On Thu, Jun 02, 2011 at 04:49:23PM +0100, Garth N. Wells wrote: > > > On 02/06/11 13:41, Anders Logg wrote: > > Anyone using or interested in the ODE solvers should take a look > > below. > > > > On Thu, Jun 02, 2011 at 02:17:17PM +0200, Benjamin Kehlet wrote: > >> On 2 June 2011 14:02, Anders Logg <l...@simula.no> wrote: > >>> 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. > >> > >> I don't know of any solution to this. This is the same problem that we > >> discussed some months back (then related to Armadillo): Templated > >> libraries which rely on non-templated code (often old and implemented > >> i c), so they only support the types which these underlying libraries > >> can handle. I think the only solution here is a change in > >> boost::math::Legendre. > >> > >> Of course another solution would be to split the ODE solver from > >> Dolfin and let it continue as a separate project, and then import code > >> from that when we are going to look at automation/generating code for > >> time-dependent problems. > > > > Yes, perhaps it's time for that. Since it is going to be removed soon > > (and replaced by code generation), the best option might be to remove > > it before the release of 1.0. > > > > Are there any objections? Is anyone using the ODE solvers? > > > > No objection, I think that it's a good idea. > > Once the ODE solvers are out, we can re-design the arbitrary precision > interface.
Is there a need for high precision other than for the ODE solvers? There might be a need but I don't think it's being used anywhere except for in the ODE solvers. -- Anders > Garth > > > (They will make a comeback later in new form.) > > > _______________________________________________ Mailing list: https://launchpad.net/~dolfin Post to : dolfin@lists.launchpad.net Unsubscribe : https://launchpad.net/~dolfin More help : https://help.launchpad.net/ListHelp
