I am getting and Eigen error when trying to provide initial chain values when using a simplex parameter:

`ERRORAssertion failed: (index >= 0 && index < size()), function operator[], file stan/lib/stan_math/lib/eigen_3.3.3/Eigen/src/Core/DenseCoeffsBase.h, line 408.`

Runs without the `inits`

argument seem to start without issues, not using the simplex variable and providing `inits`

also seems to start the chain. I am using CmdStanPy. Thanks.

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This implies that you are trying to acces elements wiht index out of bounds. Too many init values maybe?

I got that much from googling the error for Eigen, but the simplex documentation is not clear on that. Should the `inits`

for a simplex of size `K`

have `K-1`

elements?

`K`

elements. But I’m afraid the problem is this bug which makes `inits`

not work for some constrained types.

3 Likes

I see, it’s not something that can be fixed in the Stan code, then, I presume. Thanks.