[torch-mlir][sparse] replace ad-hoc mechanism with proper FX export (llvm#3648)

Now that the PyDev feature request pytorch/pytorch#117188 has been
completed, we can remove all the ad-hoc code that propagates sparsity
metadata and replace it with the built-int PyDev metadata for sparse
tensors. This removes a lot of code and also ensures sparsity is
consistent with the torch.sparse package for all cases.

Author: aartbik

python/torch_mlir/extras/fx_importer.py

@@ -369,63 +369,47 @@ def sympy_expr_to_semi_affine_expr(
         )
 
 
-@dataclass(frozen=True)
-class SparsityMeta:
-    """
-    Class for keeping track of sparsity meta data.
-
-    NOTE: this will be fully replaced by
-          torch.fx.passes.shape_prop.SparseTensorMetadata
-    """
-
-    layout: torch.layout
-    batch_dim: int
-    sparse_dim: int
-    dense_dim: int
-    blocksize: Optional[Tuple[int, int]]
-    pos_dtype: torch.dtype
-    crd_dtype: torch.dtype
-
-
-def sparsity_encoding(shape: torch.Size, sparsity: SparsityMeta) -> str:
-    """Returns sparse tensor encoding for the given sparse layout as string."""
-    assert sparsity is not None
+def sparsity_encoding(t: torch.Tensor) -> str:
+    """Returns sparse tensor encoding for the given tensor as string."""
 
     # Sparse tensors have the form
     #   [ <batch_dimensions> , <sparse_dimensions>, <dense_dimensions> ]
     # which map directly to MLIR types.
-    batch_dim, sparse_dim, dense_dim = (
-        sparsity.batch_dim,
-        sparsity.sparse_dim,
-        sparsity.dense_dim,
+    dim, batch_dim, sparse_dim, dense_dim = (
+        t.ndim,
+        t.ndim - t.sparse_dim() - t.dense_dim(),
+        t.sparse_dim(),
+        t.dense_dim(),
     )
-    dim = batch_dim + sparse_dim + dense_dim
-    assert dim == len(shape)
-    blocksize = sparsity.blocksize
-
     dims = ",".join(f"d{d}" for d in range(dim))
 
-    if sparsity.layout is torch.sparse_coo:
-        assert sparse_dim >= 2 and blocksize is None
+    if t.layout is torch.sparse_coo:
+        assert sparse_dim >= 2
         trail_dim = batch_dim + sparse_dim - 1
         coords = ",".join(
             f"d{d}:singleton(nonunique,soa)" for d in range(batch_dim + 1, trail_dim)
         )
         sep = "," if sparse_dim > 2 else ""
         lvls = f"d{batch_dim}:compressed(nonunique),{coords}{sep}d{trail_dim}:singleton(soa)"
-    elif sparsity.layout is torch.sparse_csr:
-        assert sparse_dim == 2 and blocksize is None
+        idx_dtype = t._indices().dtype  # supports uncoalesced COO tensors
+    elif t.layout is torch.sparse_csr:
+        assert sparse_dim == 2
         lvls = f"d{batch_dim}:dense,d{batch_dim+1}:compressed"
-    elif sparsity.layout is torch.sparse_csc:
-        assert sparse_dim == 2 and blocksize is None
+        idx_dtype = t.col_indices().dtype
+    elif t.layout is torch.sparse_csc:
+        assert sparse_dim == 2
         lvls = f"d{batch_dim+1}:dense,d{batch_dim}:compressed"
+        idx_dtype = t.row_indices().dtype
     else:
-        assert sparse_dim == 2 and blocksize is not None
-        if sparsity.layout is torch.sparse_bsr:
+        assert sparse_dim == 2
+        blocksize = t.values().shape[batch_dim + 1 : batch_dim + 3]
+        if t.layout is torch.sparse_bsr:
             i, j = batch_dim, batch_dim + 1
+            idx_dtype = t.col_indices().dtype
         else:
-            assert sparsity.layout is torch.sparse_bsc
+            assert t.layout is torch.sparse_bsc
             j, i = batch_dim, batch_dim + 1
+            idx_dtype = t.row_indices().dtype
         m, n = blocksize
         lvls = (
             f"d{i} floordiv {m}:dense,d{j} floordiv {n}:compressed,"
@@ -440,8 +424,7 @@ def sparsity_encoding(shape: torch.Size, sparsity: SparsityMeta) -> str:
         dense = ",".join(f"d{d}:dense" for d in range(batch_dim + sparse_dim, dim))
         lvls = f"{lvls},{dense}"
 
