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A PARI bug results in an unreliable prime_pi #3658

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sagetrac-fwclarke mannequin opened this issue Jul 15, 2008 · 6 comments
Closed

A PARI bug results in an unreliable prime_pi #3658

sagetrac-fwclarke mannequin opened this issue Jul 15, 2008 · 6 comments
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@craigcitro
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c: number theory p: minor / 4 t: bug
Milestone
sage-3.3

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@sagetrac-fwclarke
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sagetrac-fwclarke mannequin commented Jul 15, 2008 

----------------------------------------------------------------------
| SAGE Version 3.0.5, Release Date: 2008-07-11                       |
| Type notebook() for the GUI, and license() for information.        |
----------------------------------------------------------------------

sage: [prime_pi(n) for n in [500508..500510]]
[41580, 45056, 41581]
sage: [prime_pi(n) for n in [500508..500510]]
[41580, 41581, 41581]

The problem lies with pari/gp:

sage: %gp

  --> Switching to GP/PARI interpreter <-- 

''
gp: for(n=500508, 500510, print(primepi(n)))

41580
45056
  *** primepi: not enough precomputed primes, need primelimit ~ 500510.

Component: number theory

Issue created by migration from https://trac.sagemath.org/ticket/3658
@sagetrac-fwclarke sagetrac-fwclarke mannequin added this to the sage-3.4.1 milestone Jul 15, 2008
@craigcitro
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comment:1

The attached patch fixes the issue. This was a strange case -- in some cases, Pari is more than happy to return an (incorrect!) answer when you call primepi with a number larger than the prime limit. This patch fixes this in a uniform way.

@craigcitro craigcitro modified the milestones: sage-3.4.1, sage-3.3 Jan 23, 2009
@boothby
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boothby commented Jan 24, 2009

comment:3

works for me

@sagetrac-mabshoff
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sagetrac-mabshoff mannequin commented Jan 24, 2009

comment:4

On sage.math: oops:

sage -t -long "devel/sage/sage/libs/pari/gen.pyx"           
**********************************************************************
File "/scratch/mabshoff/sage-3.3.alpha2/devel/sage/sage/libs/pari/gen.pyx", line 7400:
    sage: pari._primelimit()
Expected:
    500000
Got:
    500519
**********************************************************************

Cheers,

Michael

@craigcitro
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Attachment: trac-3658.patch.gz

@craigcitro craigcitro changed the title A PARI bug results in an unreliable prime_pi [needs quick review] A PARI bug results in an unreliable prime_pi Jan 24, 2009
@boothby
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boothby commented Jan 24, 2009

comment:6

+1

@boothby boothby changed the title [needs quick review] A PARI bug results in an unreliable prime_pi A PARI bug results in an unreliable prime_pi Jan 24, 2009
@sagetrac-mabshoff
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sagetrac-mabshoff mannequin commented Jan 24, 2009

comment:7

Merged in Sage 3.3.alpha2.

Cheers,

Michael

@sagetrac-mabshoff sagetrac-mabshoff mannequin closed this as completed Jan 24, 2009
vbraun pushed a commit to vbraun/sage that referenced this issue Jun 16, 2024
sagemathgh-38209: Fix infinite loop bug in doctest from sagemath#36581
e65b8b8 
    
Discovered by tornaria [here](sagemath#3658
1/files/5c51f54b1a193c3f9964da3e1388efd87623d45c#r1575566025).

Sorry for the incorrect implementation! Please merge this quickly,
before the next beta (I think).
    
URL: sagemath#38209
Reported by: grhkm21
Reviewer(s): Travis Scrimshaw
vbraun pushed a commit to vbraun/sage that referenced this issue Jun 16, 2024
sagemathgh-38209: Fix infinite loop bug in doctest from sagemath#36581
6b93e0b 
    
Discovered by tornaria [here](sagemath#3658
1/files/5c51f54b1a193c3f9964da3e1388efd87623d45c#r1575566025).

Sorry for the incorrect implementation! Please merge this quickly,
before the next beta (I think).
    
URL: sagemath#38209
Reported by: grhkm21
Reviewer(s): Travis Scrimshaw
vbraun pushed a commit to vbraun/sage that referenced this issue Jun 17, 2024
sagemathgh-38209: Fix infinite loop bug in doctest from sagemath#36581
c8089eb 
    
Discovered by tornaria [here](sagemath#3658
1/files/5c51f54b1a193c3f9964da3e1388efd87623d45c#r1575566025).

Sorry for the incorrect implementation! Please merge this quickly,
before the next beta (I think).
    
URL: sagemath#38209
Reported by: grhkm21
Reviewer(s): Travis Scrimshaw
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