ot.partial

Partial OT solvers

Functions

ot.partial.entropic_partial_gromov_wasserstein(C1, C2, p, q, reg, m=None, G0=None, numItermax=1000, tol=1e-07, log=False, verbose=False)[source]

Returns the partial Gromov-Wasserstein transport between \((\mathbf{C_1}, \mathbf{p})\) and \((\mathbf{C_2}, \mathbf{q})\)

The function solves the following optimization problem:

\[\gamma = \mathop{\arg \min}_{\gamma} \quad \sum_{i,j,k,l} L(\mathbf{C_1}_{i,k}, \mathbf{C_2}_{j,l})\cdot \gamma_{i,j}\cdot\gamma_{k,l} + \mathrm{reg} \cdot\Omega(\gamma)\]
\[ \begin{align}\begin{aligned}s.t. \ \gamma &\geq 0\\ \gamma \mathbf{1} &\leq \mathbf{a}\\ \gamma^T \mathbf{1} &\leq \mathbf{b}\\ \mathbf{1}^T \gamma^T \mathbf{1} = m &\leq \min\{\|\mathbf{a}\|_1, \|\mathbf{b}\|_1\}\end{aligned}\end{align} \]

where :

  • \(\mathbf{C_1}\) is the metric cost matrix in the source space

  • \(\mathbf{C_2}\) is the metric cost matrix in the target space

  • \(\mathbf{p}\) and \(\mathbf{q}\) are the sample weights

  • L: quadratic loss function

  • \(\Omega\) is the entropic regularization term, \(\Omega=\sum_{i,j} \gamma_{i,j}\log(\gamma_{i,j})\)

  • m is the amount of mass to be transported

The formulation of the GW problem has been proposed in [12] and the partial GW in [29]

Parameters
  • C1 (ndarray, shape (ns, ns)) – Metric cost matrix in the source space

  • C2 (ndarray, shape (nt, nt)) – Metric costfr matrix in the target space

  • p (ndarray, shape (ns,)) – Distribution in the source space

  • q (ndarray, shape (nt,)) – Distribution in the target space

  • reg (float) – entropic regularization parameter

  • m (float, optional) – Amount of mass to be transported (default: \(\min\{\|\mathbf{p}\|_1, \|\mathbf{q}\|_1\}\))

  • G0 (ndarray, shape (ns, nt), optional) – Initialisation of the transportation matrix

  • numItermax (int, optional) – Max number of iterations

  • tol (float, optional) – Stop threshold on error (>0)

  • log (bool, optional) – return log if True

  • verbose (bool, optional) – Print information along iterations

Examples

>>> import ot
>>> import scipy as sp
>>> a = np.array([0.25] * 4)
>>> b = np.array([0.25] * 4)
>>> x = np.array([1,2,100,200]).reshape((-1,1))
>>> y = np.array([3,2,98,199]).reshape((-1,1))
>>> C1 = sp.spatial.distance.cdist(x, x)
>>> C2 = sp.spatial.distance.cdist(y, y)
>>> np.round(entropic_partial_gromov_wasserstein(C1, C2, a, b, 50), 2)
array([[0.12, 0.13, 0.  , 0.  ],
       [0.13, 0.12, 0.  , 0.  ],
       [0.  , 0.  , 0.25, 0.  ],
       [0.  , 0.  , 0.  , 0.25]])
>>> np.round(entropic_partial_gromov_wasserstein(C1, C2, a, b, 50,0.25), 2)
array([[0.02, 0.03, 0.  , 0.03],
       [0.03, 0.03, 0.  , 0.03],
       [0.  , 0.  , 0.03, 0.  ],
       [0.02, 0.02, 0.  , 0.03]])
Returns

  • math: gamma : (dim_a, dim_b) ndarray – Optimal transportation matrix for the given parameters

  • log (dict) – log dictionary returned only if log is True

References

12

Peyré, Gabriel, Marco Cuturi, and Justin Solomon, “Gromov-Wasserstein averaging of kernel and distance matrices.” International Conference on Machine Learning (ICML). 2016.

