On Dec 10, 5:20 am, "William Stein" <[EMAIL PROTECTED]> wrote:
> On Dec 9, 2007 8:01 PM, [EMAIL PROTECTED]
>
>
>
> <[EMAIL PROTECTED]> wrote:
>
> > I'm trying to use the combinatorics features in Sage to do some Chern
> > class calculations. When I run the commands below, I get exceptions
> > that I don't know how to interpret.
>
> > The same calculation in Maple using John Stembridge's SF package
> > completes successfully using roughly 149 MB and 7.08 s CPU time.
>
> > Is this just an issue of memory limitation? If so, can (and how do) I
> > lift the limitation to access more of the 2 GB I have on the machine
> > I'm running this on?
>
> > code follows:
> > I'm using Sage 2.8.15 on an i386 Linux platform. I also tried this on
> > an Intel OS X 10.5 machine with the same result. Also, all the powers
> > of "f" from 1 to 7 work fine. f^8 and higher powers fail.
> > -----------------------------------
>
> > sage: s=SFASchur(QQ)
> > sage: f=s([2,1]); f
> > s[2, 1]
> > sage: f^8
> > ---------------------------------------------------------------------------
> > <type 'exceptions.NotImplementedError'> Traceback (most recent call
> > last)
>
> > /Users/benjaminjones/Desktop/sage-2.8.15-osx10.5-intel-i386-Darwin/
> > <ipython console> in <module>()
>
> > /Users/benjaminjones/Desktop/sage-2.8.15-osx10.5-intel-i386-Darwin/
> > local/lib/python2.5/site-packages/sage/combinat/sfa.py in
> > __pow__(self, n)
> > 881 z = A(Integer(1))
> > 882 for i in range(n):
> > --> 883 z *= self
> > 884 return z
> > 885
>
> > /Users/benjaminjones/Desktop/sage-2.8.15-osx10.5-intel-i386-Darwin/
> > element.pyx in sage.structure.element.RingElement.__imul__()
>
> > .
> > .
> > .
> > .
>
> > /Users/benjaminjones/Desktop/sage-2.8.15-osx10.5-intel-i386-Darwin/
> > symmetrica.pxi in sage.libs.symmetrica.symmetrica._py()
>
> > <type 'exceptions.NotImplementedError'>: 22
> > sage:
>
> Mike Hansen -- who wrote the code you're using --
> will likely have to answer this question better than me. I suspect
> perhaps Symmetrica was compiled with certain hard-coded
> options set, and they were only set to allow up to something
> of "degree 7", i.e., this works:
>
> sage: s=SFASchur(QQ); f=s([2,1]); f
> s[2, 1]
> sage: time g=f^7
> CPU times: user 0.17 s, sys: 0.00 s, total: 0.17 s
> Wall time: 0.17
> sage: time g=f^6
> CPU times: user 0.07 s, sys: 0.00 s, total: 0.07 s
> Wall time: 0.07
> sage: time g=f^5
> CPU times: user 0.03 s, sys: 0.00 s, total: 0.03 s
> Wall time: 0.03
>
> Notice by the way that the time goes up by about 2.5 every
> time, so it would likely take about 0.42 seconds to do
> the calculation you want will likely be nearly 17 times
> faster in Sage than in John Stembridge's SF package
> one the above issue gets resolved.
>
> Important note: There is a brand new Symmetrica release
> (maybe 4 years in the making):
> http://trac.sagemath.org/sage_trac/ticket/1417
> This might fix the above issue, etc. I'm going to try
> that new spkg out along with the corresponding patch
> to see if it fixes the problem...
So numbers from 2.9.alpha3:
sage: time r=f^9
CPU times: user 0.98 s, sys: 0.01 s, total: 0.99 s
Wall time: 0.99
But at f^10 it fails again also with the new symmetrica.spkg. Mike:
any idea how to fix this?
>
> William
Cheers,
Michael
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