Table 1. Feature overview for different trust-region optimization implementations.

The non least-squares column indicates whether the method is applicable to non least-squares problems. The free column indicates whether the implementation is freely available or proprietary software.

Optimizer	Subspace	Non least-squares	BFGS/SR1	Programming Language	free
lsqnonlin	${\mathcal{S}}_{2\mathrm{D}}$	□	□	MATLAB	□
fmincon	${\mathcal{S}}_{2\mathrm{D}}$	✓	□	MATLAB	□
ls_trf	${\mathbb{R}}^{n_{\theta }}$ , ${\mathcal{S}}_{2\mathrm{D}}$	□	□	Python	✓
fides	${\mathbb{R}}^{n_{\theta }}$ , ${\mathcal{S}}_{2\mathrm{D}}$	✓	✓	Python	✓