/demotrack_cuda

Specialized C++/CUDA version of demotrack

Primary LanguageC++MIT LicenseMIT

demotrack_cuda

Specialized C++/CUDA version of demotrack.

Overview

Implements a minimal particle tracking software for beam-dynamics studies, similar to what sixtracklib or simpletrack provide. It only implements the bare minimum of necessary beam-elements and infrastructure and is not suitable for production use!

Requirements:

  • CUDA 8.x or newer (C++11 as kernel language is required)
  • cmake >= 3.11
  • gcc or clang suitable for C++11 enabled CUDA

Build instructions

Normally, cloning this repository, creating a build directory, running cmake from the build directory and then make should be sufficient to build the demos:

git clone https://github.com/martinschwinzerl/demotrack_cuda.git
cd demotrack_cuda
mkdir build
cd build
cmake ..
make

Usage Examples

A) Simple FODO lattice To run demo01_sc0 with 102400 particles for 100 turns on the default simplified FODO lattice and with default initial conditions for the particles, use

cd build
./demo01_sc0 102400 100

Note: the same signature applies to the other demox_scy applications unless otherwise noted B) LHC lattice with no beam-beam interaction but with imperfections Same number of particles and turns as with the previous exampleas, but now both the particles and the lattice are loaded from prepared binary files provided in the data subdirectory of this repository:

cd build
./demo01_sc0 102400 100 ../data/lhc_no_bb_particles.bin ../data/lhc_no_bb_lattice.bin

Note: Again, the same signature applies to the other demox_scy applications unless otherwise noted

C) Creating a binary file with initial particle state If you want to run a specific lattice with a different initial particle distribution, tools/create_particle_data could be useful. It allows to generate a set of NUM_PARTICLES and allows to linearly / uniformly distribute the x, y, px, py, zeta, and deltaattributes:

cd build/tools
./create_particle_data 

Usage: create_particle_data PATH_TO_PARTICLE_DATA_DUMP NUM_PARTICLES P0C MASS0 [CHARGE0]
            [MIN_X]    [MAX_X]    [MIN_Y]     [MAX_Y]
            [MIN_PX]   [MAX_PX]   [MIN_PY]    [MAX_PY]
            [MIN_ZETA] [MAX_ZETA] [MIN_DELTA] [MAX_DELTA]

The output path PATH_TO_PARTICLE_DATA, the number of particles NUM_PARTICLES, the kinetic energy and rest mass of the reference particle P0C and MASS0 respectively are mandatory parameters (both given in units of eV). The reference particle charge CHARGE0 defaults to a proton, i.e. 1 and is expressed as multiples of the elementary charge.

All other lengths (i.e. x, y, zeta) are given metres and default to 0. The relative transversal momenta (px, py) are given in radians and default to 0. The relative momenta deviation delta is a unit-less ratio and defaults to 0.

All command line parameters to create_particle_data are positional, i.e. in order to only change one of the later sets of parameters, one has to provide values for all the previous ones as well. MIN_* / MAX_* parameters have to given pairwise, e.g. providing only one is not sufficient.

In order to create an initial particle distribution of 1024 protons at 6.5 TeV and a spread in zeta from 0.0 to 1e-3, one would run the tool as follows:

cd build
tools/create_particle_data ../data/lhc_particles.bin 1024 6.5e12 938.272081e6 1.0 \
    0.0 0.0 0.0 0.0 \
    0.0 0.0 0.0 0.0 \
    0.0 1e-3 0.0 0.0

TODO: Provide a python tool with a more convenient interface / calling convention!

List of demo / example files

  • demo01.cu: Implements a naive implementation of tracking (i.e. particles stored in global memory, lattice stored in global memory, straight-forward implementation of the tracking logic). The tracking kernel is inside demo01.cu. It uses a minimal FODO lattice with only 8 elements in the following arrangement:

    • A Multipole in a dipole configuration dipole0
    • A Drift drift0 with a length of 5m
    • A Multipole in a focusing quadrupole configuration q0
    • A Drift drift1 with a length of 5m
    • A Multipole in a dipole configuration dipole1
    • A Drift drift2 with a length of 5m
    • A Multipole in a de-focusing quadrupole configuration q1
    • A Drift drift3 with a length of 5m
    • A Cavity cavity0 with a voltage of 5000000V, a frequency of 239833966 Hz and a lag of 180 deg

    Please cf. the file lattice.h for details. The default particle beam for the FODO lattice consists of protons with a kinetic energy of 470 GeV. Two executables are generated from demo01.cu:

    • demo01_sc0: space-charge / beam-fields are disabled
    • demo01_sc1: space-charge / beam-fields are enabled

  • demo02.cu: Similar to demo01.cu but now a thread-local copy of the particle data is used for tracking over all turns rather than always hitting the global memory.

List of infrastructure / library files

  • CMakeLists.txt build configuration and setup file. Edit to enable different compiler flags, architectures, etc.
  • definitions.h typedefs and definitions to abstract away different platforms
  • config.hgenerated header file controlling the calculation of the grid dimensions or using a predefined value
  • particle.h provides the particle model and auxiliary functions
  • beam_elements.h provides models for the beam-elements, e.g. Drift, DriftExact, Multipole, Cavity, XYShift, SRotation
  • beamfields.h implementation of space charge / beam field elements like SpaceChargeCoasting
  • lattice.h setup the simple lattice, infrastructure for loading pre-assembled lattices from binary files