# ModularityState#

class graph_tool.inference.ModularityState(g, b=None, eweight=None, entropy_args={})[source]#

Obtain the partition of a network according to the maximization of Newman’s modularity.

Danger

Using modularity maximization is almost always a terrible idea.

Modularity maximization is a substantially inferior method to the inference-based ones that are implemented in graph-tool, since it does not possess any kind of statistical regularization. Among many other problems, the method tends to massively overfit empirical data.

For a more detailed explanation see “Modularity maximization considered harmful”, as well as [peixoto-descriptive-2023].

Do not use this approach in the analysis of networks without understanding the consequences. This algorithm is included only for comparison purposes. In general, the inference-based approaches based on BlockState, NestedBlockState, and PPBlockState should be universally preferred.

Parameters:
gGraph

Graph to be partitioned.

bPropertyMap (optional, default: None)

Initial partition. If not supplied, a partition into a single group will be used.

eweightEdgePropertyMap (optional, default: None)

Edge multiplicities (for multigraphs).

entropy_args: dict (optional, default: {})

Override default arguments for entropy() method and releated operations.

Methods

 copy([g, b]) Copies the state. draw(**kwargs) Convenience wrapper to graph_draw() that draws the state of the graph as colors on the vertices and edges. entropy([gamma]) Return the unnormalized negative generalized modularity. Returns the total number of blocks. Returns the effective number of blocks, defined as $$e^{H}$$, with $$H=-\sum_r\frac{n_r}{N}\ln \frac{n_r}{N}$$, where $$n_r$$ is the number of nodes in group r. Return the current default values for the parameters of the function entropy(), together with other operations that depend on them. gibbs_sweep([beta, niter, entropy_args, ...]) Perform niter sweeps of a rejection-free Gibbs MCMC to sample network partitions. mcmc_sweep([beta, c, d, niter, ...]) Perform niter sweeps of a Metropolis-Hastings acceptance-rejection MCMC to sample network partitions. modularity([gamma]) Return the generalized modularity. multiflip_mcmc_sweep([beta, c, psingle, ...]) Perform niter sweeps of a Metropolis-Hastings acceptance-rejection MCMC with multiple simultaneous moves (i.e. merges and splits) to sample network partitions. multilevel_mcmc_sweep([niter, beta, c, d, ...]) Perform niter sweeps of a multilevel agglomerative acceptance-rejection pseudo-MCMC (i.e. detailed balance is not preserved) to sample network partitions, that uses a bisection search on the number of groups, together with group merges and singe-node moves. Reset the current default values for the parameters of the function entropy(), together with other operations that depend on them. update_entropy_args(**kwargs) Update the default values for the parameters of the function entropy() from the keyword arguments, in a stateful way, together with other operations that depend on them.
copy(g=None, b=None)[source]#

Copies the state. The parameters override the state properties, and have the same meaning as in the constructor.

draw(**kwargs)#

Convenience wrapper to graph_draw() that draws the state of the graph as colors on the vertices and edges.

entropy(gamma=1.0)#

Return the unnormalized negative generalized modularity.

Warning

The default arguments of this function are overriden by those obtained from get_entropy_args(). To update the defaults in a stateful way, update_entropy_args() should be called.

Notes

The unnormalized negative generalized modularity is defined as

$-\sum_{ij}\left(A_{ij}-\gamma \frac{k_ik_j}{2E}\right)$

Where $$A_{ij}$$ is the adjacency matrix, $$k_i$$ is the degree of node $$i$$, and $$E$$ is the total number of edges.

get_B()[source]#

Returns the total number of blocks.

get_Be()[source]#

Returns the effective number of blocks, defined as $$e^{H}$$, with $$H=-\sum_r\frac{n_r}{N}\ln \frac{n_r}{N}$$, where $$n_r$$ is the number of nodes in group r.

get_entropy_args()#

Return the current default values for the parameters of the function entropy(), together with other operations that depend on them.

gibbs_sweep(beta=1.0, niter=1, entropy_args={}, allow_new_group=True, sequential=True, deterministic=False, vertices=None, verbose=False, **kwargs)#

Perform niter sweeps of a rejection-free Gibbs MCMC to sample network partitions.

Parameters:
betafloat (optional, default: 1.)

Inverse temperature.

niterint (optional, default: 1)

Number of sweeps to perform. During each sweep, a move attempt is made for each node.

entropy_argsdict (optional, default: {})

Entropy arguments, with the same meaning and defaults as in graph_tool.inference.BlockState.entropy().

allow_new_groupbool (optional, default: True)

Allow the number of groups to increase and decrease.

sequentialbool (optional, default: True)

If sequential == True each vertex move attempt is made sequentially, where vertices are visited in random order. Otherwise the moves are attempted by sampling vertices randomly, so that the same vertex can be moved more than once, before other vertices had the chance to move.

deterministicbool (optional, default: False)

If sequential == True and deterministic == True the vertices will be visited in deterministic order.

verticeslist of ints (optional, default: None)

If provided, this should be a list of vertices which will be moved. Otherwise, all vertices will.

verbosebool (optional, default: False)

If verbose == True, detailed information will be displayed.

