perf(mge/functional): reduce matmul python overhead

GitOrigin-RevId: 738d0da10ee7efdf3bd3e3030f10ac9c8aa16a5c

imperative/python/megengine/core/tensor/tensor_wrapper.py

@@ -345,9 +345,10 @@ class ArrayMethodMixin(abc.ABC):
     @property
     def ndim(self):
         shape = self.shape
-        # XXX: assume ndim is not changed during trace
         if isinstance(shape, self.__class__):
-            shape = shape.numpy()
+            # XXX: assume ndim is not changed during trace
+            ndim = shape.__wrapped__.shape[0]
+            return ndim
         return len(shape)
 
     @property

imperative/python/megengine/functional/nn.py

@@ -10,6 +10,7 @@
 from typing import Optional, Sequence, Tuple, Union
 
 from ..core._imperative_rt import CompNode
+from ..core._trace_option import use_symbolic_shape
 from ..core.ops import builtin
 from ..core.ops._internal import param_defs as P
 from ..core.ops.builtin import BatchNorm
@@ -1015,23 +1016,39 @@ def matmul(
         remove_col = True
 
     batch_shape = None
-    shape1 = astensor1d(inp1.shape, inp1, dtype="int32", device=inp1.device)
-    shape2 = astensor1d(inp2.shape, inp2, dtype="int32", device=inp2.device)
+    shape1 = inp1.shape
+    shape2 = inp2.shape
+
+    maxdim = dim1 if dim1 > dim2 else dim2
     if dim1 >= 3 or dim2 >= 3:
-        if dim1 == dim2:
-            assert (
-                shape1[:-2] == shape2[:-2]
-            ).min(), "operands could not be broadcasted together."
-        if dim1 > dim2:
-            shape2 = concat([shape1[:-2], shape2[-2:]])
-            inp2 = broadcast_to(inp2, shape2)
-        if dim1 < dim2:
-            shape1 = concat([shape2[:-2], shape1[-2:]])
-            inp1 = broadcast_to(inp1, shape1)
-        batch_shape = shape1[:-2]
-        # compress inputs to 3d
-        inp1 = inp1.reshape(concat([prod(shape1[:-2]), shape1[-2:]]))
-        inp2 = inp2.reshape(concat([prod(shape2[:-2]), shape2[-2:]]))
+        if use_symbolic_shape():
+            if dim1 > dim2:
+                shape2 = concat([shape1[:-2], shape2[-2:]])
+                inp2 = broadcast_to(inp2, shape2)
+            if dim1 < dim2:
+                shape1 = concat([shape2[:-2], shape1[-2:]])
+                inp1 = broadcast_to(inp1, shape1)
+            if maxdim > 3:
+                batch_shape = shape1[:-2]
+                # compress inputs to 3d
+                (inp1,) = apply(
+                    builtin.Reshape(), inp1, concat([prod(shape1[:-2]), shape1[-2:]])
+                )
+                (inp2,) = apply(
+                    builtin.Reshape(), inp2, concat([prod(shape2[:-2]), shape2[-2:]])
+                )
+        else:
+            if dim1 > dim2:
+                shape2 = shape1[:-2] + shape2[-2:]
+                inp2 = broadcast_to(inp2, shape2)
+            if dim1 < dim2:
+                shape1 = shape2[:-2] + shape1[-2:]
+                inp1 = broadcast_to(inp1, shape1)
+            if maxdim > 3:
+                batch_shape = shape1[:-2]
+                # compress inputs to 3d
+                inp1 = inp1.reshape((-1, shape1[-2], shape1[-1]))
+                inp2 = inp2.reshape((-1, shape2[-2], shape2[-1]))
 
         op = builtin.BatchedMatrixMul(
             transposeA=transpose_a,
@@ -1048,8 +1065,13 @@ def matmul(
         )
 
     (result,) = apply(op, inp1, inp2)
-    if batch_shape is not None:
-        result = result.reshape(concat([batch_shape, result.shape[-2:]]))
+    if maxdim > 3:
+        if use_symbolic_shape():
+            (result,) = apply(
+                builtin.Reshape(), result, concat([batch_shape, result.shape[-2:]])
+            )
+        else:
+            result = result.reshape(batch_shape + result.shape[-2:])
     if remove_row:
         result = squeeze(result, axis=-2)
     if remove_col: