Tapas - Parallel Framework for Tree-based Adaptively PArtitioned Space

This software is released under the MIT License, see LICENSE.txt

How to build Tapas examples

Compiler Requirement

Tapas requires C++11 compiler. Recommended compiler versions are:

Compiler	Version
GNU C++ compiler	>= 4.9
LLVM clang++	>= 3.6
Intel C++ compiler	>= 2015

The FMM example

Basic compilation:

$ cd sample/exafmm-dev-13274dd4ac68/examples
$ mpicxx -std=c++11 -O2 -lrt tapas_exafmm.cxx -I../include -I../../../cpp/include -DUSE_MPI -DSpherical -DEXPANSION=10 -DFP64 -o parallel_tapas

• USE_MPI definition is for Tapas. MPI is not necessary for Tapas, but the current implementation does not support compiling without MPI and USE_MPI macro.
• Spherical, EXPANSION, and FP64 are definitions for TapasFMM, which is ExaFMM ported to Tapas.
  • Although the original ExaFMM supports Spherical and Cartesian kernels, but only Spherical is ported as of now. EXPANSION is degree of multipole/local expansion (typically 10). FP64 is to use double precision.

To build multithreaded code using MassiveThreads, add -DMTHREAD=1 and specify include/library path to your MassiveThreads installation.

$ MYTH_DIR=YOUR-MYTH-DIR
$ mpicxx (snip) -DMTHREAD=1 -I${MYTH_DIR}/include -L${MYTH_DIR}/lib -lmyth-native

Depending on how your MPI library is built, the mpicxx compiler may use its default compiler which does not support C++11. In such a case, you can speicfy the underlying C++ compiler via environment variables. See the documentation of the MPI for details.

$ # For mpich family (mpcih, mvapich, Intel MPI, etc.)
$ export MPICH_CXX="your new C++ compiler"

For advanced optimization with Intel Compiler,

$ mpicxx -std=c++11 -O2 -lrt tapas_exafmm.cxx -I../include -I../../../cpp/include -DUSE_MPI -DSpherical -DEXPANSION=10 -DFP64 -o parallel_tapas \
    -funroll-loops -xHOST -O3 -no-prec-div -fp-model fast=2 -no-inline-max-per-routine -no-inline-max-per-compile 

You may also want to inactivate debugging assertions:

$ mpicxx (snip) -DNDEBUG -DTAPAS_DEBUG=0

How to run:

$ mpiexec -np 10 ./parallel_tapas --numBodies 100000 --ncrit 64 --theta 0.34

• --nuBodies: Number of total bodies of the simulation (not number of bodies per process).
• --ncrit : Ncrit parameter of FMM (each leaf has at most Ncrit bodies)
• --theta : Multipole acceptance criteria

To control number of threads, use MYTH_WORKER_NUM environment variable for MassiveThreads.

Build FAQ

Q. I'm using new icpc/mpicxx but parallel_tapas doesn't compile. Why?

A. Check the version of g++. mpicxx uses g++ as a backend. If it's old, install a new gcc on your local environment (we recommend >= 4.9.3). By using mpicxx -show command, you can check what is the underlying C++ compiler is and how it is invoked. Also note that Intel C++ compiler uses GCC's standard library implementation directly. Thus if the system's default g++ is old, its STL is not C++11-ready.

Preprocessor symbols

Name	Possible values	Default value	Description
TAPAS_DEBUG	unset, 0, or 1	unset	Enable verbose debug output. Minor performance slowdown
TAPAS_DEBUG_DUMP	unset, 0, or 1	unset	Enable verbose debug output. Serious performance slowdown
TAPAS_REPORT_FILENAME	filename	unset	Performance report file name
TAPAS_REPORT_FORMAT	'csv' or 'fwf'	csv	File format of the report file (FWF or CSV)
TAPAS_REPORT_SEP	separator character	','	Separator character when CSV format is chosen
TAPAS_DEBUG_COMM_MATRIX	unset/any	unset	Print Communication Matrix in MPI_Alltoallv()
TAPAS_DEBUG_HISTOGRAM	unset/any	unset	Print depth histogram of the tree