[MRG] add kl_loss to all semi-relaxed (f)gw solvers

RELEASES.md

@@ -14,6 +14,7 @@
 + Upgraded unbalanced OT solvers for more flexibility (PR #539)
 + Add LazyTensor for modeling plans and low rank tensor in large scale OT (PR #544)
 + Add exact line-search for `gromov_wasserstein` and `fused_gromov_wasserstein` with KL loss (PR #556)
++ Add KL loss to all semi-relaxed (Fused) Gromov-Wasserstein solvers (PR #559)
 
 #### Closed issues
 - Fix line search evaluating cost outside of the interpolation range (Issue #502, PR #504)

ot/gromov/_semirelaxed.py

@@ -56,7 +56,6 @@ def semirelaxed_gromov_wasserstein(C1, C2, p=None, loss_fun='square_loss', symme
         If let to its default value None, uniform distribution is taken.
     loss_fun : str
         loss function used for the solver either 'square_loss' or 'kl_loss'.
-        'kl_loss' is not implemented yet and will raise an error.
     symmetric : bool, optional
         Either C1 and C2 are to be assumed symmetric or not.
         If let to its default None value, a symmetry test will be conducted.
@@ -92,8 +91,6 @@ def semirelaxed_gromov_wasserstein(C1, C2, p=None, loss_fun='square_loss', symme
             "Semi-relaxed Gromov-Wasserstein divergence and applications on graphs"
             International Conference on Learning Representations (ICLR), 2022.
     """
-    if loss_fun == 'kl_loss':
-        raise NotImplementedError()
     arr = [C1, C2]
     if p is not None:
         arr.append(list_to_array(p))
@@ -139,7 +136,7 @@ def df(G):
             return 0.5 * (gwggrad(constC + marginal_product_1, hC1, hC2, G, nx) + gwggrad(constCt + marginal_product_2, hC1t, hC2t, G, nx))
 
     def line_search(cost, G, deltaG, Mi, cost_G, **kwargs):
-        return solve_semirelaxed_gromov_linesearch(G, deltaG, cost_G, C1, C2, ones_p, M=0., reg=1., nx=nx, **kwargs)
+        return solve_semirelaxed_gromov_linesearch(G, deltaG, cost_G, hC1, hC2, ones_p, M=0., reg=1., fC2t=fC2t, nx=nx, **kwargs)
 
     if log:
         res, log = semirelaxed_cg(p, q, 0., 1., f, df, G0, line_search, log=True, numItermax=max_iter, stopThr=tol_rel, stopThr2=tol_abs, **kwargs)
@@ -190,7 +187,6 @@ def semirelaxed_gromov_wasserstein2(C1, C2, p=None, loss_fun='square_loss', symm
         If let to its default value None, uniform distribution is taken.
     loss_fun : str
         loss function used for the solver either 'square_loss' or 'kl_loss'.
-        'kl_loss' is not implemented yet and will raise an error.
     symmetric : bool, optional
         Either C1 and C2 are to be assumed symmetric or not.
         If let to its default None value, a symmetry test will be conducted.
@@ -243,7 +239,12 @@ def semirelaxed_gromov_wasserstein2(C1, C2, p=None, loss_fun='square_loss', symm
     if loss_fun == 'square_loss':
         gC1 = 2 * C1 * nx.outer(p, p) - 2 * nx.dot(T, nx.dot(C2, T.T))
         gC2 = 2 * C2 * nx.outer(q, q) - 2 * nx.dot(T.T, nx.dot(C1, T))
-        srgw = nx.set_gradients(srgw, (C1, C2), (gC1, gC2))
+
+    elif loss_fun == 'kl_loss':
+        gC1 = nx.log(C1 + 1e-15) * nx.outer(p, p) - nx.dot(T, nx.dot(nx.log(C2 + 1e-15), T.T))
+        gC2 = nx.dot(T.T, nx.dot(C1, T)) / (C2 + 1e-15) + nx.outer(q, q)
+
+    srgw = nx.set_gradients(srgw, (C1, C2), (gC1, gC2))
 