29

Chapel, L., Alaya, M., Gasso, G. (2020). “Partial Optimal Transport with Applications on Positive-Unlabeled Learning”. NeurIPS.

See also

ot.partial.partial_gromov_wasserstein

exact Partial Gromov-Wasserstein

Examples using ot.partial.entropic_partial_gromov_wasserstein

ot.partial.entropic_partial_gromov_wasserstein2(C1, C2, p, q, reg, m=None, G0=None, numItermax=1000, tol=1e-07, log=False, verbose=False)[source]

Returns the partial Gromov-Wasserstein discrepancy between \((\mathbf{C_1}, \mathbf{p})\) and \((\mathbf{C_2}, \mathbf{q})\)

The function solves the following optimization problem:

\[GW = \min_{\gamma} \quad \sum_{i,j,k,l} L(\mathbf{C_1}_{i,k}, \mathbf{C_2}_{j,l})\cdot \gamma_{i,j}\cdot\gamma_{k,l} + \mathrm{reg} \cdot\Omega(\gamma)\]
\[ \begin{align}\begin{aligned}s.t. \ \gamma &\geq 0\\ \gamma \mathbf{1} &\leq \mathbf{a}\\ \gamma^T \mathbf{1} &\leq \mathbf{b}\\ \mathbf{1}^T \gamma^T \mathbf{1} = m &\leq \min\{\|\mathbf{a}\|_1, \|\mathbf{b}\|_1\}\end{aligned}\end{align} \]

where :

  • \(\mathbf{C_1}\) is the metric cost matrix in the source space

  • \(\mathbf{C_2}\) is the metric cost matrix in the target space

  • \(\mathbf{p}\) and \(\mathbf{q}\) are the sample weights

  • L : quadratic loss function

  • \(\Omega\) is the entropic regularization term, \(\Omega=\sum_{i,j} \gamma_{i,j}\log(\gamma_{i,j})\)

  • m is the amount of mass to be transported

The formulation of the GW problem has been proposed in [12] and the partial GW in [29]

Parameters
  • C1 (ndarray, shape (ns, ns)) – Metric cost matrix in the source space

  • C2 (ndarray, shape (nt, nt)) – Metric costfr matrix in the target space

  • p (ndarray, shape (ns,)) – Distribution in the source space

  • q (ndarray, shape (nt,)) – Distribution in the target space

  • reg (float) – entropic regularization parameter

  • m (float, optional) – Amount of mass to be transported (default: \(\min\{\|\mathbf{p}\|_1, \|\mathbf{q}\|_1\}\))

  • G0 (ndarray, shape (ns, nt), optional) – Initialisation of the transportation matrix

  • numItermax (int, optional) – Max number of iterations

  • tol (float, optional) – Stop threshold on error (>0)

  • log (bool, optional) – return log if True

  • verbose (bool, optional) – Print information along iterations

Returns

  • partial_gw_dist (float) – Gromov-Wasserstein distance

  • log (dict) – log dictionary returned only if log is True

Examples

>>> import ot
>>> import scipy as sp
>>> a = np.array([0.25] * 4)
>>> b = np.array([0.25] * 4)
>>> x = np.array([1,2,100,200]).reshape((-1,1))
>>> y = np.array([3,2,98,199]).reshape((-1,1))
>>> C1 = sp.spatial.distance.cdist(x, x)
>>> C2 = sp.spatial.distance.cdist(y, y)
>>> np.round(entropic_partial_gromov_wasserstein2(C1, C2, a, b,50), 2)
1.87

References

12

Peyré, Gabriel, Marco Cuturi, and Justin Solomon, “Gromov-Wasserstein averaging of kernel and distance matrices.” International Conference on Machine Learning (ICML). 2016.

