SANEPIC

Installation

mpic++ and fftw3 are need for the installation. The code can be compiled with the following:

make ARCH=<target>

where target comes from the file names Makefiles/Make.target.

Example: To compile on Origin cluster, use make ARCH=OR after importing necessary modules.

Running SANEPIC

Since SANEPIC requires a bunch of input files to run and it produces some files, it is better if we organize the input files and outputs. For the sake of convenience, consider making the following directory tree anywhere in you system:

test_dir
├── bolo_info
│   ├── bolometer_info.txt
│   └── iSpf<fknee>_<fsample>_index<index>__<detector_name>
├── out_dir
├── pointings_list
│   ├── pointings_dec.bi
│   ├── pointings_psi.bi
│   └── pointings_ra.bi
├── segments
│   └── segment_list_12_256.bi
└── tod_list
    └── data_<detector_name>output.bi

The files in this directory tree are following:

1. bolometer_info.txt

   This file contains the information about the detectors. I don't know what information the first three columns contain, but the fourth column is the detector orientation angle, the fifth is the name of the telescope (LFT, MFT, HFT) and the last column is the detector name. The detector name defined here must be used to replace the detector_name in the files below.

2. iSpf<fknee>_<fsample>_index<index>__<detector_name>

   This binary file contains the noise power spectrum. fknee, fsample and index must be replaced with the $f_{knee}$, $f_{sample}$ and power index respectively of the $1/f$ spectrum.

3. pointings_dec.bi

   This binary file contains the declination angle (colatitude) of the detector pointing. Note that this file name is generic (not related to a detector). Be careful when you are using multiple detectors for map-making. Same applies to the three files below.

4. pointings_ra.bi

   This binary file contains the right ascension angle (longitude) of the detector pointing.

5. pointings_psi.bi

   This binary file contains the polarization angle associated with the pointing.

   [!NOTE] SANEPIC and litebird_sim use different angle conventions for colatitude and longitude:

   	litebird_sim	SANEPIC
   Dec (colatitude) range	$(0, \pi]$	$(-\pi/2, \pi/2]$
   RA (longitude) range	$(-\pi, \pi]$	$(0, 2\pi]$
   psi (detector orientation angle)	$(-\pi, \pi]$	$(-\pi, \pi]$

6. segment_list_<nn>_<seglength>.bi

   This binary file contains segmentation information. It tells SANEPIC in how many chunks the TOD and pointing files must be read from the disk and distributed among the MPI processes (To be verified). The product of nn and seglength must be at least the length of TOD. This file can be produced with helpers/generate_segfile.c code. It can be compiled with gcc generate_segfile.c -o generate_segfile.x and used as ./generate_segfile.x [filename] [number of segments] [seglength].

7. data_<detector_name>output.bi

   This binary file contains the detector TOD.

To run SANEPIC with the input files, one can use the script ./scripts/run_sanepic.sh provided in this repository. Before running the script, make sure to update the following variables:

• nprocs: The number of MPI slots to be used
• base_dir: The path of the base directory. In this case, it the path that contains the directory tree shown above.
• fknee: $f_{knee}$ of the $1/f$ spectrum. It must be same as in the file available in the directory tree.
• fsamp2: $f_{sample}$ of the $1/f$ spectrum. It must be same as in the file available in the directory tree.
• indexN: Power index of the $1/f$ spectrum. It must be same as in the file available in the directory tree.
• NSIDE: $N_{nside}$ of the output maps.
• fsamp: $f_{samp}$ of the TOD.
• det_num: Number of detectors to be used in map-making.
• det_name: Name of the detector to be used in map-making. The information of the corresponding detector must be available in the bolometer_info.txt file.
• pol: Set this to 1 if you want to produced the polarization maps. Set it to 0 otherwise.
• nn: Number of chunks in which TOD must be divided. See segment_list_<nn>_<seglength>.bi above.
• seglength: Length of each TOD chunks. See segment_list_<nn>_<seglength>.bi above.
• hwp_status: Set this to 1 if you want to use HWP modulated signal. Set it to 0 otherwise.
• OmegaHWPsamp: Doesn't do anything tbh.

Once all the input files have been prepared and parameters are updated in the shell script, one can simply run SANEPIC with

bash run_sanepic.sh

SANEPIC outputs

SANEPIC produces bunch of outputs files in binary format. With the shell script provided in this repo, the output files are stored in out_dir. Typically the following files will be produced:

map__A_output_N<nside>_.bin_1
map__COS2P_output_N<nside>_.bin
map__HITSoutput_N<nside>_.bin
map__I_output_N<nside>_.bin_1
map__NVARoutput_N<nside>_.bin
map__POL_HITSoutput_N<nside>_.bin
map__Q_NVARoutput_N<nside>_.bin
map__Q_output_N<nside>_.bin_1
map__SIN2P_output_N<nside>_.bin
map__U_NVARoutput_N<nside>_.bin
map__U_output_N<nside>_.bin_1

One can use the python script helpers/plot_sanepic_maps.py to plot all the output maps at once. The script must be run as

python plot_sanepic_maps.py <base_dir> <nside>