     if log:
         return srgw, log_srgw
@@ -291,7 +292,6 @@ def semirelaxed_fused_gromov_wasserstein(
         If let to its default value None, uniform distribution is taken.
     loss_fun : str
         loss function used for the solver either 'square_loss' or 'kl_loss'.
-        'kl_loss' is not implemented yet and will raise an error.
     symmetric : bool, optional
         Either C1 and C2 are to be assumed symmetric or not.
         If let to its default None value, a symmetry test will be conducted.
@@ -332,9 +332,6 @@ def semirelaxed_fused_gromov_wasserstein(
             "Semi-relaxed Gromov-Wasserstein divergence and applications on graphs"
             International Conference on Learning Representations (ICLR), 2022.
     """
-    if loss_fun == 'kl_loss':
-        raise NotImplementedError()
-
     arr = [M, C1, C2]
     if p is not None:
         arr.append(list_to_array(p))
@@ -382,7 +379,7 @@ def df(G):
 
     def line_search(cost, G, deltaG, Mi, cost_G, **kwargs):
         return solve_semirelaxed_gromov_linesearch(
-            G, deltaG, cost_G, C1, C2, ones_p, M=(1 - alpha) * M, reg=alpha, nx=nx, **kwargs)
+            G, deltaG, cost_G, hC1, hC2, ones_p, M=(1 - alpha) * M, reg=alpha, fC2t=fC2t, nx=nx, **kwargs)
 
     if log:
         res, log = semirelaxed_cg(p, q, (1 - alpha) * M, alpha, f, df, G0, line_search, log=True, numItermax=max_iter, stopThr=tol_rel, stopThr2=tol_abs, **kwargs)
@@ -434,7 +431,6 @@ def semirelaxed_fused_gromov_wasserstein2(M, C1, C2, p=None, loss_fun='square_lo
         If let to its default value None, uniform distribution is taken.
     loss_fun : str, optional
         loss function used for the solver either 'square_loss' or 'kl_loss'.
-        'kl_loss' is not implemented yet and will raise an error.
     symmetric : bool, optional
         Either C1 and C2 are to be assumed symmetric or not.
         If let to its default None value, a symmetry test will be conducted.
@@ -494,15 +490,20 @@ def semirelaxed_fused_gromov_wasserstein2(M, C1, C2, p=None, loss_fun='square_lo
     if loss_fun == 'square_loss':
         gC1 = 2 * C1 * nx.outer(p, p) - 2 * nx.dot(T, nx.dot(C2, T.T))
         gC2 = 2 * C2 * nx.outer(q, q) - 2 * nx.dot(T.T, nx.dot(C1, T))
-        if isinstance(alpha, int) or isinstance(alpha, float):
-            srfgw_dist = nx.set_gradients(srfgw_dist, (C1, C2, M),
-                                          (alpha * gC1, alpha * gC2, (1 - alpha) * T))
-        else:
-            lin_term = nx.sum(T * M)
-            srgw_term = (srfgw_dist - (1 - alpha) * lin_term) / alpha
-            srfgw_dist = nx.set_gradients(srfgw_dist, (C1, C2, M, alpha),
-                                          (alpha * gC1, alpha * gC2, (1 - alpha) * T,
-                                           srgw_term - lin_term))
+
+    elif loss_fun == 'kl_loss':
+        gC1 = nx.log(C1 + 1e-15) * nx.outer(p, p) - nx.dot(T, nx.dot(nx.log(C2 + 1e-15), T.T))
+        gC2 = nx.dot(T.T, nx.dot(C1, T)) / (C2 + 1e-15) + nx.outer(q, q)
+
+    if isinstance(alpha, int) or isinstance(alpha, float):
+        srfgw_dist = nx.set_gradients(srfgw_dist, (C1, C2, M),
+                                      (alpha * gC1, alpha * gC2, (1 - alpha) * T))
+    else:
+        lin_term = nx.sum(T * M)
+        srgw_term = (srfgw_dist - (1 - alpha) * lin_term) / alpha
+        srfgw_dist = nx.set_gradients(srfgw_dist, (C1, C2, M, alpha),
+                                      (alpha * gC1, alpha * gC2, (1 - alpha) * T,
+                                       srgw_term - lin_term))
 