29

Chapel, L., Alaya, M., Gasso, G. (2020). “Partial Optimal Transport with Applications on Positive-Unlabeled Learning”. NeurIPS.

ot.partial.entropic_partial_wasserstein(a, b, M, reg, m=None, numItermax=1000, stopThr=1e-100, verbose=False, log=False)[source]

Solves the partial optimal transport problem and returns the OT plan

The function considers the following problem:

\[ \begin{align}\begin{aligned}\gamma = \mathop{\arg \min}_\gamma \quad \langle \gamma, \mathbf{M} \rangle_F + \mathrm{reg} \cdot\Omega(\gamma)\\\begin{split}s.t. \gamma \mathbf{1} &\leq \mathbf{a} \\ \gamma^T \mathbf{1} &\leq \mathbf{b} \\ \gamma &\geq 0 \\ \mathbf{1}^T \gamma^T \mathbf{1} = m &\leq \min\{\|\mathbf{a}\|_1, \|\mathbf{b}\|_1\} \\\end{split}\end{aligned}\end{align} \]

where :

  • \(\mathbf{M}\) is the metric cost matrix

  • \(\Omega\) is the entropic regularization term, \(\Omega=\sum_{i,j} \gamma_{i,j}\log(\gamma_{i,j})\)

  • \(\mathbf{a}\) and \(\mathbf{b}\) are the sample weights

  • m is the amount of mass to be transported

The formulation of the problem has been proposed in [3] (prop. 5)

Parameters
  • a (np.ndarray (dim_a,)) – Unnormalized histogram of dimension dim_a

  • b (np.ndarray (dim_b,)) – Unnormalized histograms of dimension dim_b

  • M (np.ndarray (dim_a, dim_b)) – cost matrix

  • reg (float) – Regularization term > 0

  • m (float, optional) – Amount of mass to be transported

  • numItermax (int, optional) – Max number of iterations

  • stopThr (float, optional) – Stop threshold on error (>0)

  • verbose (bool, optional) – Print information along iterations

  • log (bool, optional) – record log if True

Returns

  • gamma ((dim_a, dim_b) ndarray) – Optimal transportation matrix for the given parameters

  • log (dict) – log dictionary returned only if log is True

Examples

>>> import ot
>>> a = [.1, .2]
>>> b = [.1, .1]
>>> M = [[0., 1.], [2., 3.]]
>>> np.round(entropic_partial_wasserstein(a, b, M, 1, 0.1), 2)
array([[0.06, 0.02],
       [0.01, 0.  ]])

References

3

Benamou, J. D., Carlier, G., Cuturi, M., Nenna, L., & Peyré, G. (2015). Iterative Bregman projections for regularized transportation problems. SIAM Journal on Scientific Computing, 37(2), A1111-A1138.

See also

ot.partial.partial_wasserstein

exact Partial Wasserstein

Examples using ot.partial.entropic_partial_wasserstein

ot.partial.gwgrad_partial(C1, C2, T)[source]

Compute the GW gradient. Note: we can not use the trick in [12] as the marginals may not sum to 1.

Parameters
  • C1 (array of shape (n_p,n_p)) – intra-source (P) cost matrix

  • C2 (array of shape (n_u,n_u)) – intra-target (U) cost matrix

  • T (array of shape(n_p+nb_dummies, n_u) (default: None)) – Transport matrix

Returns

gradient

Return type

numpy.array of shape (n_p+nb_dummies, n_u)

References

12

Peyré, Gabriel, Marco Cuturi, and Justin Solomon, “Gromov-Wasserstein averaging of kernel and distance matrices.” International Conference on Machine Learning (ICML). 2016.

ot.partial.gwloss_partial(C1, C2, T)[source]

Compute the GW loss.

