with respect to 𝜽 where 𝜽 is taken as the starting point of the minimization (see Figure ). We must stress that 𝜸 (log 𝝉 , 𝜽) in must be discretized at the same collocation points as 𝜸 (log 𝝉 , 𝜆 ). Nonetheless, the log-timescale vectors log 𝝉 in and in are not necessarily identical since a denser grid for 𝜸 (log 𝝉 , 𝜽) can be used during training (see Section 2.5.3 for more details).