added docs

README.md

@@ -13,14 +13,18 @@
 
 --------------------------------------------------------------------------------
 
-This package consists of a small extension library of optimized sparse matrix operations for the use in [PyTorch](http://pytorch.org/), which are missing and or lack autograd support in the main package.
+[PyTorch](http://pytorch.org/) (<= 0.4.1) completely lacks autograd support and operations such as sparse sparse matrix multiplication, but is heavily working on improvement (*cf.* [this issue](https://github.com/pytorch/pytorch/issues/9674)).
+In the meantime, this package consists of a small extension library of optimized sparse matrix operations with autograd support.
 This package currently consists of the following methods:
 
-* **[Autograd Sparse Tensor Creation](#autograd-sparse-tensor-creation)**
-* **[Autograd Sparse Tensor Value Extraction](#autograd-sparse-tensor-value-extraction)**
+* **[Coalesce](#coalesce)**
+* **[Transpose](#transpose)**
+* **[Sparse Dense Matrix Multiplication](#sparse-dense-matrix-multiplication)**
 * **[Sparse Sparse Matrix Multiplication](#sparse-sparse-matrix-multiplication)**
 
 All included operations work on varying data types and are implemented both for CPU and GPU.
+To avoid the hazzle of creating [`torch.sparse_coo_tensor`](https://pytorch.org/docs/stable/torch.html?highlight=sparse_coo_tensor#torch.sparse_coo_tensor), this package defines operations on sparse tensors by simply passing `index` and `value` tensors as arguments ([with same shapes as defined in PyTorch](https://pytorch.org/docs/stable/sparse.html)).
+Note that only `value` comes with autograd support, as `index` is discrete and therefore not differentiable.
 
 ## Installation
 
@@ -45,60 +49,176 @@ pip install torch-scatter torch-sparse
 
 If you are running into any installation problems, please create an [issue](https://github.com/rusty1s/pytorch_sparse/issues).
 
-## Autograd Sparse Tensor Creation
+## Coalesce
 
 ```
-torch_sparse.sparse_coo_tensor(torch.LongTensor, torch.Tensor, torch.Size) -> torch.SparseTensor
+torch_sparse.coalesce(index, value, m, n, op="add", fill_value=0) -> (torch.LongTensor, torch.Tensor)
 ```
 
-Constructs a [`torch.SparseTensor`](https://pytorch.org/docs/stable/sparse.html) with autograd capabilities w.r.t. `value`.
+Row-wise sorts `value` and removes duplicate entries.
+Duplicate entries are removed by scattering them together.
+For scattering, any operation of [`torch_scatter`](https://github.com/rusty1s/pytorch_scatter) can be used.
+
+### Parameters
+
+* **index** *(LongTensor)* - The index tensor of sparse matrix.
+* **value** *(Tensor)* - The value tensor of sparse matrix.
+* **m** *(int)* - First dimension of sparse matrix.
+* **n** *(int)* - Second dimension of sparse matrix.
+* **op** *(string, optional)* - Scatter operation to use. (default: `"add"`)
+* **fill_value** *(int, optional)* - Initial fill value of scatter operation. (default: `0`)
+
+### Returns
+
+* **index** *(LongTensor)* - Coalesced index tensor of sparse matrix.
+* **value** *(Tensor)* - Coalesced value tensor of sparse matrix.
+
+### Example
 
 ```python
-from torch_sparse import sparse_coo_tensor
+from torch_sparse import coalesce
+
+index = torch.tensor([[1, 0, 1, 0, 2, 1],
+                      [0, 1, 1, 1, 0, 0]])
+value = torch.tensor([[1, 2], [2, 3], [3, 4], [4, 5], [5, 6], [6, 7]])
 
-i = torch.tensor([[0, 1, 1],
-                  [2, 0, 2]])
-v = torch.Tensor([3, 4, 5], requires_grad=True)
-A = sparse_coo_tensor(i, v, torch.Size([2,3]))
+index, value = coalesce(index, value, m=3, n=2)
 ```
 
-This method may become obsolete in future PyTorch releases (>= 0.4.1) as reported by this [issue](https://github.com/pytorch/pytorch/issues/9674).
+```
+print(index)
+tensor([[0, 1, 1, 2],
+        [1, 0, 1, 0]])
+print(value)
+tensor([[6, 8], [7, 9], [3, 4], [5, 6]])
+```
 
-## Autograd Sparse Tensor Value Extraction
+## Transpose
 
 ```
-torch_sparse.to_value(torch.SparseTensor) -> torch.Tensor
+torch_sparse.transpose(index, value, m, n) -> (torch.LongTensor, torch.Tensor)
 ```
 