Parameters
  • C1 (array of shape (n_p,n_p)) – intra-source (P) cost matrix

  • C2 (array of shape (n_u,n_u)) – intra-target (U) cost matrix

  • T (array of shape(n_p+nb_dummies, n_u) (default: None)) – Transport matrix

Return type

GW loss

ot.partial.partial_gromov_wasserstein(C1, C2, p, q, m=None, nb_dummies=1, G0=None, thres=1, numItermax=1000, tol=1e-07, log=False, verbose=False, **kwargs)[source]

Solves the partial optimal transport problem and returns the OT plan

The function considers the following problem:

\[\gamma = \mathop{\arg \min}_\gamma \quad \langle \gamma, \mathbf{M} \rangle_F\]
\[ \begin{align}\begin{aligned}s.t. \ \gamma \mathbf{1} &\leq \mathbf{a}\\ \gamma^T \mathbf{1} &\leq \mathbf{b}\\ \gamma &\geq 0\\ \mathbf{1}^T \gamma^T \mathbf{1} = m &\leq \min\{\|\mathbf{a}\|_1, \|\mathbf{b}\|_1\}\end{aligned}\end{align} \]

where :

  • \(\mathbf{M}\) is the metric cost matrix

  • \(\Omega\) is the entropic regularization term, \(\Omega(\gamma) = \sum_{i,j} \gamma_{i,j}\log(\gamma_{i,j})\)

  • \(\mathbf{a}\) and \(\mathbf{b}\) are the sample weights

  • m is the amount of mass to be transported

The formulation of the problem has been proposed in [29]

Parameters
  • C1 (ndarray, shape (ns, ns)) – Metric cost matrix in the source space

  • C2 (ndarray, shape (nt, nt)) – Metric costfr matrix in the target space

  • p (ndarray, shape (ns,)) – Distribution in the source space

  • q (ndarray, shape (nt,)) – Distribution in the target space

  • m (float, optional) – Amount of mass to be transported (default: \(\min\{\|\mathbf{p}\|_1, \|\mathbf{q}\|_1\}\))

  • nb_dummies (int, optional) – Number of dummy points to add (avoid instabilities in the EMD solver)

  • G0 (ndarray, shape (ns, nt), optional) – Initialisation of the transportation matrix

  • thres (float, optional) – quantile of the gradient matrix to populate the cost matrix when 0 (default: 1)

  • numItermax (int, optional) – Max number of iterations

  • tol (float, optional) – tolerance for stopping iterations

  • log (bool, optional) – return log if True

  • verbose (bool, optional) – Print information along iterations

  • **kwargs (dict) – parameters can be directly passed to the emd solver

Returns

  • gamma ((dim_a, dim_b) ndarray) – Optimal transportation matrix for the given parameters

  • log (dict) – log dictionary returned only if log is True

Examples

>>> import ot
>>> import scipy as sp
>>> a = np.array([0.25] * 4)
>>> b = np.array([0.25] * 4)
>>> x = np.array([1,2,100,200]).reshape((-1,1))
>>> y = np.array([3,2,98,199]).reshape((-1,1))
>>> C1 = sp.spatial.distance.cdist(x, x)
>>> C2 = sp.spatial.distance.cdist(y, y)
>>> np.round(partial_gromov_wasserstein(C1, C2, a, b),2)
array([[0.  , 0.25, 0.  , 0.  ],
       [0.25, 0.  , 0.  , 0.  ],
       [0.  , 0.  , 0.25, 0.  ],
       [0.  , 0.  , 0.  , 0.25]])
>>> np.round(partial_gromov_wasserstein(C1, C2, a, b, m=0.25),2)
array([[0.  , 0.  , 0.  , 0.  ],
       [0.  , 0.  , 0.  , 0.  ],
       [0.  , 0.  , 0.25, 0.  ],
       [0.  , 0.  , 0.  , 0.  ]])

References

29

Chapel, L., Alaya, M., Gasso, G. (2020). “Partial Optimal Transport with Applications on Positive-Unlabeled Learning”. NeurIPS.

