Specialize matmul to batched dot

Author: ricardoV94

pytensor/tensor/rewriting/blas.py

@@ -59,6 +59,8 @@
 
 import numpy as np
 
+from pytensor.tensor.rewriting.basic import register_specialize
+
 
 try:
     import numpy.__config__  # noqa
@@ -79,12 +81,12 @@
 )
 from pytensor.graph.rewriting.db import SequenceDB
 from pytensor.graph.utils import InconsistencyError
-from pytensor.printing import debugprint
 from pytensor.tensor import basic as at
 from pytensor.tensor.blas import (
     Dot22,
     _dot22,
     _dot22scalar,
+    batched_dot,
     gemm_inplace,
     gemm_no_inplace,
     gemv_inplace,
@@ -94,7 +96,7 @@
 )
 from pytensor.tensor.elemwise import DimShuffle, Elemwise
 from pytensor.tensor.exceptions import NotScalarConstantError
-from pytensor.tensor.math import Dot, add, mul, neg, sub
+from pytensor.tensor.math import Dot, _matrix_matrix_matmul, add, mul, neg, sub
 from pytensor.tensor.rewriting.elemwise import local_dimshuffle_lift
 from pytensor.tensor.type import (
     DenseTensorType,
@@ -899,9 +901,32 @@ def local_dot22_to_dot22scalar(fgraph, node):
 )
 
 
-# from opt import register_specialize, register_canonicalize
-# @register_specialize
-@node_rewriter([sub, add])
-def local_print_as_we_go_along(fgraph, node):
-    if node.op in (sub, add):
-        debugprint(node)
+@register_specialize
+@node_rewriter([_matrix_matrix_matmul])
+def specialize_matmul_to_batched_dot(fgraph, node):
+    """Rewrite Matmul (Blockwise matrix-matrix) without implicit broadcasted batched dimension as BatchedDot.
+
+    TODO: Do the same for Blockwise BatchedDot
+    """
+    x, y = node.inputs
+
+    # BatchedDot does not allow implicit broadcasting of the batch dimensions
+    # We do not want to explicitly broadcast as it may result in huge arrays
+    if x.type.broadcastable[:-2] != y.type.broadcastable[:-2]:
+        return None
+
+    x_shape = tuple(x.shape)
+    y_shape = tuple(y.shape)
+    if len(x_shape) > 3:
+        # If we have more than one batch dim, ravel it
+        x = x.reshape((-1, x_shape[-2], x_shape[-1]))
+        y = y.reshape((-1, y_shape[-2], y_shape[-1]))
+
+    new_out = batched_dot(x, y)
+
+    if len(x_shape) > 3:
+        # And then unravel it
+        new_out = new_out.reshape((*x_shape[:-2], x_shape[-2], y_shape[-1]))
+
+    copy_stack_trace(node.outputs, [new_out])
+    return [new_out]

tests/tensor/rewriting/test_blas.py

@@ -0,0 +1,48 @@
+import numpy as np
+import pytest
+
+from pytensor import function
+from pytensor.compile import get_default_mode
+from pytensor.tensor import matmul, tensor, vectorize
+from pytensor.tensor.blas import BatchedDot
+from pytensor.tensor.blockwise import Blockwise
+from pytensor.tensor.rewriting.blas import specialize_matmul_to_batched_dot
+
+
+@pytest.mark.parametrize("valid_case", (True, False))
+def test_specialize_matmul_to_batched_dot(valid_case):
+    signature = BatchedDot.gufunc_signature
+    rewrite = specialize_matmul_to_batched_dot.__name__
+
+    def core_pt(x, y):
+        return matmul(x, y)
+
+    def core_np(x, y):
+        return np.matmul(x, y)
+
+    x = tensor(shape=(7, 5, 3, 3))
+    if valid_case:
+        y = tensor(shape=(7, 5, 3, 3))
+    else:
+        y = tensor(shape=(5, 3, 3))
+
+    vectorize_pt = function(
+        [x, y],
+        vectorize(core_pt, signature=signature)(x, y),
+        mode=get_default_mode().including(rewrite),
+    )
+    blocwkise_node = any(
+        isinstance(node.op, Blockwise) for node in vectorize_pt.maker.fgraph.apply_nodes
+    )
+    if valid_case:
+        assert not blocwkise_node
+    else:
+        assert blocwkise_node
+
+    x_test = np.random.normal(size=x.type.shape).astype(x.type.dtype)
+    y_test = np.random.normal(size=y.type.shape).astype(y.type.dtype)
+    vectorize_np = np.vectorize(core_np, signature=signature)
+    np.testing.assert_allclose(
+        vectorize_pt(x_test, y_test),
+        vectorize_np(x_test, y_test),
+    )

tests/tensor/test_blockwise.py

@@ -6,13 +6,15 @@
 
 import pytensor
 from pytensor import config, function
+from pytensor.compile import get_mode
 from pytensor.gradient import grad
 from pytensor.graph import Apply, Op
 from pytensor.graph.replace import vectorize_node
 from pytensor.raise_op import assert_op
 from pytensor.tensor import diagonal, log, tensor
 from pytensor.tensor.blockwise import Blockwise
 from pytensor.tensor.nlinalg import MatrixInverse
+from pytensor.tensor.rewriting.blas import specialize_matmul_to_batched_dot
 from pytensor.tensor.slinalg import Cholesky, Solve, cholesky, solve_triangular
 from pytensor.tensor.utils import _parse_gufunc_signature
 
@@ -45,7 +47,11 @@ def check_blockwise_runtime_broadcasting(mode):
     b = tensor("b", shape=(None, 5, 3))
 
     out = a @ b
-    fn = function([a, b], out, mode=mode)
+    fn = function(
+        [a, b],
+        out,
+        mode=get_mode(mode).excluding(specialize_matmul_to_batched_dot.__name__),
+    )
     assert isinstance(fn.maker.fgraph.outputs[0].owner.op, Blockwise)
 
     for valid_test_values in [