X-BACH (Extended Basic Accelerated C++ HOTPANTS) is an astronomical image subtraction software created by Gustav Arneving and Hugo Wilhelmsson, as part of a master's thesis conducted at MindRoad Öst AB. It is based on BACH, an earlier master's thesis by Annie Wång and Victor Lells.
X-BACH is a parallelization of the popular image subtraction tool HOTPANTS, rewritten in C++, and using OpenCL for task acceleration. It operates on two FITS images, one called science and one called template, generates a difference image by subtraction. The purpose of X-BACH was to explore the parallelization potential of non-trivial parallelizable tasks in the HOTPANTS algorithm and check how it would perform.
See here.
The usage of X-BACH is highlighted below:
BACH -t <template image name> -s <science image name>
X-BACH also supports some optional arguments. These arguments are presented below:
-o <convolved output name>: name of the convolved output FITS image. Defaults todiff.fits.-op <output path>: name of the output folder, where the output images will be stored. Defaults toout/.-ip <input path>: name of the input folder, where the input images are located. Defaults tores/.-v: turns on verbose mode.-vt: prints execution time.-p <int>: integer to choose which platform to use. Platforms are listed when in verbose mode. Defaults to0.-d <int>: integer to choose which device to use. Devices are listed when in verbose mode. Defaults to0.-sss <mp|cl>: use openmp or opencl to compute Stamp and SubStamps. Defaults tomp.
For instance, if the input files are stored in C:\in, called science.fits and template.fits, and the output files would be written to C:\out, the following command would be used:
BACH -t template.fits -s science.fits -ip "C:\in\" -op "C:\out\"
This would generate two files, diff.fits (convolved image) and sub.fits (subtracted image) in C:\out.
- Input and output path arguments are glitchy. Always put '/' (or '\') at the end of the path.
- Non-deterministic behaviour is observed between computers in some rare test cases.