Merge pull request #3858 from jobh/numpy-array-elements-without-map

Use non-mapped strategies for populating numpy arrays

hypothesis-python/RELEASE.rst

@@ -0,0 +1,4 @@
+RELEASE_TYPE: patch
+
+Improves the performance of the :func:`~hypothesis.extra.numpy.arrays`
+strategy when generating unique values.

hypothesis-python/src/hypothesis/extra/numpy.py

@@ -46,8 +46,14 @@
 from hypothesis.internal.coverage import check_function
 from hypothesis.internal.reflection import proxies
 from hypothesis.internal.validation import check_type
+from hypothesis.strategies._internal.lazy import unwrap_strategies
 from hypothesis.strategies._internal.numbers import Real
-from hypothesis.strategies._internal.strategies import Ex, T, check_strategy
+from hypothesis.strategies._internal.strategies import (
+    Ex,
+    MappedSearchStrategy,
+    T,
+    check_strategy,
+)
 from hypothesis.strategies._internal.utils import defines_strategy
 
 
@@ -393,7 +399,6 @@ def do_draw(self, data):
         return result
 
 
-@check_function
 def fill_for(elements, unique, fill, name=""):
     if fill is None:
         if unique or not elements.has_reusable_values:
@@ -508,6 +513,11 @@ def arrays(
             )
         elements = from_dtype(dtype, **(elements or {}))
     check_strategy(elements, "elements")
+    # If there's a redundant cast to the requested dtype, remove it.  This unlocks
+    # optimizations such as fast unique sampled_from, and saves some time directly too.
+    unwrapped = unwrap_strategies(elements)
+    if isinstance(unwrapped, MappedSearchStrategy) and unwrapped.pack == dtype.type:
+        elements = unwrapped.mapped_strategy
     if isinstance(shape, int):
         shape = (shape,)
     shape = tuple(shape)