cvvcv 2010/7/13 8fjm39j <dfrie...@gmail.com> > Following up with another data point: > > Sage 4.3.4 under some version of Redhat Linux on an intel computer > with 64GB RAM. > > The case that failed on the 4GB macbookpro succeeds here: minimize() > returns a value. > > A larger case fails in the same manner, minimize() returning without > a value: > S is a polynomial over Q in 48 variables > S is a quartic polynomial > S contains 71138 terms. > > Daniel Friedan > > On Jul 13, 1:07 pm, 8fjm39j <dfrie...@gmail.com> wrote: > > I am trying to minimize numerically (over the reals) a polynomial S > > with rational coefficients. > > > > The function sage.numerical.optimize.minimize() returns without > > returning a value. > > > > Here's the relevant fragment of Sage code (executed using the menu > > item 'evaluate all') > > > > ===== BEGIN CODE FRAGMENT ===================================== > > > > N > > 44 > > > > # RQ = PolynomialRing(QQ, N, 'x', sparse=True); # this was executed > > earlier > > > > S in RQ > > True > > > > print 'S is a polynomial over Q in', len(S.variables()), 'variables'; > > print 'S is a quartic polynomial'; > > print 'S contains', len(S.coefficients()), 'terms'; > > S is a polynomial over Q in 44 variables > > S is a quartic polynomial > > S contains 55188 terms > > > > S_exp =SR(S); > > init_values = [0] * len(S_exp.variables()); > > soln=sage.numerical.optimize.minimize(S_exp,init_values); > > soln > > Traceback (click to the left of this block for traceback) > > ... > > NameError: name 'soln' is not defined > > > > ===== END OF CODE FRAGMENT ===================================== > > > > This does not happen for a smaller problem: > > S is a polynomial over Q in 40 variables > > S is a quartic polynomial > > S contains 34766 terms > > i.e., minimize() does successfully return a value. > > > > I'm running Sage Version 4.4.4 under OS X 10.6.4 on a macbookpro with > > 4GB RAM, acquired in the form > > sage-4.4.4-OSX-64bit-10.6-i386-Darwin.dmg > > > > I would attach the worksheet itself to this posting, if I saw a way to > > do so. > > > > Any help would be much appreciated. Also any pointers towards a more > > efficient method to minimize such polynomials. I'm just starting to > > learn Sage and Python. At the moment, the bottlenecks appear to be > > the conversion to a symbolic expression, 'S_exp =SR(S); ' and the > > execution of minimize(). The polynomial algebra used to construct S > > executes relatively quickly. The number of variables is of the form > > N=4mn where m and n are positive integers. I'd like to take N slightly > > larger, though I don't expect that my computing resources will allow > > taking N much larger, even if I use a more efficient method to > > minimize S. > > > > thanks, > > Daniel Friedan > > -- > To post to this group, send email to sage-support@googlegroups.com > To unsubscribe from this group, send email to > sage-support+unsubscr...@googlegroups.com<sage-support%2bunsubscr...@googlegroups.com> > For more options, visit this group at > http://groups.google.com/group/sage-support > URL: http://www.sagemath.org >
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