[MRG] Replaced coo_matrix with coo_array better compatability and added tes… (#782)

* Replaced coo_matrix with coo_array better compatability and added test to test coo_array functionnality

* Updated release file

* Replaced some more coo_matrix calls

---------

Co-authored-by: Rémi Flamary <remi.flamary@gmail.com>

Author: nathanneike

RELEASES.md

@@ -6,6 +6,7 @@ This new release adds support for sparse cost matrices in the exact EMD solver.
 
 #### New features
 - Add support for sparse cost matrices in exact EMD solver `ot.emd` and `ot.emd2` (PR #778)
+- Migrate backend from deprecated `scipy.sparse.coo_matrix` to modern `scipy.sparse.coo_array` API (PR #TBD)
 
 #### Closed issues
 - Add support for sparse cost matrices in EMD solver (PR #778, Issue #397)

ot/backend.py

@@ -94,7 +94,7 @@
 import scipy
 import scipy.linalg
 import scipy.special as special
-from scipy.sparse import coo_matrix, csr_matrix, issparse
+from scipy.sparse import coo_array, csr_matrix, issparse
 
 DISABLE_TORCH_KEY = "POT_BACKEND_DISABLE_PYTORCH"
 DISABLE_JAX_KEY = "POT_BACKEND_DISABLE_JAX"
@@ -802,9 +802,9 @@ def coo_matrix(self, data, rows, cols, shape=None, type_as=None):
         r"""
         Creates a sparse tensor in COOrdinate format.
 
-        This function follows the api from :any:`scipy.sparse.coo_matrix`
+        This function follows the api from :any:`scipy.sparse.coo_array`
 
-        See: https://docs.scipy.org/doc/scipy/reference/generated/scipy.sparse.coo_matrix.html
+        See: https://docs.scipy.org/doc/scipy/reference/generated/scipy.sparse.coo_array.html
         """
         raise NotImplementedError()
 
@@ -1354,9 +1354,9 @@ def randperm(self, size, type_as=None):
 
     def coo_matrix(self, data, rows, cols, shape=None, type_as=None):
         if type_as is None:
-            return coo_matrix((data, (rows, cols)), shape=shape)
+            return coo_array((data, (rows, cols)), shape=shape)
         else:
-            return coo_matrix((data, (rows, cols)), shape=shape, dtype=type_as.dtype)
+            return coo_array((data, (rows, cols)), shape=shape, dtype=type_as.dtype)
 
     def issparse(self, a):
         return issparse(a)
@@ -1384,9 +1384,9 @@ def todense(self, a):
             return a
 
     def sparse_coo_data(self, a):
-        # Convert to COO format if needed
-        if not isinstance(a, coo_matrix):
-            a_coo = coo_matrix(a)
+        # Convert to COO array format if needed
+        if not isinstance(a, coo_array):
+            a_coo = coo_array(a)
         else:
             a_coo = a
 
@@ -1815,9 +1815,7 @@ def sparse_coo_data(self, a):
         # JAX doesn't support sparse matrices, so this shouldn't be called
         # But if it is, convert the dense array to sparse using scipy
         a_np = self.to_numpy(a)
-        from scipy.sparse import coo_matrix
-
-        a_coo = coo_matrix(a_np)
+        a_coo = coo_array(a_np)
         return a_coo.row, a_coo.col, a_coo.data, a_coo.shape
 
     def where(self, condition, x=None, y=None):
@@ -2804,10 +2802,10 @@ def coo_matrix(self, data, rows, cols, shape=None, type_as=None):
         rows = self.from_numpy(rows)
         cols = self.from_numpy(cols)
         if type_as is None:
-            return cupyx.scipy.sparse.coo_matrix((data, (rows, cols)), shape=shape)
+            return cupyx.scipy.sparse.coo_array((data, (rows, cols)), shape=shape)
         else:
             with cp.cuda.Device(type_as.device):
-                return cupyx.scipy.sparse.coo_matrix(
+                return cupyx.scipy.sparse.coo_array(
                     (data, (rows, cols)), shape=shape, dtype=type_as.dtype
                 )
 

ot/plot.py

@@ -15,6 +15,8 @@
 import numpy as np
 import matplotlib.pylab as pl
 from matplotlib import gridspec
+from . import backend
+from scipy.sparse import issparse, coo_array
 
 
 def plot1D_mat(
@@ -232,8 +234,6 @@ def plot2D_samples_mat(xs, xt, G, thr=1e-8, **kwargs):
         parameters given to the plot functions (default color is black if
         nothing given)
     """
-    from . import backend
-    from scipy.sparse import issparse, coo_matrix
 
     if ("color" not in kwargs) and ("c" not in kwargs):
         kwargs["color"] = "k"
@@ -258,7 +258,7 @@ def plot2D_samples_mat(xs, xt, G, thr=1e-8, **kwargs):
         # Not a backend array, check if scipy.sparse
         is_sparse = issparse(G)
         if is_sparse:
-            G_coo = G if isinstance(G, coo_matrix) else G.tocoo()
+            G_coo = G if isinstance(G, coo_array) else G.tocoo()
             rows, cols, data = G_coo.row, G_coo.col, G_coo.data
 
     if is_sparse:

test/test_ot.py

@@ -992,6 +992,15 @@ def test_emd_sparse_vs_dense(nx):
         b, nx.to_numpy(nx.sum(G_sparse_dense, 0)), rtol=1e-5, atol=1e-7
     )
 
+    # Test coo_array element-wise multiplication (only works with coo_array, not coo_matrix)
+    if nx.__name__ == "numpy":
+        # This tests that we're using coo_array which supports element-wise operations
+        M_sparse_np = M_sparse
+        G_sparse_np = G_sparse
+        loss_sparse = np.sum(G_sparse_np * M_sparse_np)
+        # Verify the loss calculation is reasonable
+        assert loss_sparse >= 0, "Sparse loss should be non-negative"
+
 
 def test_emd2_sparse_vs_dense(nx):
     """Test that sparse and dense emd2 solvers produce identical costs.