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. > > -- > Anders > > >> 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. 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