     if log:
         return srfgw_dist, log_fgw
@@ -511,7 +512,7 @@ def semirelaxed_fused_gromov_wasserstein2(M, C1, C2, p=None, loss_fun='square_lo
 
 
 def solve_semirelaxed_gromov_linesearch(G, deltaG, cost_G, C1, C2, ones_p,
-                                        M, reg, alpha_min=None, alpha_max=None, nx=None, **kwargs):
+                                        M, reg, fC2t=None, alpha_min=None, alpha_max=None, nx=None, **kwargs):
     """
     Solve the linesearch in the Conditional Gradient iterations for the semi-relaxed Gromov-Wasserstein divergence.
 
@@ -524,16 +525,22 @@ def solve_semirelaxed_gromov_linesearch(G, deltaG, cost_G, C1, C2, ones_p,
         Difference between the optimal map found by linearization in the FW algorithm and the value at a given iteration
     cost_G : float
         Value of the cost at `G`
-    C1 : array-like (ns,ns)
-        Structure matrix in the source domain.
-    C2 : array-like (nt,nt)
-        Structure matrix in the target domain.
+    C1 : array-like (ns,ns), optional
+        Transformed Structure matrix in the source domain.
+        Note that for the 'square_loss' and 'kl_loss', we provide hC1 from ot.gromov.init_matrix_semirelaxed
+    C2 : array-like (nt,nt), optional
+        Transformed Structure matrix in the source domain.
+        Note that for the 'square_loss' and 'kl_loss', we provide hC2 from ot.gromov.init_matrix_semirelaxed
     ones_p: array-like (ns,1)
         Array of ones of size ns
     M : array-like (ns,nt)
         Cost matrix between the features.
     reg : float
         Regularization parameter.
+    fC2t: array-like (nt,nt), optional
+        Transformed Structure matrix in the source domain.
+        Note that for the 'square_loss' and 'kl_loss', we provide fC2t from ot.gromov.init_matrix_semirelaxed.
+        If fC2t is not provided, it is by default fC2t corresponding to the 'square_loss'.
     alpha_min : float, optional
         Minimum value for alpha
     alpha_max : float, optional
@@ -565,11 +572,14 @@ def solve_semirelaxed_gromov_linesearch(G, deltaG, cost_G, C1, C2, ones_p,
 
