Opened 13 years ago

Closed 12 years ago

# why the bit limit of 2^24 in RealField?

Reported by: Owned by: zimmerma AlexGhitza major sage-4.3.4 basic arithmetic sage-4.3.4.alpha0 François Maltey, Paul Zimmermann Alex Ghitza N/A

```sage: R = RealField(16777217)
---------------------------------------------------------------------------
ValueError                                Traceback (most recent call last)

/users/caramel/zimmerma/.sage/temp/patate.loria.fr/31828/_users_caramel_zimmerm\
a__sage_init_sage_0.py in <module>()

/usr/local/sage-core2/local/lib/python2.6/site-packages/sage/rings/real_mpfr.so\
in sage.rings.real_mpfr.RealField_constructor (sage/rings/real_mpfr.c:3723)()

/usr/local/sage-core2/local/lib/python2.6/site-packages/sage/rings/real_mpfr.so\
in sage.rings.real_mpfr.RealField.__init__ (sage/rings/real_mpfr.c:3945)()

ValueError: prec (=16777217) must be >= 2 and <= 16777216.
```

Note that 2^24 bits is only slightly above 5M digits, which is quite small (Fabrice Bellard recently computed 2700 billions of digits of Pi on a personal desktop, i.e., about 500,000 times more).

### comment:1 Changed 12 years ago by zimmerma

• Authors set to Francois Maltey and Paul Zimmermann
• Status changed from new to needs_review

The attached patch solves this problem, for example:

```sage: time a=n(pi,digits=10^7)
CPU times: user 113.52 s, sys: 0.22 s, total: 113.73 s
Wall time: 114.21 s
```

### comment:2 Changed 12 years ago by AlexGhitza

• Description modified (diff)

### comment:3 Changed 12 years ago by AlexGhitza

• Reviewers set to Alex Ghitza
• Status changed from needs_review to positive_review

Looks good and passes tests.

The referee patch adds a couple of doctests (bug fixes should be accompanied by doctests so that we don't regress again). The slightly weird "OverflowError?: ..." in the second test is due to the fact that the error messages are slightly different on 32-bit than on 64-bit machines.

### Changed 12 years ago by AlexGhitza

apply after the first patch

### comment:4 Changed 12 years ago by mvngu

• Authors changed from Francois Maltey and Paul Zimmermann to Francois Maltey, Paul Zimmermann
• Merged in set to sage-4.3.4.alpha0
• Resolution set to fixed
• Status changed from positive_review to closed

Merged in this order:

Paul: I merged trac_8157.patch, putting the ticket number in the commit message.

### comment:5 Changed 5 years ago by chapoton

• Authors changed from Francois Maltey, Paul Zimmermann to François Maltey, Paul Zimmermann

cedille

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