Support Blockwise in JAX backend

Author: ricardoV94

pytensor/link/jax/dispatch/__init__.py

@@ -13,5 +13,6 @@
 import pytensor.link.jax.dispatch.elemwise
 import pytensor.link.jax.dispatch.scan
 import pytensor.link.jax.dispatch.sparse
+import pytensor.link.jax.dispatch.blockwise
 
 # isort: on

pytensor/link/jax/dispatch/blockwise.py

@@ -0,0 +1,29 @@
+import jax.numpy as jnp
+
+from pytensor.graph import FunctionGraph
+from pytensor.link.jax.dispatch import jax_funcify
+from pytensor.tensor.blockwise import Blockwise
+
+
+@jax_funcify.register(Blockwise)
+def funcify_Blockwise(op: Blockwise, node, *args, **kwargs):
+    signature = op.signature
+    core_node = op._create_dummy_core_node(node.inputs)
+    core_fgraph = FunctionGraph(inputs=core_node.inputs, outputs=core_node.outputs)
+    tuple_core_fn = jax_funcify(core_fgraph)
+
+    if len(node.outputs) == 1:
+
+        def core_fn(*inputs):
+            return tuple_core_fn(*inputs)[0]
+
+    else:
+        core_fn = tuple_core_fn
+
+    vect_fn = jnp.vectorize(core_fn, signature=signature)
+
+    def blockwise_fn(*inputs):
+        op._check_runtime_broadcast(node, inputs)
+        return vect_fn(*inputs)
+
+    return blockwise_fn

tests/link/jax/test_blockwise.py

@@ -0,0 +1,42 @@
+import numpy as np
+import pytest
+
+from pytensor import config
+from pytensor.graph import FunctionGraph
+from pytensor.tensor import tensor
+from pytensor.tensor.blockwise import Blockwise
+from pytensor.tensor.math import Dot, matmul
+from tests.link.jax.test_basic import compare_jax_and_py
+from tests.tensor.test_blockwise import check_blockwise_runtime_broadcasting
+
+
+jax = pytest.importorskip("jax")
+
+
+def test_runtime_broadcasting():
+    check_blockwise_runtime_broadcasting("JAX")
+
+
+# Equivalent blockwise to matmul but with dumb signature
+odd_matmul = Blockwise(Dot(), signature="(i00,i01),(i10,i11)->(o00,o01)")
+
+
+@pytest.mark.parametrize("matmul_op", (matmul, odd_matmul))
+def test_matmul(matmul_op):
+    rng = np.random.default_rng(14)
+    a = tensor("a", shape=(2, 3, 5))
+    b = tensor("b", shape=(2, 5, 3))
+    test_values = [
+        rng.normal(size=(inp.type.shape)).astype(config.floatX) for inp in (a, b)
+    ]
+
+    out = matmul_op(a, b)
+    assert isinstance(out.owner.op, Blockwise)
+    fg = FunctionGraph([a, b], [out])
+    fn, _ = compare_jax_and_py(fg, test_values)
+
+    # Check we are not adding any unnecessary stuff
+    jaxpr = str(jax.make_jaxpr(fn.vm.jit_fn)(*test_values))
+    jaxpr = jaxpr.replace("name=jax_funcified_fgraph", "name=matmul")
+    expected_jaxpr = str(jax.make_jaxpr(jax.jit(jax.numpy.matmul))(*test_values))
+    assert jaxpr == expected_jaxpr