On Thu, Jun 02, 2011 at 01:10:01PM +0200, Benjamin Kehlet wrote: > On 2 June 2011 11:51, Anders Logg <l...@simula.no> wrote: > > On Thu, Jun 02, 2011 at 10:46:29AM +0100, Garth N. Wells wrote: > >> > >> > >> On 02/06/11 10:26, Anders Logg wrote: > >> > On Thu, Jun 02, 2011 at 10:07:59AM +0100, Garth N. Wells wrote: > >> >> > >> >> > >> >> On 01/06/11 23:46, Anders Logg wrote: > >> >>> Have you checked that there is no performance penalty? > >> >> > >> >> I just have - evaluating a Legendgre polynomial 10k times at the same > >> >> point is just noise with both methods (of the order 10^-5 - 10^-4 s). > >> > > >> > It may be noise for some applications, but not for others. I'm not > >> > sure this is a bottle-neck for the ODE code (Benjamin will know) but > >> > we need to evaluate Legendre polynomials of degree > 100 many times > >> > and then it may not be noise. > >> > > >> > >> For very high degree (e.g. 200) Boost is marginally faster. > > > > Sounds promising then. > > > >> >> The Boost code is slightly slower because it doesn't cache the values > >> >> (which is nice not to do), but may be faster if the call is inlined. > >> >> It's not possible to inline it at the moment because of clashes between > >> >> tr1:tuple and boost::tuple (Boost bug, I suspect). Old and new are the > >> >> same when evaluating at different points. > >> > > >> > Let's wait for Benjamin to comment. > >> > > >> > >> The speed is about the same (with scope to improve the speed for Boost) > >> for unique values. The caller should be responsible for caching, if > >> desired, since it can lead to memory blow out. > >> > >> Legendre does not appear in the ode code. It only appears in the > >> computation of quadrature schemes. > > > > True, but the quadrature schemes are used in the ode code. > > > > > > > >> Garth > >> > >> > >> > >> >> Garth > >> >> > >> >> > >> >>> Benjamin has > >> >>> worked quite hard on optimizing some of the basic math routines (in > >> >>> some cases by many many orders of magnitude). > >> >>> > >> >>> Benjamin, can you take a look that it still works? > > Yes, the performance seems to be about the same, but I'm unable to > compile it with support for GMP. > > /usr/include/boost/math/special_functions/legendre.hpp:178: > instantiated from ‘typename boost::math::tools::promote_args<RT, > float, float, float, float, float>::type boost::math::legendre_p(int, > int, T, const Policy&) [with T = __gmp_expr<__mpf_struct [1], > __mpf_struct [1]>, Policy = > boost::math::policies::policy<boost::math::policies::default_policy, > boost::math::policies::default_policy, > boost::math::policies::default_policy, > boost::math::policies::default_policy, > boost::math::policies::default_policy, > boost::math::policies::default_policy, > boost::math::policies::default_policy, > boost::math::policies::default_policy, > boost::math::policies::default_policy, > boost::math::policies::default_policy, > boost::math::policies::default_policy, > boost::math::policies::default_policy, > boost::math::policies::default_policy>]’ > /usr/include/boost/math/special_functions/legendre.hpp:185: > instantiated from ‘typename boost::math::tools::promote_args<RT, > float, float, float, float, float>::type boost::math::legendre_p(int, > int, T) [with T = __gmp_expr<__mpf_struct [1], __mpf_struct [1]>]’ > /home/benjamik/fenics/dolfin-wells_gmp/dolfin/math/Legendre.cpp:42: > instantiated from here > /usr/include/boost/math/special_functions/legendre.hpp:167: error: no > matching function for call to ‘pow(__gmp_expr<__mpf_struct [1], > __gmp_binary_expr<long int, __gmp_expr<__mpf_struct [1], > __gmp_binary_expr<__gmp_expr<__mpf_struct [1], __mpf_struct [1]>, > __gmp_expr<__mpf_struct [1], __mpf_struct [1]>, > __gmp_binary_multiplies> >, __gmp_binary_minus> >, > __gmp_expr<__mpf_struct [1], __gmp_binary_expr<__gmp_expr<__mpf_struct > [1], __mpf_struct [1]>, long int, __gmp_binary_divides> >)’ > /usr/include/bits/mathcalls.h:154: note: candidates are: double > pow(double, double) > /usr/include/c++/4.4/cmath:358: note: float > std::pow(float, float) > /usr/include/c++/4.4/cmath:362: note: long double > std::pow(long double, long double) > /usr/include/c++/4.4/cmath:369: note: double > std::pow(double, int) > /usr/include/c++/4.4/cmath:373: note: float std::pow(float, > int) > /usr/include/c++/4.4/cmath:377: note: long double > std::pow(long double, int) > [...] > > boost::math::legendre seems to rely on std::pow which is not > templated, only implemented with the most common types.
If it's not possible to make it work, we need to revert back. -- Anders > Benjamin > > >> >>> > >> >> > >> >> _______________________________________________ > >> >> Mailing list: https://launchpad.net/~dolfin > >> >> Post to : dolfin@lists.launchpad.net > >> >> Unsubscribe : https://launchpad.net/~dolfin > >> >> More help : https://help.launchpad.net/ListHelp > > > > _______________________________________________ > > Mailing list: https://launchpad.net/~dolfin > > Post to : dolfin@lists.launchpad.net > > Unsubscribe : https://launchpad.net/~dolfin > > More help : https://help.launchpad.net/ListHelp > > _______________________________________________ Mailing list: https://launchpad.net/~dolfin Post to : dolfin@lists.launchpad.net Unsubscribe : https://launchpad.net/~dolfin More help : https://help.launchpad.net/ListHelp
