Previously IFOComboMap was indexed as [single detector, two detectors, three detectors, ...]. This means that checking to see how many and which detectors are in use can't be easily done without referring back to the table, and any changes to the table can potentially break other parts of the code.
This pull request changes IFOComboMap to be indexed by powers of two. That
means that any index of (2^i - 1) is a single detector, indicated by
index into IFOMap. Now when using IFOComboMap, the number of detectors
in use can be determined using
__builtin_popcount(icombo + 1), and
whether a single detector is in use can be done with the check
index & (icombo + 1).
Additionally, every possible combination of existing IFO was outputted as
a part of the XML dump from
cohfar. This meant that the size of the
XML dump wasn't tied to the actual number of IFOs in use, and would
continue to exponentially increase in size as we increased the number of
IFOs that might be in play (e.g. KAGRA, LIGO-India, etc.).
To solve this, we have moved to using the total combination (as an index
into IFOComboMap) as a store of the active IFOs, and using
__builtin_popcount() to get the total number of IFOs that are in use
in that combination. This means that we can quickly and efficiently
determine the maximum number of detectors that we actually need to print
stats for, with no additional information required.
Passes trigger comparison test.