Constant EARLY_FAILURE_LOSS 

pub(super) const EARLY_FAILURE_LOSS: f64 = _; // 0.002f64

The loss beyond which a complete sum below every automatic split fails early, while its real-space terms still add up.

The loss is relative to the scale of a component of the sum at the automatic split, as cancellation counts it. The failure comes before the far shells, where the Kambe series of the terms grow with 1 / eta^2. The predicted loss only grows with the terms, so the complete sum would fail too unless it came back more than a scale off the automatic one. The automatic sum (the jet, for a jet) is evaluated once, where a loss exceeds this of 1 for the value or of s for a derivative; a sum whose automatic split fails continues.

Calibrated: without the early failure, a 3D sum at the split 0.03 takes 29 s to fail at the shell limit.