-    posw = torch.iinfo(sparsity.pos_dtype).bits
-    crdw = torch.iinfo(sparsity.crd_dtype).bits
+    posw = crdw = torch.iinfo(idx_dtype).bits
     return f"#sparse_tensor.encoding<{{map=({dims})->({lvls}),posWidth={posw},crdWidth={crdw}}}>"
 
 
@@ -1043,20 +1026,27 @@ def get_vtensor_type(
         shape: torch.Size,
         dtype: torch.dtype,
         *,
-        sparsity: Optional[SparsityMeta] = None,
+        val: Optional[torch.Tensor] = None,
         mutable: bool = False,
     ):
         """Return IrType for !torch.vtensor with the given shape and dtype"""
         stem = "torch.tensor" if mutable else "torch.vtensor"
         shape_asm = self.format_asm_shape(shape)
         mlir_dtype = str(self.dtype_to_type(dtype))
-        if sparsity is not None:
-            encoding = sparsity_encoding(shape, sparsity)
-            assert encoding is not None
+        if val is not None and val.layout in [
+            torch.sparse_coo,
+            torch.sparse_csr,
+            torch.sparse_csc,
+            torch.sparse_bsr,
+            torch.sparse_bsc,
+        ]:
+            # This is a sparse tensor.
+            encoding = sparsity_encoding(val)
             return IrType.parse(
                 f"!{stem}<[{shape_asm}],{str(mlir_dtype)},{encoding}>",
                 context=self._c,
             )
+        # This is a dense tensor.
         return IrType.parse(
             f"!{stem}<[{shape_asm}],{str(mlir_dtype)}>", context=self._c
         )
@@ -1065,21 +1055,17 @@ def node_val_to_type(self, node: torch_fx.Node, *, mutable: bool = False) -> IrT
         try:
             tensor_meta = node.meta.get("tensor_meta")
             val = node.meta.get("val")
-            sparsity = node.meta.get("sparsity", None)
         except KeyError as e:
             raise RuntimeError(
                 f"FIXME: Illegal access to torch.fx.Node.meta: {e} ({node.meta.keys()} : {node.meta})"
             )
-        return self.value_info_to_type(
-            val, tensor_meta=tensor_meta, sparsity=sparsity, mutable=mutable
-        )
+        return self.value_info_to_type(val, tensor_meta=tensor_meta, mutable=mutable)
 
     def value_info_to_type(
         self,
         val,
         *,
         tensor_meta: Optional[TensorMetadata] = None,
-        sparsity=None,
         mutable: bool = False,
     ):
         if tensor_meta is not None:
@@ -1097,14 +1083,14 @@ def value_info_to_type(
                 )
             else:
                 return self.tensor_metadata_to_type(
-                    tensor_meta, sparsity=sparsity, mutable=mutable
+                    tensor_meta, val=val, mutable=mutable
                 )
         elif val is not None:
             # some nodes with symbolic inputs pass a 'val' attribute rather than
             # tensor_meta
             if isinstance(val, TorchFakeTensor):
                 return self.get_vtensor_type(
-                    val.size(), val.dtype, sparsity=sparsity, mutable=mutable
+                    val.size(), val.dtype, val=val, mutable=mutable
                 )
             elif isinstance(val, list) and all(
                 isinstance(x, TorchFakeTensor) for x in val
@@ -1126,19 +1112,17 @@ def tensor_metadata_to_type(
         self,
         tm: TensorMetadata,
         *,
-        sparsity: Optional[SparsityMeta] = None,
+        val: Optional[torch.Tensor] = None,
         mutable: bool = False,
     ) -> IrType:
         tm_shape = tuple(
             item.node if is_symbolic(item) else item for item in list(tm.shape)
         )
 
