#7539: primes.p0.spkg with "prime_sieve.c" functionality
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Reporter: GeorgSWeber | Owner: rohana
Type: enhancement | Status: new
Priority: major | Milestone: sage-4.3.1
Component: number theory | Keywords:
Work_issues: | Author: rohana, GeorgSWeber
Upstream: N/A | Reviewer:
Merged: |
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Comment(by leif):
WARNING: Do not use the current version of "Silva.c" to count primes in
intervals beyond approx. 18302910352e9 (assuming a sieve segment size of
2MB, i.e. _sieve_bits_log2_=24; with lower segment sizes, overflows occur
later).
Unfortunately, these early overflows do not lead to run-time errors (e.g.
segmentation faults) but unsuspiciously wrong results.
["Obvious" (run-time) errors do occur much later due to other overflow
conditions.]
Note also that you currently must not use 1 as the interval's upper bound
or (little worse) 2 as its lower bound, because prime counts will be wrong
by one (1 is treated as prime while 2 is not).
Nevertheless, Happy New Decade...
-Leif
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Ticket URL: <http://trac.sagemath.org/sage_trac/ticket/7539#comment:9>
Sage <http://www.sagemath.org>
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