On Wednesday, January 21, 2015 at 10:56:29 AM UTC-8, Jon wrote:
>
> Hi all, I used the following code in notebook but it fails to give
> results. Any suggestions?
>
> var('a11,a12,a13,a14,a15,a16,a22,a23,a24,a25,a26,a33,a34,a35,a36,a44,a45,a46,a55,a56,a66,p,q,r',
>
> domain='real')
> g11=a11*p*p+a66*q*q+a55*r*r+2.0*a16*p*q+2.0*a15*p*r+2.0*a56*q*r;
> g22=a66*p*p+a22*q*q+a44*r*r+2.0*a26*p*q+2.0*a46*p*r+2.0*a24*q*r;
> g33=a55*p*p+a44*q*q+a33*r*r+2.0*a45*p*q+2.0*a35*p*r+2.0*a34*q*r;
> g12=a16*p*p+a26*q*q+a45*r*r+(a12+a66)*p*q+(a14+a56)*p*r+(a46+a25)*q*r;
>
> g13=a15*p*p+a46*q*q+a35*r*r+(a14+a56)*p*q+(a13+a55)*p*r+(a36+a45)*q*r;
>
> g23=a56*p*p+a24*q*q+a34*r*r+(a46+a25)*p*q+(a36+a45)*p*r+(a23+a44)*q*r;
>
> g0=matrix(3,3,[g11,g12,g13,g12,g22,g23,g13,g12,g33]).eigenvectors_right()
>
> It shows error "TypeError: ECL says: Memory limit reached. Please jump to
> an outer pointer, quit program and enlarge the memory limits before
> executing the program again." I have 9GB ram, and it fails before
> exhausting the ram.
>
Currently, maxima_calculus (the maxima instance that is used for some
symbolic calculations, apparently among which is the symbolic computation
of eigenvectors) has a memory limit of 1GB. You can lift that restriction
with the following command:
sage: maxima_calculus(1) #trigger the initialization of maxima
1
sage: from sage.libs.ecl import ecl_eval
sage: ecl_eval("(ext:set-limit 'ext:heap-size 0)")
<ECL: 0>
That said, I suspect doing so will just postpone failure, since the answer
you're asking likely doesn't fit in any computer. It tends to be true in
general that things that maxima is useful for tend to fit in a modest
amount of memory. So failing be default on a relatively low memory limit
gives early failure in cases that would likely fail anyway.
To get an idea of how big your answer likely is, you can estimate the
degree of the coefficients in the characteristic polynomial (3 times the
degree of the terms in the matrix) and count how many monomials in 24
variables of that degree exist. That gives you a ballpark number of term
you're likely asking maxima to work with.
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