Function calculate_lebail_pattern 

pub fn calculate_lebail_pattern(
    pattern: &PatternRecord,
    instrument: ConstantWavelengthInstrument,
    phases: &[LeBailPhase],
    support_fwhm: f64,
    execution: &ExecutionPolicy,
) -> Result<LeBailCalculation, LeBailError>

Calculate all fixed phases through one native fused accumulation.

Errors

Returns LeBailError for invalid pattern/profile state or allocation.