Added simple workarounds for gather_mm and segment_mm (#57)

* Added simple workarounds for gather_mm and segment_mm. See #56

* bumping python and pytorch version in CI

* enabling black on notebooks in CI

* updating github actions to avoid deprecation warning

Author: tvercaut

.github/workflows/black.yml

@@ -6,5 +6,7 @@ jobs:
   lint:
     runs-on: ubuntu-latest
     steps:
-      - uses: actions/checkout@v3
+      - uses: actions/checkout@v4
       - uses: psf/black@stable
+        with:
+          jupyter: true

.github/workflows/python-package.yml

@@ -12,21 +12,28 @@ jobs:
     strategy:
       fail-fast: false
       matrix:
-        python-version: ["3.8", "3.9", "3.10"]
-        torch-version: ["1.13.1", "2.0.1"]
+        python-version: ["3.8", "3.10", "3.12"]
+        torch-version: ["1.13.1", "2.4.1"]
+        exclude:
+        - python-version: "3.12"
+          torch-version: "1.13.1"
 
     steps:
-    - uses: actions/checkout@v3
+    - uses: actions/checkout@v4
     - name: Set up Python ${{ matrix.python-version }}
-      uses: actions/setup-python@v3
+      uses: actions/setup-python@v5
       with:
         python-version: ${{ matrix.python-version }}
     - name: Install dependencies
       run: |
         python -m pip install --upgrade pip
         pip install torch==${{ matrix.torch-version }}
-        python -m pip install flake8 black
+        python -m pip install flake8 black[jupyter]
         if [ -f requirements-dev.txt ]; then pip install -r requirements-dev.txt; fi
+    - name: numpy downgrade for pytorch 1.x
+      if: startsWith(matrix.torch-version, '1.')
+      run: |
+        pip install "numpy<2"
     - name: Lint check with flake8
       run: |
         # stop the build if there are Python syntax errors or undefined names

setup.py

@@ -18,8 +18,9 @@ def readme():
         "Programming Language :: Python :: 3.8",
         "Programming Language :: Python :: 3.9",
         "Programming Language :: Python :: 3.10",
+        "Programming Language :: Python :: 3.12",
     ],
-    python_requires=">=3.8, <3.11",
+    python_requires=">=3.8",
     keywords="sparse torch utility",
     url="https://github.com/cai4cai/torchsparsegradutils",
     author="CAI4CAI research group",

torchsparsegradutils/__init__.py

@@ -1,5 +1,13 @@
 from .sparse_matmul import sparse_mm
+from .indexed_matmul import gather_mm, segment_mm
 from .sparse_solve import sparse_triangular_solve, sparse_generic_solve
 from .sparse_lstsq import sparse_generic_lstsq
 
-__all__ = ["sparse_mm", "sparse_triangular_solve", "sparse_generic_solve", "sparse_generic_lstsq"]
+__all__ = [
+    "sparse_mm",
+    "gather_mm",
+    "segment_mm",
+    "sparse_triangular_solve",
+    "sparse_generic_solve",
+    "sparse_generic_lstsq",
+]

torchsparsegradutils/indexed_matmul.py

@@ -0,0 +1,117 @@
+import torch
+
+try:
+    import dgl.ops as dglops
+
+    dgl_installed = True
+except ImportError:
+    dgl_installed = False
+
+
+def segment_mm(a, b, seglen_a):
+    """
+    Performs matrix multiplication according to segments.
+    See https://docs.dgl.ai/generated/dgl.ops.segment_mm.html
+
+    Suppose ``seglen_a == [10, 5, 0, 3]``, the operator will perform
+    four matrix multiplications::
+
+        a[0:10] @ b[0], a[10:15] @ b[1],
+        a[15:15] @ b[2], a[15:18] @ b[3]
+
+    Args:
+        a (torch.Tensor): The left operand, 2-D tensor of shape ``(N, D1)``
+        b (torch.Tensor): The right operand, 3-D tensor of shape ``(R, D1, D2)``
+        seglen_a (torch.Tensor): An integer tensor of shape ``(R,)``. Each element is the length of segments of input ``a``. The summation of all elements must be equal to ``N``.
+
+    Returns:
+        torch.Tensor: The output dense matrix of shape ``(N, D2)``
+    """
+    if torch.__version__ < (2, 4):
+        raise NotImplementedError("PyTorch version is too old for nested tesors")
+
+    if dgl_installed:
+        # DGL is probably more computationally efficient
+        # See https://github.com/pytorch/pytorch/issues/136747
+        return dglops.segment_mm(a, b, seglen_a)
+
+    if not a.dim() == 2 or not b.dim() == 3 or not seglen_a.dim() == 1:
+        raise ValueError("Input tensors have unexpected dimensions")
+
+    N, _ = a.shape
+    R, D1, D2 = b.shape
+
+    # Sanity check sizes
+    if not a.shape[1] == D1 or not seglen_a.shape[0] == R:
+        raise ValueError("Incompatible size for inputs")
+
+    segidx_a = torch.cumsum(seglen_a[:-1], dim=0)
+
+    # Ideally the conversions below to nested tensor would be handled natively
+    nested_a = torch.nested.as_nested_tensor(torch.tensor_split(a, segidx_a, dim=0))
+    nested_b = torch.nested.as_nested_tensor(list(map(torch.squeeze, torch.split(b, 1, dim=0))))
+
+    # The actual gather matmul computation
+    nested_ab = torch.matmul(nested_a, nested_b)
+
+    # Convert back to tensors, again ideally this would be handled natively
+    ab = torch.cat(nested_ab.unbind(), dim=0)
+    return ab
+
+
+def gather_mm(a, b, idx_b):
+    """
+    Gather data according to the given indices and perform matrix multiplication.
+    See https://docs.dgl.ai/generated/dgl.ops.gather_mm.html
+
+    Let the result tensor be ``c``, the operator conducts the following computation:
+
+      c[i] = a[i] @ b[idx_b[i]]
+      , where len(c) == len(idx_b)
+
+    Args:
+        a (torch.Tensor): A 2-D tensor of shape ``(N, D1)``
+        b (torch.Tensor): A 3-D tensor of shape ``(R, D1, D2)``
+        idx_b (torch.Tensor): An 1-D integer tensor of shape ``(N,)``.
+
+    Returns:
+        torch.Tensor: The output dense matrix of shape ``(N, D2)``
+    """
+    if torch.__version__ < (2, 4):
+        raise NotImplementedError("PyTorch version is too old for nested tesors")
+
+    if dgl_installed:
+        # DGL is more computationally efficient
+        # See https://github.com/pytorch/pytorch/issues/136747
+        return dglops.gather_mm(a, b, idx_b)
+
+    # Dependency free fallback
+    if not isinstance(a, torch.Tensor) or not isinstance(b, torch.Tensor) or not isinstance(idx_b, torch.Tensor):
+        raise ValueError("Inputs should be instances of torch.Tensor")
+
+    if not a.dim() == 2 or not b.dim() == 3 or not idx_b.dim() == 1:
+        raise ValueError("Input tensors have unexpected dimensions")
+
+    N = idx_b.shape[0]
+    R, D1, D2 = b.shape
+
+    # Sanity check sizes
+    if not a.shape[0] == N or not a.shape[1] == D1:
+        raise ValueError("Incompatible size for inputs")
+
+    torchdevice = a.device
+    src_idx = torch.arange(N, device=torchdevice)
+
+    # Ideally the conversions below to nested tensor would be handled without for looops and without copy
+    nested_a = torch.nested.as_nested_tensor([a[idx_b == i, :] for i in range(R)])
+    src_idx_reshuffled = torch.cat([src_idx[idx_b == i] for i in range(R)])
+    nested_b = torch.nested.as_nested_tensor([b[i, :, :].squeeze() for i in range(R)])
+
+    # The actual gather matmul computation
+    nested_ab = torch.matmul(nested_a, nested_b)
+
+    # Convert back to tensors, again, ideally this would be handled natively with no copy
+    ab_segmented = torch.cat(nested_ab.unbind(), dim=0)
+    ab = torch.empty((N, D2), device=torchdevice)
+    ab[src_idx_reshuffled] = ab_segmented
+    return ab

