[MRG] Adding greenkhorn

README.md

@@ -14,10 +14,10 @@ This open source Python library provide several solvers for optimization problem
 It provides the following solvers:
 
 * OT Network Flow solver for the linear program/ Earth Movers Distance [1].
-* Entropic regularization OT solver with Sinkhorn Knopp Algorithm [2] and stabilized version [9][10] with optional GPU implementation (requires cudamat).
+* Entropic regularization OT solver with Sinkhorn Knopp Algorithm [2] and stabilized version [9][10] and greedy SInkhorn [22] with optional GPU implementation (requires cudamat).
 * Smooth optimal transport solvers (dual and semi-dual) for KL and squared L2 regularizations [17].
 * Non regularized Wasserstein barycenters [16] with LP solver (only small scale).
-* Bregman projections for Wasserstein barycenter [3] and unmixing [4].
+* Bregman projections for Wasserstein barycenter [3], convolutional barycenter [21] and unmixing [4].
 * Optimal transport for domain adaptation with group lasso regularization [5]
 * Conditional gradient [6] and Generalized conditional gradient for regularized OT [7].
 * Linear OT [14] and Joint OT matrix and mapping estimation [8].
@@ -165,6 +165,7 @@ The contributors to this library are:
 * [Antoine Rolet](https://arolet.github.io/)
 * Erwan Vautier (Gromov-Wasserstein)
 * [Kilian Fatras](https://kilianfatras.github.io/)
+* [Alain Rakotomamonjy](https://sites.google.com/site/alainrakotomamonjy/home)
 
 This toolbox benefit a lot from open source research and we would like to thank the following persons for providing some code (in various languages):
 
@@ -230,3 +231,5 @@ You can also post bug reports and feature requests in Github issues. Make sure t
 [20] Cuturi, M. and Doucet, A. (2014) [Fast Computation of Wasserstein Barycenters](http://proceedings.mlr.press/v32/cuturi14.html). International Conference in Machine Learning
 
 [21] Solomon, J., De Goes, F., Peyré, G., Cuturi, M., Butscher, A., Nguyen, A. & Guibas, L. (2015). [Convolutional wasserstein distances: Efficient optimal transportation on geometric domains](https://dl.acm.org/citation.cfm?id=2766963). ACM Transactions on Graphics (TOG), 34(4), 66.
+
+[22] J. Altschuler, J.Weed, P. Rigollet, (2017) [Near-linear time approximation algorithms for optimal transport via Sinkhorn iteration](https://papers.nips.cc/paper/6792-near-linear-time-approximation-algorithms-for-optimal-transport-via-sinkhorn-iteration.pdf), Advances in Neural Information Processing Systems (NIPS) 31

docs/source/readme.rst

@@ -13,13 +13,14 @@ It provides the following solvers:
 -  OT Network Flow solver for the linear program/ Earth Movers Distance
    [1].
 -  Entropic regularization OT solver with Sinkhorn Knopp Algorithm [2]
-   and stabilized version [9][10] with optional GPU implementation
-   (requires cudamat).
+   and stabilized version [9][10] and greedy SInkhorn [22] with optional
+   GPU implementation (requires cudamat).
 -  Smooth optimal transport solvers (dual and semi-dual) for KL and
    squared L2 regularizations [17].
 -  Non regularized Wasserstein barycenters [16] with LP solver (only
    small scale).
--  Bregman projections for Wasserstein barycenter [3] and unmixing [4].
+-  Bregman projections for Wasserstein barycenter [3], convolutional
+   barycenter [21] and unmixing [4].
 -  Optimal transport for domain adaptation with group lasso
    regularization [5]
 -  Conditional gradient [6] and Generalized conditional gradient for
@@ -29,6 +30,9 @@ It provides the following solvers:
    pymanopt).
 -  Gromov-Wasserstein distances and barycenters ([13] and regularized
    [12])
+-  Stochastic Optimization for Large-scale Optimal Transport (semi-dual
+   problem [18] and dual problem [19])
+-  Non regularized free support Wasserstein barycenters [20].
 
 Some demonstrations (both in Python and Jupyter Notebook format) are
 available in the examples folder.
@@ -219,6 +223,9 @@ The contributors to this library are:
 -  `Stanislas Chambon <https://slasnista.github.io/>`__
 -  `Antoine Rolet <https://arolet.github.io/>`__
 -  Erwan Vautier (Gromov-Wasserstein)
+-  `Kilian Fatras <https://kilianfatras.github.io/>`__
+-  `Alain
+   Rakotomamonjy <https://sites.google.com/site/alainrakotomamonjy/home>`__
 
 This toolbox benefit a lot from open source research and we would like
 to thank the following persons for providing some code (in various
@@ -334,6 +341,31 @@ Optimal Transport <https://arxiv.org/abs/1710.06276>`__. Proceedings of
 the Twenty-First International Conference on Artificial Intelligence and
 Statistics (AISTATS).
 