Examples using ot.partial.partial_gromov_wasserstein

ot.partial.partial_gromov_wasserstein2(C1, C2, p, q, m=None, nb_dummies=1, G0=None, thres=1, numItermax=1000, tol=1e-07, log=False, verbose=False, **kwargs)[source]

Solves the partial optimal transport problem and returns the partial Gromov-Wasserstein discrepancy

The function considers the following problem:

\[GW = \min_\gamma \quad \langle \gamma, \mathbf{M} \rangle_F\]
\[ \begin{align}\begin{aligned}s.t. \ \gamma \mathbf{1} &\leq \mathbf{a}\\ \gamma^T \mathbf{1} &\leq \mathbf{b}\\ \gamma &\geq 0\\ \mathbf{1}^T \gamma^T \mathbf{1} = m &\leq \min\{\|\mathbf{a}\|_1, \|\mathbf{b}\|_1\}\end{aligned}\end{align} \]

where :

  • \(\mathbf{M}\) is the metric cost matrix

  • \(\Omega\) is the entropic regularization term, \(\Omega(\gamma) = \sum_{i,j} \gamma_{i,j}\log(\gamma_{i,j})\)

  • \(\mathbf{a}\) and \(\mathbf{b}\) are the sample weights

  • m is the amount of mass to be transported

The formulation of the problem has been proposed in [29]

Parameters
  • C1 (ndarray, shape (ns, ns)) – Metric cost matrix in the source space

  • C2 (ndarray, shape (nt, nt)) – Metric costfr matrix in the target space

  • p (ndarray, shape (ns,)) – Distribution in the source space

  • q (ndarray, shape (nt,)) – Distribution in the target space

  • m (float, optional) – Amount of mass to be transported (default: \(\min\{\|\mathbf{p}\|_1, \|\mathbf{q}\|_1\}\))

  • nb_dummies (int, optional) – Number of dummy points to add (avoid instabilities in the EMD solver)

  • G0 (ndarray, shape (ns, nt), optional) – Initialisation of the transportation matrix

  • thres (float, optional) – quantile of the gradient matrix to populate the cost matrix when 0 (default: 1)

  • numItermax (int, optional) – Max number of iterations

  • tol (float, optional) – tolerance for stopping iterations

  • log (bool, optional) – return log if True

  • verbose (bool, optional) – Print information along iterations

  • **kwargs (dict) – parameters can be directly passed to the emd solver

Warning

When dealing with a large number of points, the EMD solver may face some instabilities, especially when the mass associated to the dummy point is large. To avoid them, increase the number of dummy points (allows a smoother repartition of the mass over the points).

Returns

  • partial_gw_dist (float) – partial GW discrepancy

  • log (dict) – log dictionary returned only if log is True

Examples

>>> import ot
>>> import scipy as sp
>>> a = np.array([0.25] * 4)
>>> b = np.array([0.25] * 4)
>>> x = np.array([1,2,100,200]).reshape((-1,1))
>>> y = np.array([3,2,98,199]).reshape((-1,1))
>>> C1 = sp.spatial.distance.cdist(x, x)
>>> C2 = sp.spatial.distance.cdist(y, y)
>>> np.round(partial_gromov_wasserstein2(C1, C2, a, b),2)
1.69
>>> np.round(partial_gromov_wasserstein2(C1, C2, a, b, m=0.25),2)
0.0

References

29

Chapel, L., Alaya, M., Gasso, G. (2020). “Partial Optimal Transport with Applications on Positive-Unlabeled Learning”. NeurIPS.

ot.partial.partial_wasserstein(a, b, M, m=None, nb_dummies=1, log=False, **kwargs)[source]

Solves the partial optimal transport problem for the quadratic cost and returns the OT plan

The function considers the following problem:

\[\gamma = \mathop{\arg \min}_\gamma \quad \langle \gamma, \mathbf{M} \rangle_F\]
\[ \begin{align}\begin{aligned}s.t. \ \gamma \mathbf{1} &\leq \mathbf{a}\\ \gamma^T \mathbf{1} &\leq \mathbf{b}\\ \gamma &\geq 0\\ \mathbf{1}^T \gamma^T \mathbf{1} = m &\leq \min\{\|\mathbf{a}\|_1, \|\mathbf{b}\|_1\}\end{aligned}\end{align} \]

where :

  • \(\mathbf{M}\) is the metric cost matrix

  • \(\mathbf{a}\) and \(\mathbf{b}\) are source and target unbalanced distributions

