mpmath doesn't work with python2.4

[certik]

ondra@fuji:~/ext/mpmath-svn$ python2.4
Python 2.4.5 (#2, Jun 25 2008, 14:11:58) 
[GCC 4.3.1] on linux2
Type "help", "copyright", "credits" or "license" for more information.

> > > import mpmath
> > > Traceback (most recent call last):
> > >   File "<stdin>", line 1, in ?
> > >   File "mpmath/**init**.py", line 5, in ?
> > >     from mptypes import *
> > >   File "mpmath/mptypes.py", line 18, in ?
> > >     from libmpc import *
> > >   File "mpmath/libmpc.py", line 342, in ?
> > >     alpha_crossover = from_float(1.5)
> > >   File "mpmath/lib.py", line 458, in from_float
> > >     return from_man_exp(int(m*(1<<53)), e-53, prec, rnd)
> > >   File "mpmath/lib.py", line 387, in from_man_exp
> > >     return normalize(sign, man, exp, bc, prec, rnd)
> > >   File "mpmath/lib.py", line 282, in _normalize
> > >     t = trailtable[man & 255]
> > > TypeError: list indices must be integers

Original issue for #89: http://code.google.com/p/mpmath/issues/detail?id=49

Original author: https://code.google.com/u/104039945248245758823/

Original owner: https://code.google.com/u/casevh/

[certik]

This is when 

man & 255 

is a gmpy's mpz. So it may as well be a bug in gmpy. Here is a fix that works:

# Index: mpmath/lib.py

--- mpmath/lib.py   ( revision 518 )
+++ mpmath/lib.py   (working copy)
@@ -279,13 +279,13 @@
         bc = prec
     # Strip trailing bits
     if not man & 1:
-        t = trailtable[man & 255]
-        t = trailtable[int(man & 255)]
       if not t:
           while not man & 255:
               man >>= 8
               exp += 8
               bc -= 8
-            t = trailtable[man & 255]
-            t = trailtable[int(man & 255)]
       man >>= t
       exp += t
       bc -= t
  @@ -373,7 +373,7 @@
       sign = 1
       man = -man
   if man < 1024:
-        bc = bctable[man]
-        bc = bctable[int(man)]
   else:
       bc = bitcount(man)
   if not prec:

**Status:** Started  

Original comment: http://code.google.com/p/mpmath/issues/detail?id=49#c1

Original author: https://code.google.com/u/104039945248245758823/

[fredrik-johansson]

I'd like to know how much slowdown this causes. An option would be to replace
trailtable and bctable by dicts if pyversion < 2.5 and gmpy-mode is used.

Original comment: http://code.google.com/p/mpmath/issues/detail?id=49#c2

Original author: https://code.google.com/u/111502149103757882156/

[certik]

Or just use this patch only for python < 2.5.  Slow mpmath is better than no mpmath.

Original comment: http://code.google.com/p/mpmath/issues/detail?id=49#c3

Original author: https://code.google.com/u/104039945248245758823/

[casevh]

The difference between Python 2.4 and 2.5 is that Python 2.5 uses the **index**
method when indexing a list. The **index** method was added in gmpy 1.02.

I used int() when I was testing the gmpy patches because I was using gmpy 1.01
originally. I inadvertently removed when I started testing with gmpy 1.03. 

I don't think using int() creates much of a slowdown.

Sorry about not testing under Python 2.4.

Original comment: http://code.google.com/p/mpmath/issues/detail?id=49#c4

Original author: https://code.google.com/u/casevh/

[casevh]

I'm working on a patch but it's not as easy as it seems. It wasn't difficult to add
int() to all the occurrences of bctable and trailtable. But while testing I've
encountered another subtle issue.

I've been assuming that the types of the components of an mpf are (int, MP_BASE, int,
int). But I've found at least one location where exp has type MP_BASE and a couple
other places where bc or exp is type long. I fixed the occurrence where exp has type
MP_BASE. I allowed bc and exp to become type long since I didn't think it was worth
the overhead.

I updated the test in -strict mode. It's easy to edit the tests to catch when bc and
exp are type long.

Original comment: http://code.google.com/p/mpmath/issues/detail?id=49#c5

Original author: https://code.google.com/u/casevh/

[certik]

Thanks for your work, now it works indeed. I'll update the mpmath in sympy.

Original comment: http://code.google.com/p/mpmath/issues/detail?id=49#c6

Original author: https://code.google.com/u/104039945248245758823/

[casevh]

Just closing the issue since Ondrej reports the problem is fixed.

**Status:** Fixed  
**Owner:** casevh  

Original comment: http://code.google.com/p/mpmath/issues/detail?id=49#c7

Original author: https://code.google.com/u/casevh/