-Wrapper method to support autograd on values of [`torch.SparseTensor`](https://pytorch.org/docs/stable/sparse.html).
+Transposes dimensions 0 and 1 of a sparse matrix.
+
+### Parameters
+
+* **index** *(LongTensor)* - The index tensor of sparse matrix.
+* **value** *(Tensor)* - The value tensor of sparse matrix.
+* **m** *(int)* - First dimension of sparse matrix.
+* **n** *(int)* - Second dimension of sparse matrix.
+
+### Returns
+
+* **index** *(LongTensor)* - Transposed index tensor of sparse matrix.
+* **value** *(Tensor)* - Transposed value tensor of sparse matrix.
+
+### Example
 
 ```python
-from torch_sparse import to_value
+from torch_sparse import transpose
+
+index = torch.tensor([[1, 0, 1, 0, 2, 1],
+                      [0, 1, 1, 1, 0, 0]])
+value = torch.tensor([[1, 2], [2, 3], [3, 4], [4, 5], [5, 6], [6, 7]])
 
-i = torch.tensor([[0, 1, 1],
-                  [2, 0, 2]])
-v = torch.Tensor([3, 4, 5], requires_grad=True)
-A = torch.sparse_coo_tensor(i, v, torch.Size([2,3]), requires_grad=True)
-v = to_value(A)
+index, value = transpose(index, value, m=3, n=2)
 ```
 
-This method may become obsolete in future PyTorch releases (>= 0.4.1) as reported by this [issue](https://github.com/pytorch/pytorch/issues/9674).
+```
+print(index)
+tensor([[0, 0, 1, 1],
+        [1, 2, 0, 1]])
+print(value)
+tensor([[7, 9],
+        [5, 6],
+        [6, 8],
+        [3, 4]])
+```
 
-## Sparse Sparse Matrix Multiplication
+## Sparse Dense Matrix Multiplication
 
 ```
-torch_sparse.spspmm(torch.SparseTensor, torch.SparseTensor) -> torch.SparseTensor
+torch_sparse.spmm(index, value, m, matrix) -> torch.Tensor
 ```
 
-Sparse matrix product of two sparse tensors with autograd support.
+Matrix product of a sparse matrix with a dense matrix.
+
+### Parameters
 
+* **index** *(LongTensor)* - The index tensor of sparse matrix.
+* **value** *(Tensor)* - The value tensor of sparse matrix.
+* **m** *(int)* - First dimension of sparse matrix.
+* **matrix** *(int)* - Dense matrix.
+
+### Returns
+
+* **out** *(Tensor)* - Dense output matrix.
+
+### Example
+
+```python
+from torch_sparse import spmm
+
+index = torch.tensor([[0, 0, 1, 2, 2],
+                      [0, 2, 1, 0, 1]])
+value = torch.tensor([1, 2, 4, 1, 3])
+matrix = torch.tensor([[1, 4], [2, 5], [3, 6]])
+
+out = spmm(index, value, 3, matrix)
+```
+
+```
+print(out)
+tensor([[7, 16],
+        [8, 20],
+        [7, 19]])
 ```
+
+## Sparse Sparse Matrix Multiplication
+
+```
+torch_sparse.spspmm(indexA, valueA, indexB, valueB, m, k, n) -> (torch.LongTensor, torch.Tensor)
+```
+
+Matrix product of two sparse tensors.
+Both input sparse matrices need to be **coalesced**.
+
+### Parameters
+
+* **indexA** *(LongTensor)* - The index tensor of first sparse matrix.
+* **valueA** *(Tensor)* - The value tensor of first sparse matrix.
+* **indexB** *(LongTensor)* - The index tensor of second sparse matrix.
+* **valueB** *(Tensor)* - The value tensor of second sparse matrix.
+* **m** *(int)* - First dimension of first sparse matrix.
+* **k** *(int)* - Second dimension of first sparse matrix and first dimension of second sparse matrix.
+* **n** *(int)* - Second dimension of second sparse matrix.
+
+### Returns
+
+* **index** *(LongTensor)* - Output index tensor of sparse matrix.
+* **value** *(Tensor)* - Output value tensor of sparse matrix.
+
+### Example
+
+```python
 from torch_sparse import spspmm
 
-A = torch.sparse_coo_tensor(..., requries_grad=True)
-B = torch.sparse_coo_tensor(..., requries_grad=True)
+indexA = torch.tensor([[0, 0, 1, 2, 2], [1, 2, 0, 0, 1]])
+valueA = torch.tensor([1, 2, 3, 4, 5])
+
+indexB = torch.tensor([[0, 2], [1, 0]])
+valueB = torch.tensor([2, 4])
 
-C = spspmm(A, B)
+indexC, valueC = spspmm(indexA, valueA, indexB, valueB, 3, 3, 2)
+```
+
+```
+print(index)
+tensor([[0, 1, 2],
+        [0, 1, 1]])
+print(value)
+tensor([8, 6, 8])
 ```
 
 ## Running tests

torch_sparse/coalesce.py

@@ -3,7 +3,7 @@ import torch_scatter
 
 
 def coalesce(index, value, m, n, op='add', fill_value=0):
-    """Row-wise reorders and removes duplicate entries in sparse matrixx."""
+    """Row-wise reorders and removes duplicate entries in sparse matrix."""
 
     row, col = index
 
@@ -16,5 +16,7 @@ def coalesce(index, value, m, n, op='add', fill_value=0):
     if value is not None:
         op = getattr(torch_scatter, 'scatter_{}'.format(op))
         value = op(value, inv, 0, None, perm.size(0), fill_value)
+        if isinstance(value, tuple):
+            value = value[0]
 
     return index, value