On 03/06/11 09:11, Anders Logg wrote: > On Fri, Jun 03, 2011 at 08:58:50AM +0100, Garth N. Wells wrote: >> >> >> On 02/06/11 18:05, Anders Logg wrote: >>> 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. >>> >> >> Have we reached the conclusion of removing the ODE solvers from >> lp:dolfin (for now)? > > Yes. >
Removed. Garth > -- > Anders _______________________________________________ Mailing list: https://launchpad.net/~dolfin Post to : dolfin@lists.launchpad.net Unsubscribe : https://launchpad.net/~dolfin More help : https://help.launchpad.net/ListHelp
