Concatenation of HealSparse Files¶
HealSparse contains a routine for concatenating (combining) multiple
HealSparseMap files. If
fitsio is available, this will be done in a memory-efficient way. In this way, multiple non-overlapping maps can be combined. This makes possible a simple parallelized scatter-gather approach to creating complex survey maps, where individual tiles are run independently, and then all combined at the end.
cat_healsparse_files() routine takes in a list of filename, and an output filename. The individual files must have the same
nside_sparse, but may have different
nside_coverage. The output file will have the same
nside_coverage as the first input file unless otherwise specified.
By default, for speed, the code will not check that the input
HealSparseMap files are non-overlapping (that is, that they do not share
valid_pixels; they may share coverage in the coverage map). This can be checked.
fitsio is available (recommended), the combination is not done in-memory. This behavior can be modified by the user by setting
True. However, if only
astropy.io.fits is available for FITS interfacing, the concatenation can only be done in-memory (and the
in_memory value should be overridden.
import healsparse healsparse.cat_healsparse_files(file_list, outfile, check_overlap=False, clobber=False, in_memory=False, nside_coverage_out=None)