@@ -261,40 +261,6 @@ with (3) a large number of varying live points can make the stopping criteria
261261difficult to evaluate quickly. See
262262:ref: `Nested Sampling Errors ` for additional details.
263263
264- **I'm trying to sample using gradients but getting extremely poor performance.
265- I thought gradients were supposed to make sampling more efficient!
266- What gives? **
267-
268- While gradients are extremely useful in terms of substantially improving
269- the scaling of most sampling methods with dimensionality (gradient-based
270- methods have better polynomial scaling than non-gradient slice sampling, both
271- of which are *substantially * better over the runaway exponential scaling
272- of random walks), it can take a while for these benefits to really kick in.
273- These scaling arguments generally ignore the constant prefactor, which
274- can be quite large for many gradient-based approaches that require
275- integrating along some trajectory, often resulting in (at least) dozens of
276- function calls per sample. This often makes it more efficient to run simpler
277- sampling techniques on lower-dimensional problems. In general, Nested Sampling
278- methods are also unable to exploit gradient-based information to the same
279- degree as Hamiltonian Monte Carlo approaches, which further degrades
280- performance and scaling relative to what you might naively expect.
281-
282- If you feel like your performance is poorer than expected even given these
283- caveats, or if you notice other results that make you highly suspicious of the
284- resulting samples, please double-check the :ref: `Sampling with Gradients `
285- page to make sure you've passed in the correct log-likelihood gradient and are
286- dealing with the unit cube Jacobian properly. Failing
287- to apply this (or applying it twice) violates conservation of energy and
288- momentum and leads to the integration timesteps along the trajectories
289- changing in undesirable ways.
290- It's also possible the numerical errors in the Jacobian (if you've set
291- `compute_jac=True `) might be propagating through to the computed trajectories.
292- If so, consider trying to compute the analytic Jacobian by hand to reduce
293- the impact of numerical errors.
294-
295- If you still find subpar performance, please feel free to
296- `open an issue <https://github.com/joshspeagle/dynesty/issues >`_.
297-
298264
299265Live Point Questions
300266--------------------
0 commit comments