CMBLensing-SPT3G Interface

Install

The root folder of this repo is both a Julia package and a Python package. To install both, clone this repo,

git clone https://github.com/SouthPoleTelescope/CMBLensingSPT3GInterface

then from the Julia package prompt run:

pkg> dev /path/to/CMBLensingSPT3GInterface

and add the folder to your PYTHONPATH:

export PYTHONPATH=/path/to/CMBLensingSPT3GInterface:$PYTHONPATH

This last step may also be done in a Python session with

import sys; sys.path = ["/path/to/CMBLensingSPT3GInterface"] + sys.path

If you added the interface to a specific Julia project, you will also have to make sure that Python knows to use the correct project environment:

import os; os.environ["JULIA_PROJECT"] = "/path/to/project"

These steps must be done before importing the interface.

You will need a working build of spt3g_software. Conversely, CMBLensing.jl will get installed automatically by the dev command above if you don't have it.

Usage

This package makes it so any fields passed between Julia and Python are automatically converted between the corresponding CMBLensing.jl and spt3g_software types, and all unit conversions and Fourier convention differences are automatically handled. This mapping currently includes:

CMBLensing.jl	spt3g_software
FlatMap	FlatSkyMap
FlatFourier	MapSpectrum2D
FlatIEBFourier	MapSpectraTEB
Anything else	dict

This means, for example, you can create a FlatSkyMap in Python and pass it to Julia, where it arrives as a FlatMap, or create a FlatMap in Julia and pass it to Python, where it arrives as a FlatSkyMap.

Julia Example

julia> using CMBLensingSPT3GInterface

julia> py"""
       import numpy as np
       from spt3g.maps import FlatSkyMap, MapProjection
       from spt3g.core import G3Units
       """
       
julia> f = py"FlatSkyMap(np.random.rand(10,10), res=2*G3Units.arcmin, proj=MapProjection.ProjZEA)"
100-element FlatMap{10×10 map, 2′ pixels, fourier∂, Array{Float64,2}}:
...

julia> py"type($f)"
PyObject <class 'spt3g.maps.FlatSkyMap'>

Python Example

In [1]: from CMBLensingSPT3GInterface import jl

In [2]: f = jl("FlatMap(rand(10,10))"); f
Out[2]: <spt3g.maps.FlatSkyMap at 0x7f7f370d2c30>

In [3]: jl("typeof($f)") 
Out[3]: <PyCall.jlwrap FlatMap{10×10 map, 1′ pixels, fourier∂, Array{Float64,2}}>

Units

CMBLensing.jl fields do not currently track their units. By default, the conversion always assumes that these fields are in μK units, and Fourier transforms are in 1/μK units. If instead the field is unitless (for the example, if the field represents a mask whose values may lie between 0 and 1), wrap the field in unitless before conversion, e.g.:

python> jl("unitless(FlatMap(rand(10,10)))")
<spt3g.maps.FlatSkyMap at 0x7fee41d26180>

In the other direction, spt3g_software fields do track their units (in FlatSkyMap.units), so no such manual wrapper like unitless is needed.

Notes

Map Orientation

CMBLensing.plot() defaults to origin="upper" which will result in maps flipped in the $y$ direction compared to plotting tools in spt3g_software, which default to origin="lower". Pass origin="lower" to CMBLensing.plot() to make CMBLensing use the 3g software convention."