0) finite number, the result is 1 + 0j
from open-std pages describing ctanh
— ctanh(+∞ + iy) returns 1 + i0sin(2y), for positive-signed finite y.
This matches up to the math (we can derive this from tanh(x + iy) taking the limit as x approaches infinity and constraining y to be finite), and gives us 1 ± 0i, with the sign being inherited from sin(2y) if we care about signed zeros, rather than positive zero in all cases.
This was brought up because this special case is tested by the array API tests, which causes dpnp to fail the test.
- Dominant language
- Python
- Stars
- 281
- Forks
- 52
- PR merge metrics
- No merged PRs in 30d
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