Empty delta_E array if ring.momentum single valued

[scpalbright]

If the ring is created with a single value for momentum the ring.delta_E array is empty. This causes problems anywhere that delta_E is used. I would propose that in this case it should also be single valued and 0.

It's caused by the calculating of delta_E, which for 0 turns enters the else statement in this block (lines 369-373):

if (self.n_turns+1) > len(self.use_turns):
    self.delta_E = np.zeros(self.energy.shape)
    self._recalc_delta_E()
else:
    self.delta_E = np.diff(self.energy, axis=1)

I would propose the changing this block to:

if (self.n_turns+1) > len(self.use_turns):
    self.delta_E = np.zeros(self.energy.shape)
    self._recalc_delta_E()
elif self.n_turns > 0:
    self.delta_E = np.diff(self.energy, axis=1)
else:
    self.delta_E = np.zeros(self.energy.shape)

[alasheen]

For me this would be fine.

In BLonD the default behavior for single valued momentum would be:

• automatically extend it to have 2 identical values (corresponding to n_turns=1 and len(momentum)==n_turns+1)
• then the delta_E would be single valued.

I would maybe ask what should be the general rule for len(delta_E) when a 'single valued vs. turn based vs. time based' momentum program is passed ? And how do we expect it to be calculated when the program is time based ?

[scpalbright]

As in momentum = [[0], [2E9]], so time based but single valued?