update queue_size restoration

Author: segasai

docs/source/quickstart.rst

@@ -655,7 +655,7 @@ If you used the pool in the sampler and you want to use the pool after restoring
     sampler.run_nested(resume=True)
 
 You should be careful when restoring the sampler on machine with different number of CPUs when using a pool.
-We will try to update the queue_size based on what is the pool size.
+We will still use the original queue_size unless it was 1 before.
 
 The checkpointing may be helpful if you are running dynesty on HPC with a queue system that has a limit on a wall-time that your jobs can run.
 There is a however an important reminder that should *NOT* use checkpointing for persistence. I.e. if you want to save the results of the sampling, you should save samples, weights or the results object, rather than the whole nested sampling object (as checkpointing does). The reason for this is that the checkpoint files are not guaranteed to be compatible between dynesty versions (even minor ones).

py/dynesty/utils.py

@@ -2146,21 +2146,21 @@ def restore_sampler(fname, pool=None):
             f'The dynesty version in the checkpoint file ({save_ver})'
             f'does not match the current dynesty version'
             f'({DYNESTY_VERSION}). That is *NOT* guaranteed to work')
-    if pool is not None:
-        queue_size_old = getattr(sampler, 'queue_size', None)
-        try:
-            # we first try to get the new queue_size
-            # that may fail if the pool has no information about the size
-            mapper, queue_size_new = _parse_pool_queue(pool, None)
-        except ValueError:
-            # if first failed we are using the new queue_size
-            mapper, queue_size_new = _parse_pool_queue(pool, queue_size_old)
-
-        if queue_size_new is not None and queue_size_new > queue_size_old:
-            warnings.warn(
-                f'Restoring the sampler with queue_size {queue_size_old}')
-    else:
-        mapper = map
+
+    queue_size_old = getattr(sampler, 'queue_size', None)
+    try:
+        # we first try to get the new queue_size
+        # that may fail if the pool has no information about the size
+        mapper, queue_size_new = _parse_pool_queue(pool, None)
+    except ValueError:
+        # if first failed we are using the old queue_size
+        mapper, queue_size_new = _parse_pool_queue(pool, queue_size_old)
+
+    if queue_size_new != queue_size_old and queue_size_old != 1:
+        warnings.warn(
+            f'Restoring the sampler with queue_size {queue_size_old}')
+        queue_size_new = queue_size_old
+
     if hasattr(sampler, 'sampler'):
         # This is the case of the dynamic sampler
         # this is better be written as isinstanceof()
@@ -2179,6 +2179,7 @@ def restore_sampler(fname, pool=None):
     for cursamp in samplers:
         cursamp.mapper = mapper
         cursamp.pool = pool
+        cursamp.queue_size = queue_size_new
     return sampler