ParMETIS is a parallel version of METIS and can be used as an alternative to
ptScotch or Zoltan, supporting multi-constraints and redistribution:
Description
ParMetis redistribution in parallel
Note: parMetis methods do not support serial operation.
Parameters
- Method of decomposition
- kWay: multilevel k-way
- geomKway: combined coordinate-based and multi-level k-way
- adaptiveRepart: balances the work load of a graph
- Options
- options[0]: The specified options are used if options[0] = 1
- options[1]: Specifies the level of information to be returned during
the execution of the algorithm. Timing information can be obtained by
setting this to 1. Additional options for this parameter can be obtained
by looking at parmetis.h. Default: 0.
- options[2]: Random number seed for the routine
- options[3]: Specifies whether the sub-domains and processors are coupled
or un-coupled. If the number of sub-domains desired (i.e., nparts) and
the number of processors that are being used is not the same, then these
must be un-coupled. However, if nparts equals the number of processors,
these can either be coupled or de-coupled. If sub-domains and processors
are coupled, then the initial partitioning will be obtained implicitly
from the graph distribution. However, if sub-domains are un-coupled from
processors, then the initial partitioning needs to be obtained from the
initial values assigned to the part array.
- itr: Parameter which describes the ratio of inter-processor communication
time compared to data redistribution time. Should be set between 0.000001
and 1000000.0. If set high, a repartitioning with a low edge-cut will be
computed. If it is set low, a repartitioning that requires little data
redistribution will be computed. Good values for this parameter can be
obtained by dividing inter-processor communication time by data
redistribution time. Otherwise, a value of 1000.0 is recommended.
Default: 1000.
The ParMETIS sources can be downloaded and compiled in ThirdParty-dev using the
link in the README file and the compilation commands in Allwmake.
Note the specific license under which ParMETIS is released:
Copyright & License Notice
--------------------------
The ParMETIS package is copyrighted by the Regents of the
University of Minnesota. It can be freely used for educational and
research purposes by non-profit institutions and US government
agencies only. Other organizations are allowed to use ParMETIS
only for evaluation purposes, and any further uses will require prior
approval. The software may not be sold or redistributed without prior
approval. One may make copies of the software for their use provided
that the copies, are not sold or distributed, are used under the same
terms and conditions.
As unestablished research software, this code is provided on an
``as is'' basis without warranty of any kind, either expressed or
implied. The downloading, or executing any part of this software
constitutes an implicit agreement to these terms. These terms and
conditions are subject to change at any time without prior notice.
Optional CPU load caching can be switched-on for Lagrangian cloud tracking
and/or chemistry integration using the new cpuLoad switch in the cloudProperties
or chemistryProperties dictionary files respectively and used for
multi-constraint load-balancing by the fvMeshDistributorsLoadBalancer specified
in the dynamicMeshDict file
distributor
{
type loadBalancer;
libs ("libfvMeshDistributors.so");
multiConstraint true;
redistributionInterval 10;
}
which used the distributor specified in the decomposeParDict file, e.g.
numberOfSubdomains 12;
decomposer simple;
distributor zoltan;
libs ("libzoltanDecomp.so");
simpleCoeffs
{
n (2 2 3);
}
zoltanCoeffs
{
lb_method rcb;
}
The incompressibleDenseParticleFluid/cyclone case has been updated to
demonstrate this new functionality and shows a speedup ~50% using the Zoltan RCB
multi-constraint distributor. The multicomponentFluid/counterFlowFlame2D_GRI
case has also been updated to use the new cpuLoad switch.
The alpha equation in this model has been changed to a d2dt2 scheme,
rather than a hard-coded correction on a ddt scheme that relies on the
old-time value remaining unchanged from the previous timestep. This
modification makes the model compatible with some forms of mesh change.
The 'featureAngle' control defines the included angle between faces
above which layer extrusion is prevented. Its use within snappyHexMesh
was incorrect in that the cosine was not being taken before being
compared to dot products of face normals. This has now been corrected.
Existing 'featureAngle' settings may need changing to recover equivalent
behaviour. Any angle previously set to 58 degrees or above previously
resulted in no reduction of layer coverage. A large angle between 90 and
180 degrees is likely to be an appropriate replacement for cases such as
this. Angles previously set to 57 degrees and below can be equivalently
replaced by a value of (180/pi)*arccos(<angle>*(pi/180)).
Note that changing the feature angle also affects the slip feature
angle. The slip feature angle is taken to be half the feature angle if a
'slipFeatureAngle' is not specified.
The parcelsPerSecond control can now be specified as a time-varying
function. This provides additional control over the temporal
distribution of injected parcels, which may be advantageous if, for
example, the mass flow rate varies significantly. It also enables
variable flow rates of particulates in cases which have a fixed number
of particles per parcel.
