Currently the algebraic solver requires that the vector of input parameters `theta`

is larger than zero, but this makes it awkward when trying to use the algebraic solver in the `transformed data`

block where the gradients aren’t needed. Technically in this case there’s an ambiguity between whether external parameters are placed into `theta`

or `x_r`

and placing them all in `theta`

does work, it’s just not as natural as placing them in `x_r`

.

@charlesm93, any reason why the algebraic solver shouldn’t proceed to solve the system without any gradients when `theta`

is a zero-length vector?