DOC Clarify GaussianProcessRegressor default kernel behavior
@@ -45,8 +45,10 @@ class GaussianProcessRegressor(MultiOutputMixin,
----------
kernel : kernel instance, default=None
The kernel specifying the covariance function of the GP. If None is
- passed, the kernel "1.0 * RBF(1.0)" is used as default. Note that
- the kernel's hyperparameters are optimized during fitting.
+ passed, the kernel ``ConstantKernel(1.0, constant_value_bounds="fixed"
+ * RBF(1.0, length_scale_bounds="fixed")`` is used as default. Note that
+ the kernel hyperparameters are optimized during fitting unless the
+ bounds are marked as "fixed".
alpha : float or ndarray of shape (n_samples,), default=1e-10
Value added to the diagonal of the kernel matrix during fitting.
