Add flags for non-monotonic eccentricity and it's first derivative

[a-ravichandran]

The following changes are suggested add flag variables to indicate if the eccentricity and it's first derivative are non-monotonic:

1. Declare flag variables here.

        # Setting non monotonic ecc flag to False by default        
        self.ecc_is_nonmonotonic = False
        # Setting positivity decc_dt flag to False by default
        self.decc_dt_is_positive = False

2. Assign flag variables here.

        if any(self.decc_dt_for_checks > 0):
            idx = np.where(self.decc_dt_for_checks > 0)[0]
            range = self.get_range_from_indices(idx, self.t_for_checks)
            message = ("egw(t) is nonmonotonic "
                       f"{'at' if len(idx) == 1 else 'in the range'} {range}")
            self.ecc_is_nonmonotonic = True
            debug_message(message, self.debug_level,
                          point_to_verbose_output=True)

        # Is ecc(t) a convex function? That is, is the second
        # derivative always negative?
        if check_convexity:
            self.d2ecc_dt_for_checks = self.derivative_of_eccentricity(
                self.t_for_checks, n=2)
            if any(self.d2ecc_dt_for_checks > 0):
                idx = np.where(self.d2ecc_dt_for_checks > 0)[0]
                range = self.get_range_from_indices(idx, self.t_for_checks)
                message = ("Second derivative of egw(t) is positive "
                           f"{'at' if len(idx) == 1 else 'in the range'} "
                           f"{range}")
                self.decc_dt_is_positive = True
                debug_message(f"{message} expected to be always negative",
                              self.debug_level,
                              point_to_verbose_output=True)

[md-arif-shaikh]

Thanks @a-ravichandran! I am trying to understand what is the use case of these flags given that one can simply use check_monotonicity_and_convexity to get these information from the gwecc_object.

[a-ravichandran]

Hi @md-arif-shaikh. When measure_eccentricity() is called, the non-monotonicity and convexity checks automatically happen, so rerunning the function separately might not be the optimal choice. The use-case of this is that in the surrogate_modeling repo, when working with eccentric waveforms, the piece of script that measures the eccentricity, if it is non-monotonic (likely due to presence of junk), the script is automated to iteratively discard portions of the waveform before recomputing eccentricity. And this process is repeated until the eccentricity becomes monotonic. This requires the presence of those flags in the gwecc_object.

[md-arif-shaikh]

Okay. Unless the call to gwecc_object.check_monotonicity_and_convexity is too expensive for your use case, I am not seeing a compelling reason to add those flags. Ideally, self should include variables that are mostly used in other methods defined inside the object. @vijayvarma392 what do you think?