when restoring the sampler, try to update the queue_size of the sampler

when using the pool

Author: segasai

CHANGELOG.md

@@ -7,6 +7,7 @@ The format is based on [Keep a Changelog](https://keepachangelog.com/en/1.0.0/),
 [Unreleased]
 ### Added
 ### Changed
+- When restoring the sampler with the pool, try to use an updated value of queue_size based on pool size
 ### Fixed
 
 [3.0.0 - 2025-10-04]

py/dynesty/dynesty.py

@@ -18,7 +18,8 @@
 from .bounding import BOUND_LIST
 from . import bounding
 from .dynamicsampler import DynamicSampler
-from .utils import (LogLikelihood, get_random_generator, get_nonbounded)
+from .utils import (LogLikelihood, get_random_generator, get_nonbounded,
+                    _parse_pool_queue)
 
 __all__ = ["NestedSampler", "DynamicNestedSampler", "_function_wrapper"]
 
@@ -199,32 +200,6 @@ def _get_enlarge_bootstrap(sample, enlarge, bootstrap):
                              'sense unless bootstrap=0 or enlarge = 1')
 
 
-def _parse_pool_queue(pool, queue_size):
-    """
-    Common functionality of interpretign the pool and queue_size
-    arguments to Dynamic and static nested samplers
-    """
-    if queue_size is not None and queue_size < 1:
-        raise ValueError("The queue must contain at least one element!")
-    elif (queue_size == 1) or (pool is None and queue_size is None):
-        mapper = map
-        queue_size = 1
-    elif pool is not None:
-        mapper = pool.map
-        if queue_size is None:
-            try:
-                queue_size = pool.size
-            except AttributeError as e:
-                raise ValueError("Cannot initialize `queue_size` because "
-                                 "`pool.size` has not been provided. Please"
-                                 "define `pool.size` or specify `queue_size` "
-                                 "explicitly.") from e
-    else:
-        raise ValueError("`queue_size > 1` but no `pool` provided.")
-
-    return mapper, queue_size
-
-
 def _check_first_update(first_update):
     """
     Verify that the first_update dictionary is valid

py/dynesty/utils.py

@@ -2147,7 +2147,18 @@ def restore_sampler(fname, pool=None):
             f'does not match the current dynesty version'
             f'({DYNESTY_VERSION}). That is *NOT* guaranteed to work')
     if pool is not None:
-        mapper = pool.map
+        queue_size_old = getattr(sampler, 'queue_size')
+        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
     if hasattr(sampler, 'sampler'):
@@ -2206,3 +2217,28 @@ def save_sampler(sampler, fname):
         except:  # noqa
             pass
         raise
+
+
+def _parse_pool_queue(pool, queue_size):
+    """
+    Common functionality of interpreting the pool and queue_size
+    arguments to Dynamic and static nested samplers
+    """
+    if queue_size is not None and queue_size < 1:
+        raise ValueError("The queue must contain at least one element!")
+    if pool is None:
+        if queue_size > 1:
+            raise ValueError("`queue_size > 1` but no `pool` provided.")
+        mapper = map
+        queue_size = 1
+    elif pool is not None:
+        mapper = pool.map
+        if queue_size is None:
+            queue_size = getattr(pool, '_processes') or getattr(pool, 'size')
+            if queue_size is None:
+                raise ValueError(
+                    "Cannot initialize `queue_size` because "
+                    "`pool.size` or pool._processes has not been provided. "
+                    "Please `define `pool.size` or specify `queue_size` "
+                    "explicitly.")
+    return mapper, queue_size