Extract lambda to a named function to ensure cache hits.

The lambda function used in `jax.pmap` within `_test_slice_execution` is moved into a private helper function `_plus_one`. lambda functions have a different hash and were not utilizing the compilation cache.

https://docs.jax.dev/en/latest/jit-compilation.html#jit-and-caching

FUTURE_COPYBARA_INTEGRATE_REVIEW=#122 from AI-Hypercomputer:prepare_for_version 53e7715
PiperOrigin-RevId: 833936348

Author: lukebaumann

pathwaysutils/elastic/manager.py

@@ -44,6 +44,20 @@
 _logger = logging.getLogger(__name__)
 
 
+def _plus_one(x: jax.Array) -> jax.Array:
+  """Adds one to each element in the array.
+
+  Used to test if a slice is available.
+
+  Args:
+    x: The array to add one to.
+
+  Returns:
+      The array with one added to each element.
+  """
+  return x + 1
+
+
 class ElasticRuntimeError(RuntimeError):
   """Error raised when elasticity cannot continue.
 
@@ -234,7 +248,7 @@ def _simple_execution(self, devices: Sequence[jax.Device]) -> jax.Array:
         self._SIMPLE_EXECUTION_TEST_VALUE - 1
     )
 
-    return jax.pmap(lambda x: x + 1, devices=devices)(test_input)
+    return jax.pmap(_plus_one, devices=devices)(test_input)
 
   @timing.timeit
   def get_slice_availability(self) -> set[int]: