subroutine mask2scan( mask, pixelization, scan)
Purpose:
Allocates and defines the S2HAT scandef structure, scan, corresponding to a observed
sky patch defined by a mask, mask.
It can be called by all procs or only by one proc root and followed by a call to mpi_scanbcast.
The structure scan has to be defined on all procs prior to a call to any of the transform.
Parameters:
input:
- mask- [integer(4b)], a vector of the full map length (=pixelization%npixsall) with 0 and 1 defining the observed sky patch (=1);
- pixelization- [pixeltype], a S2HAT structure defining all the properties of the pixelization;
output:
- scan- [scandef], a S2HAT structure containing all the info about the cut-sky needed by the transforms.
N.B.1 Note that on the input to s2hat_map2alm routines the unobserved pixels should be explicitly masked out by setting
their values to zero. On the output of the s2hat_alm2map routines one should explicitly mask the pixels which were not
observed.
N.B.2 Currently the optimization is available only for the two general types of the masks:
- singly-connected sky patches;
- two sky patches each of which is singly-connected, e.g., the nearly full sky with the galaxy cut and points sources removed.
For more complicated masks, the s2hat routines should NOT used directly but rather the mask should be simplified to comply with
the requrements listed above. All the other features will be still correctly included (if set to zero as described above) just the computation
will not be directly optimized to account on their presence.
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