torchsparsegradutils/tests/test_indexed_matmul.py

@@ -0,0 +1,94 @@
+import torch
+import pytest
+
+if torch.__version__ < (2, 4):
+    pytest.skip(
+        "Skipping test based on nested tensors since an old version of pytorch is used", allow_module_level=True
+    )
+
+from torchsparsegradutils import gather_mm, segment_mm
+
+# Identify Testing Parameters
+DEVICES = [torch.device("cpu")]
+if torch.cuda.is_available():
+    DEVICES.append(torch.device("cuda"))
+
+TEST_DATA = [
+    # name  N, R, D1, D2
+    ("small", 100, 32, 7, 10),
+]
+
+INDEX_DTYPES = [torch.int32, torch.int64]
+VALUE_DTYPES = [torch.float32, torch.float64]
+
+ATOL = 1e-6  # relaxed tolerance to allow for float32
+RTOL = 1e-4
+
+
+# Define Test Names:
+def data_id(shapes):
+    return shapes[0]
+
+
+def device_id(device):
+    return str(device)
+
+
+def dtype_id(dtype):
+    return str(dtype).split(".")[-1]
+
+
+# Define Fixtures
+
+
+@pytest.fixture(params=TEST_DATA, ids=[data_id(d) for d in TEST_DATA])
+def shapes(request):
+    return request.param
+
+
+@pytest.fixture(params=VALUE_DTYPES, ids=[dtype_id(d) for d in VALUE_DTYPES])
+def value_dtype(request):
+    return request.param
+
+
+@pytest.fixture(params=INDEX_DTYPES, ids=[dtype_id(d) for d in INDEX_DTYPES])
+def index_dtype(request):
+    return request.param
+
+
+@pytest.fixture(params=DEVICES, ids=[device_id(d) for d in DEVICES])
+def device(request):
+    return request.param
+
+
+# Define Tests
+
+
+def test_segment_mm(device, value_dtype, index_dtype, shapes):
+    _, N, R, D1, D2 = shapes
+
+    a = torch.randn((N, D1), device=device)
+    b = torch.randn((R, D1, D2), device=device)
+    seglen_a = torch.randint(low=1, high=int(N / R), size=(R,), device=device)
+    seglen_a[-1] = N - seglen_a[:-1].sum()
+
+    ab = segment_mm(a, b, seglen_a)
+
+    k = 0
+    for i in range(R):
+        for j in range(seglen_a[i]):
+            assert torch.allclose(ab[k, :].squeeze(), a[k, :].squeeze() @ b[i, :, :].squeeze(), atol=ATOL, rtol=RTOL)
+            k += 1
+
+
+def test_gather_mm(device, value_dtype, index_dtype, shapes):
+    _, N, R, D1, D2 = shapes
+
+    a = torch.randn((N, D1), device=device)
+    b = torch.randn((R, D1, D2), device=device)
+    idx_b = torch.randint(low=0, high=R, size=(N,), device=device)
+
+    ab = gather_mm(a, b, idx_b)
+
+    for i in range(N):
+        assert torch.allclose(ab[i, :].squeeze(), a[i, :].squeeze() @ b[idx_b[i], :, :].squeeze(), atol=ATOL, rtol=RTOL)