[Users] McLachlan help

[James Healy]

Hi Erik,

We evolve alpha and beta for the gauge variables as given in equations 
7a and 7b of http://arxiv.org/pdf/1506.06153.pdf.  The number I reported 
for LazEv was using 5th order dissipation applied to all 21 evolved 
variables (alp, beta^i, At_{ij}, gt_{ij}, Gammat^{i}, trK, and xi).

LazEv is calculating the Hamiltonian and Momentum constraints as well as 
the constraints on Gammat^i using 4th order stencils.

I also forgot to mention that I did these tests on 16 nodes, and the 
memory usage was relatively low ( ~2 GB/MPI process ).

I will give the internal dissipation for McLachlan a try.

Thanks,
Jim

On 07/27/2015 05:56 PM, Erik Schnetter wrote:
> Jim
>
> Thanks for posting the details.
>
> Can you give us more details about the LazEv scheme? In particular 
> there may be differences in the gauge. What (gauge) variables do you 
> evolve? What gauge conditions do you use? And what kind of dissipation 
> do you apply? Can you point us to the source code?
>
> For the new McLachlan, you would probably use the built-in dissipation 
> instead of thorn Dissipation, which should lead to a small speed-up.
>
> -erik
>
> On Mon, Jul 27, 2015 at 4:43 PM, James Healy <jchsma at rit.edu 
> <mailto:jchsma at rit.edu>> wrote:
>
>     Hello,
>
>     I have been running some tests on Stampede comparing the run speed
>     of McLachlan to RIT's evolution thorn LazEv.  I started with the
>     qc0-mclachlan.par parameter file included with the Einstein
>     Toolkit, added a few refinement levels, increased the resolution
>     and changed McLachlan to be 8th order (and increased the number of
>     ghost zones to 5).  I also increased the initial separation so the
>     finest grids aren't already overlapping.  To compare with LazEv, I
>     removed the McLachlan and Dissipation thorns and replaced them
>     with LazEv. Everything else in the parameter file is exactly the
>     same.  I tried using both the McLachlan master and rewrite branches.
>
>     The grid setup is 10 levels of refinement, dx=4M on the coarsest
>     with outer boundary at 400M, M/128 on the finest with r=0.6M, CFL
>     is 0.25.  Both use 8th order spatial differencing with
>     ghost_size=5 and 5th order dissipation.
>
>     Below is a summary of the results as reported at iteration 256
>     from Carpet::physical_time_per_hour:
>
>     McLachlan - rewrite branch: 3.0596110 M/hr
>     McLachlan - master branch: 3.8033607 M/hr
>     LazEv - 4.1941544 M/hr
>
>     I am using the stampede-impi.cfg configuration file in simfactory.
>     "module list" returns:
>
>       1) TACC-paths   3) cluster-paths      5) xalt/0.4.6   7) TACC
>       2) Linux        4) intel/13.0.2.146 <http://13.0.2.146>  6)
>     cluster      8) impi/4.1.0.030 <http://4.1.0.030>
>
>     Attached is my parameter file.  I pasted the McLachlan parameters
>     below.  Are there any optimizations that I can use for McLachlan?
>     Are the parameters I am using for it what would be used for
>     production runs?
>
>     ML_BSSN::harmonicN           = 1      # 1+log
>     ML_BSSN::harmonicF           = 2.0    # 1+log
>     ML_BSSN::ShiftGammaCoeff     = 0.75
>     ML_BSSN::BetaDriver          = 1.0
>     ML_BSSN::LapseAdvectionCoeff = 1.0
>     ML_BSSN::ShiftAdvectionCoeff = 1.0
>
>     ML_BSSN::MinimumLapse        = 1.0e-8
>
>     ML_BSSN::my_initial_boundary_condition = "extrapolate-gammas"
>     ML_BSSN::my_rhs_boundary_condition     = "NewRad"
>     Boundary::radpower                     = 2
>
>     ML_BSSN::ML_log_confac_bound = "none"
>     ML_BSSN::ML_metric_bound     = "none"
>     ML_BSSN::ML_Gamma_bound      = "none"
>     ML_BSSN::ML_trace_curv_bound = "none"
>     ML_BSSN::ML_curv_bound       = "none"
>     ML_BSSN::ML_lapse_bound      = "none"
>     ML_BSSN::ML_dtlapse_bound    = "none"
>     ML_BSSN::ML_shift_bound      = "none"
>     ML_BSSN::ML_dtshift_bound    = "none"
>
>     ML_BSSN::fdOrder = 8
>
>     ActiveThorns = "Dissipation"
>
>     Dissipation::order = 5
>     Dissipation::vars  = "
>             ML_BSSN::ML_metric
>             ML_BSSN::ML_trace_curv
>             ML_BSSN::ML_curv
>             ML_BSSN::ML_Gamma
>             ML_BSSN::ML_lapse
>             ML_BSSN::ML_shift
>             ML_BSSN::ML_dtlapse
>             ML_BSSN::ML_dtshift
>     "
>
>     ActiveThorns = "ML_ADMConstraints"
>
>
>     Thanks,
>     Jim Healy
>
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>
>
> -- 
> Erik Schnetter <schnetter at cct.lsu.edu <mailto:schnetter at cct.lsu.edu>>
> http://www.perimeterinstitute.ca/personal/eschnetter/

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