-        key = (tm_shape, tm.dtype, sparsity, mutable)
+        key = (tm_shape, tm.dtype, val, mutable)
         t = self._tensor_metadata_cache.get(key)
         if t is None:
-            t = self.get_vtensor_type(
-                tm.shape, tm.dtype, sparsity=sparsity, mutable=mutable
-            )
+            t = self.get_vtensor_type(tm.shape, tm.dtype, val=val, mutable=mutable)
             self._tensor_metadata_cache[key] = t
         return t
 

test/python/fx_importer/sparsity/lit.local.cfg

@@ -0,0 +1,10 @@
+config.unsupported = True
+
+try:
+  import torch
+  if "2.5.0" <= str(torch.__version__):
+    print("Enabling sparsity propagation tests")
+    config.unsupported = False
+
+except ModuleNotFoundError:
+  ...

test/python/fx_importer/sparse_test.py test/python/fx_importer/sparsity/sparse_test.py

@@ -8,13 +8,11 @@
 from typing import Any, Callable, Optional, Tuple, Dict
 
 import torch
-import torch.export
 import torch.nn as nn
 import numpy as np
 
 from torch_mlir.extras.fx_decomp_util import get_decomposition_table
 from torch_mlir.extras.fx_importer import FxImporter
-from torch_mlir.extras.fx_importer import SparsityMeta
 from torch_mlir import ir
 from torch_mlir.dialects import torch as torch_d
 from torch_mlir.compiler_utils import run_pipeline_with_repro_report
@@ -23,139 +21,15 @@
 )
 