+[18] Genevay, A., Cuturi, M., Peyré, G. & Bach, F. (2016) `Stochastic
+Optimization for Large-scale Optimal
+Transport <https://arxiv.org/abs/1605.08527>`__. Advances in Neural
+Information Processing Systems (2016).
+
+[19] Seguy, V., Bhushan Damodaran, B., Flamary, R., Courty, N., Rolet,
+A.& Blondel, M. `Large-scale Optimal Transport and Mapping
+Estimation <https://arxiv.org/pdf/1711.02283.pdf>`__. International
+Conference on Learning Representation (2018)
+
+[20] Cuturi, M. and Doucet, A. (2014) `Fast Computation of Wasserstein
+Barycenters <http://proceedings.mlr.press/v32/cuturi14.html>`__.
+International Conference in Machine Learning
+
+[21] Solomon, J., De Goes, F., Peyré, G., Cuturi, M., Butscher, A.,
+Nguyen, A. & Guibas, L. (2015). `Convolutional wasserstein distances:
+Efficient optimal transportation on geometric
+domains <https://dl.acm.org/citation.cfm?id=2766963>`__. ACM
+Transactions on Graphics (TOG), 34(4), 66.
+
+[22] J. Altschuler, J.Weed, P. Rigollet, (2017) `Near-linear time
+approximation algorithms for optimal transport via Sinkhorn
+iteration <https://papers.nips.cc/paper/6792-near-linear-time-approximation-algorithms-for-optimal-transport-via-sinkhorn-iteration.pdf>`__,
+Advances in Neural Information Processing Systems (NIPS) 31
+
 .. |PyPI version| image:: https://badge.fury.io/py/POT.svg
    :target: https://badge.fury.io/py/POT
 .. |Anaconda Cloud| image:: https://anaconda.org/conda-forge/pot/badges/version.svg

ot/bregman.py

@@ -47,7 +47,7 @@ def sinkhorn(a, b, M, reg, method='sinkhorn', numItermax=1000,
     reg : float
         Regularization term >0
     method : str
-        method used for the solver either 'sinkhorn',  'sinkhorn_stabilized' or
+        method used for the solver either 'sinkhorn', 'greenkhorn', 'sinkhorn_stabilized' or
         'sinkhorn_epsilon_scaling', see those function for specific parameters
     numItermax : int, optional
         Max number of iterations
@@ -103,6 +103,10 @@ def sinkhorn(a, b, M, reg, method='sinkhorn', numItermax=1000,
         def sink():
             return sinkhorn_knopp(a, b, M, reg, numItermax=numItermax,
                                   stopThr=stopThr, verbose=verbose, log=log, **kwargs)
+    elif method.lower() == 'greenkhorn':
+        def sink():
+            return greenkhorn(a, b, M, reg, numItermax=numItermax,
+                              stopThr=stopThr, verbose=verbose, log=log)
     elif method.lower() == 'sinkhorn_stabilized':
         def sink():
             return sinkhorn_stabilized(a, b, M, reg, numItermax=numItermax,
@@ -197,13 +201,16 @@ def sinkhorn2(a, b, M, reg, method='sinkhorn', numItermax=1000,
 
     .. [10] Chizat, L., Peyré, G., Schmitzer, B., & Vialard, F. X. (2016). Scaling algorithms for unbalanced transport problems. arXiv preprint arXiv:1607.05816.
 
+       [21] Altschuler J., Weed J., Rigollet P. : Near-linear time approximation algorithms for optimal transport via Sinkhorn iteration, Advances in Neural Information Processing Systems (NIPS) 31, 2017
+
 
 
     See Also
     --------
     ot.lp.emd : Unregularized OT
     ot.optim.cg : General regularized OT
     ot.bregman.sinkhorn_knopp : Classic Sinkhorn [2]
+    ot.bregman.greenkhorn : Greenkhorn [21]
     ot.bregman.sinkhorn_stabilized: Stabilized sinkhorn [9][10]
     ot.bregman.sinkhorn_epsilon_scaling: Sinkhorn with epslilon scaling [9][10]
 
@@ -410,6 +417,148 @@ def sinkhorn_knopp(a, b, M, reg, numItermax=1000,
             return u.reshape((-1, 1)) * K * v.reshape((1, -1))
 
