1. Usage

1.1 Installation

There are two things that need to happen before a raw git clone of this repo will run:

1. Compile all of the C files in the C_libs folder, and
2. Create an empty directory called logs in the main pipeline repo (this one is just a bug)

   bash C_libs/setup.sh
   mkdir logs
   

1.2 Command-line usage and argparse

l2gen.py uses argparse for arguments (run python3 l2gen.py --help for all options, or have a look in the l2gen_argparse.py file). Example usage:

python l2gen.py --obsid_start 10000 --runlist my_runlist.txt --write_inter_files True

However, it's easier to add these parameters to a parameter file, using the following syntax:

python l2gen.py --params param_file.txt

Example of a file containing the same three parameters as above (sadly no comments allowed):

--obsid_start 10000
--runlist my_runlist.txt
--write_inter_files True

1.3 MPI

l2gen.py support MPI, in the excepted way:

mpirun -n 16 python l2gen.py --param param_file.txt

The memory requirement is about 2-3 times the size of a scan, per process.

To run on multiple nodes, use machinefiles, in the usual way:

mpirun --machinefile machinefile.txt python l2gen.py --param param_file.txt

machinefile.txt looking like:

owl18:16
owl19:16
owl20:16

2. Code and Development

2.1 Code overview

• l2gen.py - The main code. Contains the class l2gen_runner, which reads the parameters and runlist, spawns MPI processes, and creates a series of instances of the l2gen class, each processing a single scan.
• l2gen_argparse.py - File containing all argparsing. Imported by the l2gen_runner class.
• l2gen_l2class - Contains the level2_file class, which is the data object holding all level2 data. It also reads level1 files from disk, and writes level2 files to disk.
• l2gen_filters.py - The file where all the filters used by the l2gen class are stored. These filters take a level2_file class object as input, and modifies it in different ways.

2.2 Creating a new filter

...

2.3 Generating a simulation cube

import l2_simulations as sims
from l2gen_argparser import parser

# read in default parameters
params = parser.parse_args()
# probably want to change:
params.sim_npix_x = 120 # number of pixels in the output map, in the angular x direction (RA)
params.sim_npix_y = 120 # number of pixels in the output map, in the angular y direction (Dec)
params.sim_nmaps = 1024 # number of frequency channels in the output map
params.sim_output_dir = './simulations' # directory in which to save the output simulation files

# set up generator object
simgen = sims.SimGenerator(params)

# run
simgen.run()

3. TODO

• Signal injection simulation filter: Filter which reads a simulation cube, and insertes it into the TOD.
• PCA optimizations: Currently using SKLearn PCA filter, which isn't parallelized. Want a Ctypes module which calculates and removes a single PCA component.
• Adaptive number of PCA modes: Instead of a static number of PCA modes, calculate and remove modes until some criteria is reached (eigenvalue threshold, probably).
• Finish frequency filter: The implemented frequency filter does not seem to be working optimally, and some debuging is required.