Design 2->4

src/array_api_extra/_lib/_funcs.py

@@ -544,6 +544,7 @@ def setdiff1d(
     /,
     *,
     assume_unique: bool = False,
+    size: int | None = None,
     fill_value: object | None = None,
     xp: ModuleType | None = None,
 ) -> Array:
@@ -561,11 +562,16 @@ def setdiff1d(
     assume_unique : bool
         If ``True``, the input arrays are both assumed to be unique, which
         can speed up the calculation. Default is ``False``.
-    fill_value : object, optional
-        Pad the output array with this value.
+    size : int, optional
+        The size of the output array. This is exclusively used inside the JAX JIT, and
+        only for as long as JAX does not support arrays of unknown size inside it. In
+        all other cases, it is disregarded.
+        Returned elements will be clipped if they are more than size, and padded with
+        `fill_value` if they are less. Default: raise if inside ``jax.jit``.
 
-        This is exclusively used for JAX arrays when running inside ``jax.jit``,
-        where all array shapes need to be known in advance.
+    fill_value : object, optional
+        Pad the output array with this value. This is exclusively used for JAX arrays
+        when running inside ``jax.jit``. Default: 0.
     xp : array_namespace, optional
         The standard-compatible namespace for `x1` and `x2`. Default: infer.
 
@@ -630,7 +636,7 @@ def _dask_impl(x1: Array, x2: Array) -> Array:  # numpydoc ignore=PR01,RT01
         return x1 if assume_unique else xp.unique_values(x1)
 
     def _jax_jit_impl(
-        x1: Array, x2: Array, fill_value: object | None
+        x1: Array, x2: Array, size: int | None, fill_value: object | None
     ) -> Array:  # numpydoc ignore=PR01,RT01
         """
         JAX implementation inside jax.jit.
@@ -639,9 +645,9 @@ def _jax_jit_impl(
         and not being able to filter by a boolean mask.
         Returns array the same size as x1, padded with fill_value.
         """
-        # unique_values inside jax.jit is not supported unless it's got a fixed size
-        mask = _x1_not_in_x2(x1, x2)
-
+        if size is None:
+            msg = "`size` is mandatory when running inside `jax.jit`."
+            raise ValueError(msg)
         if fill_value is None:
             fill_value = xp.zeros((), dtype=x1.dtype)
         else:
@@ -650,9 +656,13 @@ def _jax_jit_impl(
                 msg = "`fill_value` must be a scalar."
                 raise ValueError(msg)
 
+        # unique_values inside jax.jit is not supported unless it's got a fixed size
+        mask = _x1_not_in_x2(x1, x2)
         x1 = xp.where(mask, x1, fill_value)
-        # Note: jnp.unique_values sorts
-        return xp.unique_values(x1, size=x1.size, fill_value=fill_value)
+        # Move fill_value to the right
+        x1 = xp.take(x1, xp.argsort(~mask, stable=True))
+        x1 = x1[:size]
+        x1 = xp.unique_values(x1, size=size, fill_value=fill_value)
 
     if is_dask_namespace(xp):
         return _dask_impl(x1, x2)
@@ -666,7 +676,7 @@ def _jax_jit_impl(
             jax.errors.ConcretizationTypeError,
             jax.errors.NonConcreteBooleanIndexError,
         ):
-            return _jax_jit_impl(x1, x2, fill_value)  # inside jax.jit
+            return _jax_jit_impl(x1, x2, size, fill_value)  # inside jax.jit
 
     return _generic_impl(x1, x2)