     qG, qdeltaG = nx.sum(G, 0), nx.sum(deltaG, 0)
     dot = nx.dot(nx.dot(C1, deltaG), C2.T)
-    C2t_square = C2.T ** 2
-    dot_qG = nx.dot(nx.outer(ones_p, qG), C2t_square)
-    dot_qdeltaG = nx.dot(nx.outer(ones_p, qdeltaG), C2t_square)
-    a = reg * nx.sum((dot_qdeltaG - 2 * dot) * deltaG)
-    b = nx.sum(M * deltaG) + reg * (nx.sum((dot_qdeltaG - 2 * dot) * G) + nx.sum((dot_qG - 2 * nx.dot(nx.dot(C1, G), C2.T)) * deltaG))
+    if fC2t is None:
+        fC2t = C2.T ** 2
+    dot_qG = nx.dot(nx.outer(ones_p, qG), fC2t)
+    dot_qdeltaG = nx.dot(nx.outer(ones_p, qdeltaG), fC2t)
+
+    a = reg * nx.sum((dot_qdeltaG - dot) * deltaG)
+    b = nx.sum(M * deltaG) + reg * (nx.sum((dot_qdeltaG - dot) * G) + nx.sum((dot_qG - nx.dot(nx.dot(C1, G), C2.T)) * deltaG))
+
     alpha = solve_1d_linesearch_quad(a, b)
     if alpha_min is not None or alpha_max is not None:
         alpha = np.clip(alpha, alpha_min, alpha_max)
@@ -620,7 +630,6 @@ def entropic_semirelaxed_gromov_wasserstein(
         If let to its default value None, uniform distribution is taken.
     loss_fun : str
         loss function used for the solver either 'square_loss' or 'kl_loss'.
-        'kl_loss' is not implemented yet and will raise an error.
     epsilon : float
         Regularization term >0
     symmetric : bool, optional
@@ -655,8 +664,6 @@ def entropic_semirelaxed_gromov_wasserstein(
             "Semi-relaxed Gromov-Wasserstein divergence and applications on graphs"
             International Conference on Learning Representations (ICLR), 2022.
     """
-    if loss_fun == 'kl_loss':
-        raise NotImplementedError()
     arr = [C1, C2]
     if p is not None:
         arr.append(list_to_array(p))
@@ -777,7 +784,6 @@ def entropic_semirelaxed_gromov_wasserstein2(
         If let to its default value None, uniform distribution is taken.
     loss_fun : str
         loss function used for the solver either 'square_loss' or 'kl_loss'.
-        'kl_loss' is not implemented yet and will raise an error.
     epsilon : float
         Regularization term >0
     symmetric : bool, optional
@@ -869,7 +875,6 @@ def entropic_semirelaxed_fused_gromov_wasserstein(
         If let to its default value None, uniform distribution is taken.
     loss_fun : str
         loss function used for the solver either 'square_loss' or 'kl_loss'.
-        'kl_loss' is not implemented yet and will raise an error.
     epsilon : float
         Regularization term >0
     symmetric : bool, optional
@@ -907,8 +912,6 @@ def entropic_semirelaxed_fused_gromov_wasserstein(
             "Semi-relaxed Gromov-Wasserstein divergence and applications on graphs"
             International Conference on Learning Representations (ICLR), 2022.
     """
-    if loss_fun == 'kl_loss':
-        raise NotImplementedError()
     arr = [M, C1, C2]
     if p is not None:
         arr.append(list_to_array(p))
@@ -1032,7 +1035,6 @@ def entropic_semirelaxed_fused_gromov_wasserstein2(
         If let to its default value None, uniform distribution is taken.
     loss_fun : str, optional
         loss function used for the solver either 'square_loss' or 'kl_loss'.
-        'kl_loss' is not implemented yet and will raise an error.
     epsilon : float
         Regularization term >0
     symmetric : bool, optional

ot/gromov/_utils.py

@@ -399,6 +399,19 @@ def init_matrix_semirelaxed(C1, C2, p, loss_fun='square_loss', nx=None):
 
                         h_2(b) &= 2b
 
+    The kl-loss function :math:`L(a, b) = a \log\left(\frac{a}{b}\right) - a + b` is read as :
+
+    .. math::
+
+        L(a, b) = f_1(a) + f_2(b) - h_1(a) h_2(b)
+
+        \mathrm{with} \ f_1(a) &= a \log(a) - a
+
+                        f_2(b) &= b
+
+                        h_1(a) &= a
+
+                        h_2(b) &= \log(b)
     Parameters
     ----------
     C1 : array-like, shape (ns, ns)
@@ -451,9 +464,19 @@ def h1(a):
         def h2(b):
             return 2 * b
     elif loss_fun == 'kl_loss':
-        raise NotImplementedError()
+        def f1(a):
+            return a * nx.log(a + 1e-15) - a
+
+        def f2(b):
+            return b
+
+        def h1(a):
+            return a
+
+        def h2(b):
+            return nx.log(b + 1e-15)
     else:
-        raise ValueError(f"Unknown `loss_fun='{loss_fun}'`. Only 'square_loss' is supported.")
+        raise ValueError(f"Unknown `loss_fun='{loss_fun}'`. Use one of: {'square_loss', 'kl_loss'}.")
 
     constC = nx.dot(nx.dot(f1(C1), nx.reshape(p, (-1, 1))),
                     nx.ones((1, C2.shape[0]), type_as=p))