 
-# All sparse layouts currently supported in torch.sparse.
-SPARSE_LAYOUTS = [
-    torch.sparse_coo,
-    torch.sparse_csr,
-    torch.sparse_csc,
-    torch.sparse_bsr,
-    torch.sparse_bsc,
-]
-
-
-def sparse_metadata(a: torch.Tensor) -> SparsityMeta:
-    """
-    Returns a meta data tuple for the given sparse tensor.
-
-    NOTE: this will be fully replaced by fx graph SparseTensorMetadata
-    """
-    sparse_dim = a.sparse_dim()
-    dense_dim = a.dense_dim()
-    batch_dim = a.ndim - dense_dim - sparse_dim
-    blocksize = None
-    if a.layout is torch.sparse_coo:
-        return SparsityMeta(
-            a.layout,
-            batch_dim,
-            sparse_dim,
-            dense_dim,
-            blocksize,
-            a._indices().dtype,
-            a._indices().dtype,
-        )
-    elif a.layout is torch.sparse_csr or a.layout is torch.sparse_bsr:
-        if a.layout is torch.sparse_bsr:
-            blocksize = a.values().shape[batch_dim + 1 : batch_dim + 3]
-        return SparsityMeta(
-            a.layout,
-            batch_dim,
-            sparse_dim,
-            dense_dim,
-            blocksize,
-            a.crow_indices().dtype,
-            a.col_indices().dtype,
-        )
-    elif a.layout is torch.sparse_csc or a.layout is torch.sparse_bsc:
-        if a.layout is torch.sparse_bsc:
-            blocksize = a.values().shape[batch_dim + 1 : batch_dim + 3]
-        return SparsityMeta(
-            a.layout,
-            batch_dim,
-            sparse_dim,
-            dense_dim,
-            blocksize,
-            a.ccol_indices().dtype,
-            a.row_indices().dtype,
-        )
-    else:
-        raise RuntimeError(f"Unsupported sparse layout for {a}")
-
-
-def sparse_export(
-    f: Callable, args: Tuple[Any, ...], kwargs: Optional[Dict[str, Any]] = None
-) -> torch.export.ExportedProgram:
-    """
-    This is a ***temporary*** wrapper around `torch.export.export`
-    that eventually should be removed and simply replaced by the
-    standard API for exporting traced graphs.
-
-    But until issue
-
-      https://github.com/pytorch/pytorch/pull/117907
-
-    is addressed, this wrapper provides support for the sparse
-    tensor types by first converting all operands to dense tensors,
-    building the traced graph as for the dense case, then annotating
-    sparse parameters with their actual sparse layout attributes,
-    followed by some simple propagation rules. This temporary solution
-    accelerates testing torch-mlir with PyTorch sparse tensors until
-    the issue is resolved upstream.
-    """
-    # Convert all arguments to dense.
-    dargs = tuple(a.to_dense() if a.layout in SPARSE_LAYOUTS else a for a in args)
-    mask = [a.layout in SPARSE_LAYOUTS for a in args]
-    # Build the regular FX traced graph with only dense arguments
-    # (the current version would crash otherwise, see issue above).
-    prog = torch.export.export(f, dargs, kwargs)
-    decomposition_table = get_decomposition_table()
-    if decomposition_table:
-        prog = prog.run_decompositions(decomposition_table)
-    # Annotate sparse arguments in the graph and apply some very
-    # basic propagation rules for sparsity.
-    specs = prog.graph_signature.input_specs
-    alen = len(specs)
-    k = 0
-    for i, node in enumerate(prog.graph.nodes):
-        if node.op == "placeholder":
-            # Argument.
-            spec = specs[i]
-            if spec.kind is torch.export.graph_signature.InputKind.USER_INPUT:
-                if mask[k]:
-                    node.meta["sparsity"] = sparse_metadata(args[k])
-                k = k + 1
-        elif node.op == "call_function":
-            opname = node.target._schema.name.split("::")[1]
-            # Zero preserving elt-wise unary op.
-            if opname in {"abs", "neg", "relu", "sin"}:
-                node.meta["sparsity"] = node.args[0].meta.get("sparsity", None)
-            elif opname == "_to_sparse" or opname == "to_sparse":
-                dim = len(node.meta.get("val").shape)
-                node.meta["sparsity"] = SparsityMeta(
-                    torch.sparse_coo, 0, dim, 0, None, torch.int64, torch.int64
-                )
-            # TODO: Uncomment this to hack sparsity into the network.
-            # elif opname == "_to_dense" or opname == "to_dense":
-            #     # hack (assumes we never really want the to_dense for now)
-            #     node.meta["sparsity"] = node.args[0].meta.get("sparsity", None)
-            elif opname == "select" and node.args[0].meta.get("sparsity", None):
-                dim = len(node.meta.get("val").shape)
-                node.meta["sparsity"] = SparsityMeta(
-                    torch.sparse_coo, 0, dim, 0, None, torch.int64, torch.int64
-                )
-            elif opname == "stack" and node.args[0][0].meta.get("sparsity", None):
-                dim = len(node.meta.get("val").shape)
-                node.meta["sparsity"] = SparsityMeta(
-                    torch.sparse_coo, 0, dim - 1, 1, None, torch.int64, torch.int64
-                )
-    return prog
-
-
 def export_and_import(f, *args, **kwargs):
-    """This method implements Stella's importer, stripped down to essentials."""
+    """A FX graph importer, stripped down to essentials."""
     context = ir.Context()
     torch_d.register_dialect(context)
     fx_importer = FxImporter(context=context)
-    prog = sparse_export(f, args, kwargs)
+    prog = torch.export.export(f, args, kwargs)
+    decomposition_table = get_decomposition_table()
+    if decomposition_table:
+        prog = prog.run_decompositions(decomposition_table)
     fx_importer.import_frozen_program(prog)
     return fx_importer.module
 
@@ -175,8 +49,7 @@ def sparse_jit(f, *args, **kwargs):
         enable_ir_printing=False,
     )
     # Compile with reference Linalg backend.
-    # TODO: runtime verification currently fails with 'rank mismatch' on
-    # memref.cast. Need to fix the IR first.
+    # TODO: runtime verification ails with 'rank mismatch' on memref.cast
     backend = RefBackendLinalgOnTensorsBackend(generate_runtime_verification=False)
     compiled = backend.compile(module)
     invoker = backend.load(compiled)
@@ -218,7 +91,8 @@ def sparse_jit(f, *args, **kwargs):
 
 
 def run(f):
-    print(f"{f.__name__}")
+    # Prompt test name and torch version (for debugging).
+    print(f"{f.__name__} ({torch.__version__})")
     print("-" * len(f.__name__))
     f()
     print()