 
+def greenkhorn(a, b, M, reg, numItermax=10000, stopThr=1e-9, verbose=False, log=False):
+    """
+    Solve the entropic regularization optimal transport problem and return the OT matrix
+
+    The algorithm used is based on the paper
+
+    Near-linear time approximation algorithms for optimal transport via Sinkhorn iteration
+        by Jason Altschuler, Jonathan Weed, Philippe Rigollet
+        appeared at NIPS 2017
+
+    which is a stochastic version of the Sinkhorn-Knopp algorithm [2].
+
+    The function solves the following optimization problem:
+
+    .. math::
+        \gamma = arg\min_\gamma <\gamma,M>_F + reg\cdot\Omega(\gamma)
+
+        s.t. \gamma 1 = a
+
+             \gamma^T 1= b
+
+             \gamma\geq 0
+    where :
+
+    - M is the (ns,nt) metric cost matrix
+    - :math:`\Omega` is the entropic regularization term :math:`\Omega(\gamma)=\sum_{i,j} \gamma_{i,j}\log(\gamma_{i,j})`
+    - a and b are source and target weights (sum to 1)
+
+
+
+    Parameters
+    ----------
+    a : np.ndarray (ns,)
+        samples weights in the source domain
+    b : np.ndarray (nt,) or np.ndarray (nt,nbb)
+        samples in the target domain, compute sinkhorn with multiple targets
+        and fixed M if b is a matrix (return OT loss + dual variables in log)
+    M : np.ndarray (ns,nt)
+        loss matrix
+    reg : float
+        Regularization term >0
+    numItermax : int, optional
+        Max number of iterations
+    stopThr : float, optional
+        Stop threshol on error (>0)
+    log : bool, optional
+        record log if True
+
+
+    Returns
+    -------
+    gamma : (ns x nt) ndarray
+        Optimal transportation matrix for the given parameters
+    log : dict
+        log dictionary return only if log==True in parameters
+
+    Examples
+    --------
+
+    >>> import ot
+    >>> a=[.5,.5]
+    >>> b=[.5,.5]
+    >>> M=[[0.,1.],[1.,0.]]
+    >>> ot.bregman.greenkhorn(a,b,M,1)
+    array([[ 0.36552929,  0.13447071],
+           [ 0.13447071,  0.36552929]])
+
+
+    References
+    ----------
+
+    .. [2] M. Cuturi, Sinkhorn Distances : Lightspeed Computation of Optimal Transport, Advances in Neural Information Processing Systems (NIPS) 26, 2013
+       [22] J. Altschuler, J.Weed, P. Rigollet : Near-linear time approximation algorithms for optimal transport via Sinkhorn iteration, Advances in Neural Information Processing Systems (NIPS) 31, 2017
+
+
+    See Also
+    --------
+    ot.lp.emd : Unregularized OT
+    ot.optim.cg : General regularized OT
+
+    """
+
+    n = a.shape[0]
+    m = b.shape[0]
+
+    # Next 3 lines equivalent to K= np.exp(-M/reg), but faster to compute
+    K = np.empty_like(M)
+    np.divide(M, -reg, out=K)
+    np.exp(K, out=K)
+
+    u = np.full(n, 1. / n)
+    v = np.full(m, 1. / m)
+    G = u[:, np.newaxis] * K * v[np.newaxis, :]
+
+    viol = G.sum(1) - a
+    viol_2 = G.sum(0) - b
+    stopThr_val = 1
+    if log:
+        log['u'] = u
+        log['v'] = v
+
+    for i in range(numItermax):
+        i_1 = np.argmax(np.abs(viol))
+        i_2 = np.argmax(np.abs(viol_2))
+        m_viol_1 = np.abs(viol[i_1])
+        m_viol_2 = np.abs(viol_2[i_2])
+        stopThr_val = np.maximum(m_viol_1, m_viol_2)
+
+        if m_viol_1 > m_viol_2:
+            old_u = u[i_1]
+            u[i_1] = a[i_1] / (K[i_1, :].dot(v))
+            G[i_1, :] = u[i_1] * K[i_1, :] * v
+
+            viol[i_1] = u[i_1] * K[i_1, :].dot(v) - a[i_1]
+            viol_2 += (K[i_1, :].T * (u[i_1] - old_u) * v)
+
+        else:
+            old_v = v[i_2]
+            v[i_2] = b[i_2] / (K[:, i_2].T.dot(u))
+            G[:, i_2] = u * K[:, i_2] * v[i_2]
+            #aviol = (G@one_m - a)
+            #aviol_2 = (G.T@one_n - b)
+            viol += (-old_v + v[i_2]) * K[:, i_2] * u
+            viol_2[i_2] = v[i_2] * K[:, i_2].dot(u) - b[i_2]
+
+            #print('b',np.max(abs(aviol -viol)),np.max(abs(aviol_2 - viol_2)))
+
+        if stopThr_val <= stopThr:
+            break
+    else:
+        print('Warning: Algorithm did not converge')
+
+    if log:
+        log['u'] = u
+        log['v'] = v
+
+    if log:
+        return G, log
+    else:
+        return G
+
+
 def sinkhorn_stabilized(a, b, M, reg, numItermax=1000, tau=1e3, stopThr=1e-9,
                         warmstart=None, verbose=False, print_period=20, log=False, **kwargs):
     """

test/test_bregman.py

@@ -71,11 +71,14 @@ def test_sinkhorn_variants():
     Ges = ot.sinkhorn(
         u, u, M, 1, method='sinkhorn_epsilon_scaling', stopThr=1e-10)
     Gerr = ot.sinkhorn(u, u, M, 1, method='do_not_exists', stopThr=1e-10)
+    G_green = ot.sinkhorn(u, u, M, 1, method='greenkhorn', stopThr=1e-10)
 
     # check values
     np.testing.assert_allclose(G0, Gs, atol=1e-05)
     np.testing.assert_allclose(G0, Ges, atol=1e-05)
     np.testing.assert_allclose(G0, Gerr)
+    np.testing.assert_allclose(G0, G_green, atol=1e-5)
+    print(G0, G_green)
 
 
 def test_bary():