### » Submitted my first paper

August 4, 2021 at 15:30 | Adrian Kummerländer

Today I submitted the full paper of my talk at the 32nd ParCFD conference to the corresponding special issue of Computers & Fluids.

There we consider the LBM algorithm’s propagation step as a transformation of the space filling curve used as the memory bijection. Specifically, a neighborhood distance invariance property is utilized to derive the existing Shift-Swap-Streaming (SSS) scheme as well as a new Periodic Shift (PS) pattern.

A special focus is placed on SIMD friendly implementation via virtual memory mapping on both CPU and GPU targets.

Both patterns are evaluated in detailed benchmarks. PS is found to provide consistent bandwidth-related performance while imposing minimal restrictions on the collision implementation.

The preprint is available on Researchgate as well as directly (PDF).

### » Molecular Dynamics Simulation of the Benzene Dimer

March 31, 2021 at 20:05 | Adrian Kummerländer

One of the last lectures for my master’s degree was on numerical simulation in molecular dynamics. For the examination project I developed a GPU MD code capable of reproducing certain preferred configurations the benzene dimer.

### » Just-in-time volumetric CFD visualization

July 24, 2020 at 14:15 | Adrian Kummerländer

For my seminar talk I wrote another LBM solver as a literate Org-document using CUDA and SymPy. The main focus was on just-in-time volumetric visualizations of the simulations performed by this code. While this is not ready to publish yet, check out the following impressions:

Further videos are available on my YouTube channel. e.g. a Taylor-Couette flow:

### » Visualizing the velocity distribution of a hard sphere gas

March 24, 2020 at 21:42 | Adrian Kummerländer

The velocity distribution of a system of colliding hard sphere particles quickly evolves into the Maxwell-Boltzmann distribution. One example of this surprisingly quick process can be seen in the following video:

### » Visualize the sky for arbitrary time and space coordinates on earth

January 11, 2020 at 21:12 | firmament | 071bc3 | Adrian Kummerländer

The primary color of the sky is caused by Rayleigh and Mie scattering of light in the atmosphere. While attending the lecture on Mathematical Modelling and Simulation at KIT I implemented a ray marcher to visualize this. Together with a model for calculating the sun direction for given coordinates and times this allows for generating interesting plots:

For more details check out Firmament.

### » Started working on a framework for generating LBM kernels

October 27, 2019 at 22:35 | Adrian Kummerländer

During the past exam season I now and then continued to play around with my GPU LBM code symlbm_playground. While I mostly focused on generating various real-time visualizations using e.g. volumetric ray marching, the underlying principle of generating OpenCL kernels from a symbolic description has not lost its promise.

This is why I have now started to extract the generator part of this past project into a more general framework. Currently boltzgen targets C++ and OpenCL using a shared symbolic description while providing various configuration options:

λ ~/p/d/boltzgen (boltzgen-env) ● ./boltzgen.py --help
usage: boltzgen.py [-h] --lattice LATTICE --layout LAYOUT --precision
PRECISION --geometry GEOMETRY --tau TAU [--disable-cse]
[--functions FUNCTIONS [FUNCTIONS ...]]
[--extras EXTRAS [EXTRAS ...]]
language

Generate LBM kernels in various languages using a symbolic description.

positional arguments:
language              Target language (currently either "cl" or "cpp")

optional arguments:
-h, --help            show this help message and exit
--lattice LATTICE     Lattice type (D2Q9, D3Q7, D3Q19, D3Q27)
--layout LAYOUT       Memory layout ("AOS" or "SOA")
--precision PRECISION
Floating precision ("single" or "double")
--geometry GEOMETRY   Size of the block geometry ("x:y(:z)")
--tau TAU             BGK relaxation time
--disable-cse         Disable common subexpression elimination
--functions FUNCTIONS [FUNCTIONS ...]
Function templates to be generated
--extras EXTRAS [EXTRAS ...]