  • m is the amount of mass to be transported

Parameters
  • a (np.ndarray (dim_a,)) – Unnormalized histogram of dimension dim_a

  • b (np.ndarray (dim_b,)) – Unnormalized histograms of dimension dim_b

  • M (np.ndarray (dim_a, dim_b)) – cost matrix for the quadratic cost

  • m (float, optional) – amount of mass to be transported

  • nb_dummies (int, optional, default:1) – number of reservoir points to be added (to avoid numerical instabilities, increase its value if an error is raised)

  • log (bool, optional) – record log if True

  • **kwargs (dict) – parameters can be directly passed to the emd solver

Warning

When dealing with a large number of points, the EMD solver may face some instabilities, especially when the mass associated to the dummy point is large. To avoid them, increase the number of dummy points (allows a smoother repartition of the mass over the points).

Returns

  • gamma ((dim_a, dim_b) ndarray) – Optimal transportation matrix for the given parameters

  • log (dict) – log dictionary returned only if log is True

Examples

>>> import ot
>>> a = [.1, .2]
>>> b = [.1, .1]
>>> M = [[0., 1.], [2., 3.]]
>>> np.round(partial_wasserstein(a,b,M), 2)
array([[0.1, 0. ],
       [0. , 0.1]])
>>> np.round(partial_wasserstein(a,b,M,m=0.1), 2)
array([[0.1, 0. ],
       [0. , 0. ]])

References

28

Caffarelli, L. A., & McCann, R. J. (2010) Free boundaries in optimal transport and Monge-Ampere obstacle problems. Annals of mathematics, 673-730.

29

Chapel, L., Alaya, M., Gasso, G. (2020). “Partial Optimal Transport with Applications on Positive-Unlabeled Learning”. NeurIPS.

See also

ot.partial.partial_wasserstein_lagrange

Partial Wasserstein with

regularization

ot.partial.entropic_partial_wasserstein

Partial Wasserstein with a

entropic

Examples using ot.partial.partial_wasserstein

ot.partial.partial_wasserstein2(a, b, M, m=None, nb_dummies=1, log=False, **kwargs)[source]

Solves the partial optimal transport problem for the quadratic cost and returns the partial GW discrepancy

The function considers the following problem:

\[\gamma = \min_\gamma \quad \langle \gamma, \mathbf{M} \rangle_F\]
\[ \begin{align}\begin{aligned}s.t. \ \gamma \mathbf{1} &\leq \mathbf{a}\\ \gamma^T \mathbf{1} &\leq \mathbf{b}\\ \gamma &\geq 0\\ \mathbf{1}^T \gamma^T \mathbf{1} = m &\leq \min\{\|\mathbf{a}\|_1, \|\mathbf{b}\|_1\}\end{aligned}\end{align} \]

where :

  • \(\mathbf{M}\) is the metric cost matrix

  • \(\mathbf{a}\) and \(\mathbf{b}\) are source and target unbalanced distributions

  • m is the amount of mass to be transported

Parameters
  • a (np.ndarray (dim_a,)) – Unnormalized histogram of dimension dim_a

  • b (np.ndarray (dim_b,)) – Unnormalized histograms of dimension dim_b

  • M (np.ndarray (dim_a, dim_b)) – cost matrix for the quadratic cost

  • m (float, optional) – amount of mass to be transported

  • nb_dummies (int, optional, default:1) – number of reservoir points to be added (to avoid numerical instabilities, increase its value if an error is raised)

  • log (bool, optional) – record log if True

  • **kwargs (dict) – parameters can be directly passed to the emd solver

Warning

When dealing with a large number of points, the EMD solver may face some instabilities, especially when the mass associated to the dummy point is large. To avoid them, increase the number of dummy points (allows a smoother repartition of the mass over the points).

