Opened 6 years ago
Last modified 21 months ago
#17903 new defect
Wrong approximation for taylor series of L-series for elliptic curves on 32 bits architecture.
Reported by: | tmonteil | Owned by: | |
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Priority: | major | Milestone: | sage-6.6 |
Component: | elliptic curves | Keywords: | sdl |
Cc: | Merged in: | ||
Authors: | Reviewers: | ||
Report Upstream: | N/A | Work issues: | |
Branch: | Commit: | ||
Dependencies: | Stopgaps: |
Description (last modified by )
On 32-bits systems, #16997 introduces the following behaviour:
sage: L = EllipticCurve('37a').lseries() sage: L.taylor_series(10) 0.990010459847588 + 0.0191338632530789*z - 0.0197489006172923*z^2 + 0.0137240085327618*z^3 - 0.00703880791607153*z^4 + 0.00280906165766519*z^5 + O(z^6)
Which is very far from the value before #16997 (which stay unchanged on 64 bits architecture).
Note the following gap when increasing the precision by 1 bit (at 54 bits, the value coincides with the one before #16997):
sage: L.taylor_series(10, prec=53) 0.990010459847588 + 0.0191338632530789*z - 0.0197489006172923*z^2 + 0.0137240085327618*z^3 - 0.00703880791607153*z^4 + 0.00280906165766519*z^5 + O(z^6) sage: L.taylor_series(10, prec=54) 0.997997869801216 + 0.00140712894524909*z - 0.000498127610959923*z^2 + 0.000118835596665833*z^3 - 0.0000215906522442074*z^4 + (3.20363155415891e-6)*z^5 + O(z^6)
Direct evaluation leads to the same problem:
sage: L.dokchitser(prec=53)(10) 0.990010459847588 sage: L.dokchitser(prec=54)(10) 0.997997869801216
Change History (3)
comment:1 Changed 6 years ago by
- Description modified (diff)
comment:2 Changed 6 years ago by
comment:3 Changed 21 months ago by
- Keywords sdl added
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Did you do an upstream report to pari and/or Tim Dokchitser?