add n_draws and t_sampling report to smc (#3931)

* add n_draws and t_sampling report to smc

* add _n_tune

* update release notes

* resolve conflicts

Author: aloctavodia

Diff for: RELEASE-NOTES.md

@@ -17,6 +17,7 @@
 - `pm.Data` container can now be used for index variables, i.e with integer data and not only floats (issue [#3813](https://github.com/pymc-devs/pymc3/issues/3813), fixed by [#3925](https://github.com/pymc-devs/pymc3/pull/3925)).
 - `pm.Data` container can now be used as input for other random variables (issue [#3842](https://github.com/pymc-devs/pymc3/issues/3842), fixed by [#3925](https://github.com/pymc-devs/pymc3/pull/3925)).
 - Plots and Stats API sections now link to ArviZ documentation [#3927](https://github.com/pymc-devs/pymc3/pull/3927)
+- Add `SamplerReport` with properties `n_draws`, `t_sampling` and `n_tune` to SMC. `n_tune` is always 0 [#3931](https://github.com/pymc-devs/pymc3/issues/3931).
 
 ### Maintenance
 - Tuning results no longer leak into sequentially sampled `Metropolis` chains (see #3733 and #3796).

Diff for: pymc3/smc/sample_smc.py

@@ -12,8 +12,9 @@
 #   See the License for the specific language governing permissions and
 #   limitations under the License.
 
-from .smc import SMC
+import time
 import logging
+from .smc import SMC
 
 
 def sample_smc(
@@ -144,6 +145,7 @@ def sample_smc(
         random_seed=random_seed,
     )
 
+    t1 = time.time()
     _log = logging.getLogger("pymc3")
     _log.info("Sample initial stage: ...")
     stage = 0
@@ -170,5 +172,7 @@ def sample_smc(
         smc.pool.join()
 
     trace = smc.posterior_to_trace()
-
+    trace.report._n_draws = smc.draws
+    trace.report._n_tune = 0
+    trace.report._t_sampling = time.time() - t1
     return trace