Returns

  • GW (float) – partial GW discrepancy

  • log (dict) – log dictionary returned only if log is True

Examples

>>> import ot
>>> a=[.1, .2]
>>> b=[.1, .1]
>>> M=[[0., 1.], [2., 3.]]
>>> np.round(partial_wasserstein2(a, b, M), 1)
0.3
>>> np.round(partial_wasserstein2(a,b,M,m=0.1), 1)
0.0

References

28

Caffarelli, L. A., & McCann, R. J. (2010) Free boundaries in optimal transport and Monge-Ampere obstacle problems. Annals of mathematics, 673-730.

29

Chapel, L., Alaya, M., Gasso, G. (2020). “Partial Optimal Transport with Applications on Positive-Unlabeled Learning”. NeurIPS.

ot.partial.partial_wasserstein_lagrange(a, b, M, reg_m=None, nb_dummies=1, log=False, **kwargs)[source]

Solves the partial optimal transport problem for the quadratic cost and returns the OT plan

The function considers the following problem:

\[\gamma = \mathop{\arg \min}_\gamma \quad \langle \gamma, (\mathbf{M} - \lambda) \rangle_F\]
\[ \begin{align}\begin{aligned}s.t. \ \gamma \mathbf{1} &\leq \mathbf{a}\\ \gamma^T \mathbf{1} &\leq \mathbf{b}\\ \gamma &\geq 0\\ \mathbf{1}^T \gamma^T \mathbf{1} = m & \leq \min\{\|\mathbf{a}\|_1, \|\mathbf{b}\|_1\}\end{aligned}\end{align} \]

or equivalently (see Chizat, L., Peyré, G., Schmitzer, B., & Vialard, F. X. (2018). An interpolating distance between optimal transport and Fisher–Rao metrics. Foundations of Computational Mathematics, 18(1), 1-44.)

\[ \begin{align}\begin{aligned}\gamma = \mathop{\arg \min}_\gamma \quad \langle \gamma, \mathbf{M} \rangle_F + \sqrt{\frac{\lambda}{2} (\|\gamma \mathbf{1} - \mathbf{a}\|_1 + \|\gamma^T \mathbf{1} - \mathbf{b}\|_1)}\\s.t. \ \gamma \geq 0\end{aligned}\end{align} \]

where :

  • \(\mathbf{M}\) is the metric cost matrix

  • \(\mathbf{a}\) and \(\mathbf{b}\) are source and target unbalanced distributions

  • \(\lambda\) is the lagrangian cost. Tuning its value allows attaining a given mass to be transported m

The formulation of the problem has been proposed in [28]

Parameters
  • a (np.ndarray (dim_a,)) – Unnormalized histogram of dimension dim_a

  • b (np.ndarray (dim_b,)) – Unnormalized histograms of dimension dim_b

  • M (np.ndarray (dim_a, dim_b)) – cost matrix for the quadratic cost

  • reg_m (float, optional) – Lagrangian cost

  • nb_dummies (int, optional, default:1) – number of reservoir points to be added (to avoid numerical instabilities, increase its value if an error is raised)

  • log (bool, optional) – record log if True

  • **kwargs (dict) – parameters can be directly passed to the emd solver

Warning

When dealing with a large number of points, the EMD solver may face some instabilities, especially when the mass associated to the dummy point is large. To avoid them, increase the number of dummy points (allows a smoother repartition of the mass over the points).

Returns

  • gamma ((dim_a, dim_b) ndarray) – Optimal transportation matrix for the given parameters

  • log (dict) – log dictionary returned only if log is True

Examples

>>> import ot
>>> a = [.1, .2]
>>> b = [.1, .1]
>>> M = [[0., 1.], [2., 3.]]
>>> np.round(partial_wasserstein_lagrange(a,b,M), 2)
array([[0.1, 0. ],
       [0. , 0.1]])
>>> np.round(partial_wasserstein_lagrange(a,b,M,reg_m=2), 2)
array([[0.1, 0. ],
       [0. , 0. ]])

References

28

Caffarelli, L. A., & McCann, R. J. (2010) Free boundaries in optimal transport and Monge-Ampere obstacle problems. Annals of mathematics, 673-730.

See also

ot.partial.partial_wasserstein

Partial Wasserstein with fixed mass