# GaussianProcess

`class boulderopal.closed_loop.GaussianProcess(bounds, length_scale_bounds=None, seed=None)`

The Gaussian process optimizer.

### Parameters

**bounds**(*Bounds*) – The bounds on the test points.**length_scale_bounds**(*np.ndarray**or**None**,**optional*) – The per-parameter length scale bounds on the test points. The bounds must be a NumPy array of shape`(parameter_count, 2)`

where the trailing axis are the bounds for each parameter (with the lower bound first, followed by the upper bound). If not specified,`optimize`

will pick a value derived from the bounds by picking orders of magnitudes below/above the sidelength for each box axis.**seed**(*int**or**None**,**optional*) – Seed for the random number generator used in the optimizer. If set, must be a non-negative integer. Use this option to generate deterministic results from the optimizer.

## Notes

The Gaussian process is defined by the kernel

$k({\mathbf x}_j, {\mathbf x}_k) = \exp \left(-\frac{1}{2} ( {\mathbf x}_j - {\mathbf x}_k )^\top \Sigma^{-2} ( {\mathbf x}_j - {\mathbf x}_k )\right) ,$where ${\mathbf x}_j$ is an $n$-dimensional vector representing the $j$-th test point, $\Sigma= {\rm diag}(l_1, \cdots, l_n)$ is an $n \times n$ diagonal matrix, and $\{ l_j \}$ are the length scales. The length scales are tuned while training the model, within the bounds set by the length_scale_bounds parameter. Roughly speaking, the amount a parameter needs to change to impact the optimization cost should lie within the length scale bounds.

It’s recommended to provide non-zero cost_uncertainty to `optimize`

when using this optimizer, otherwise you might encounter a numerical error when the optimizer
tries to fit the kernel with your input data. If the error persists, try increasing the
cost_uncertainty value or decreasing the minimum length scale bound. However, such numerical
error is also an indication that your data might not be suitable to be modelled by a
Gaussian process, and in that case, consider using a different closed-loop optimizer.

For more detail on Gaussian processes see Gaussian process on Wikipedia.