Returns:
dSfloat

Entropy difference after the sweeps.

nattemptsint

Number of vertex moves attempted.

nmovesint

Number of vertices moved.

Notes

This algorithm has an $$O(E\times B)$$ complexity, where $$B$$ is the number of groups, and $$E$$ is the number of edges.

mcmc_sweep(beta=1.0, c=0.5, d=0.01, niter=1, entropy_args={}, allow_vacate=True, sequential=True, deterministic=False, vertices=None, verbose=False, **kwargs)#

Perform niter sweeps of a Metropolis-Hastings acceptance-rejection MCMC to sample network partitions.

Parameters:
betafloat (optional, default: 1.)

Inverse temperature.

cfloat (optional, default: .5)

Sampling parameter c for move proposals: For $$c\to 0$$ the blocks are sampled according to the local neighborhood of a given node and their block connections; for $$c\to\infty$$ the blocks are sampled randomly. Note that only for $$c > 0$$ the MCMC is guaranteed to be ergodic.

dfloat (optional, default: .01)

Probability of selecting a new (i.e. empty) group for a given move.

niterint (optional, default: 1)

Number of sweeps to perform. During each sweep, a move attempt is made for each node.

entropy_argsdict (optional, default: {})

Entropy arguments, with the same meaning and defaults as in graph_tool.inference.BlockState.entropy().

allow_vacatebool (optional, default: True)

Allow groups to be vacated.

sequentialbool (optional, default: True)

If sequential == True each vertex move attempt is made sequentially, where vertices are visited in random order. Otherwise the moves are attempted by sampling vertices randomly, so that the same vertex can be moved more than once, before other vertices had the chance to move.

deterministicbool (optional, default: False)

If sequential == True and deterministic == True the vertices will be visited in deterministic order.

verticeslist of ints (optional, default: None)

If provided, this should be a list of vertices which will be moved. Otherwise, all vertices will.

verbosebool (optional, default: False)

If verbose == True, detailed information will be displayed.

Returns:
dSfloat

Entropy difference after the sweeps.

nattemptsint

Number of vertex moves attempted.

nmovesint

Number of vertices moved.

Notes

This algorithm has an $$O(E)$$ complexity, where $$E$$ is the number of edges (independent of the number of groups).

References

[peixoto-efficient-2014]

Tiago P. Peixoto, “Efficient Monte Carlo and greedy heuristic for the inference of stochastic block models”, Phys. Rev. E 89, 012804 (2014), DOI: 10.1103/PhysRevE.89.012804 [sci-hub, @tor], arXiv: 1310.4378

modularity(gamma=1)[source]#

Return the generalized modularity.

Notes

The generalized modularity is defined as

$\frac{1}{2E}\sum_{ij}\left(A_{ij}-\gamma \frac{k_ik_j}{2E}\right)$

Where $$A_{ij}$$ is the adjacency matrix, $$k_i$$ is the degree of node $$i$$, and $$E$$ is the total number of edges.

multiflip_mcmc_sweep(beta=1.0, c=0.5, psingle=None, psplit=1, pmerge=1, pmergesplit=1, pmovelabel=0, d=0.01, gibbs_sweeps=10, niter=1, entropy_args={}, accept_stats=None, verbose=False, **kwargs)#

Perform niter sweeps of a Metropolis-Hastings acceptance-rejection MCMC with multiple simultaneous moves (i.e. merges and splits) to sample network partitions.

Parameters:
betafloat (optional, default: 1.)

Inverse temperature.

cfloat (optional, default: .5)

Sampling parameter c for move proposals: For $$c\to 0$$ the blocks are sampled according to the local neighborhood of a given node and their block connections; for $$c\to\infty$$ the blocks are sampled randomly. Note that only for $$c > 0$$ the MCMC is guaranteed to be ergodic.

psinglefloat (optional, default: None)

Relative probability of proposing a single node move. If None, it will be selected as the number of nodes in the graph.

psplitfloat (optional, default: 1)

Relative probability of proposing a group split.

pmergesplitfloat (optional, default: 1)

Relative probability of proposing a marge-split move.

pmovelabelfloat (optional, default: 0)

Relative probability of proposing a group label move.

dfloat (optional, default: 1)

Probability of selecting a new (i.e. empty) group for a given single-node move.

gibbs_sweepsint (optional, default: 10)

Number of sweeps of Gibbs sampling to be performed (i.e. each node is attempted once per sweep) to refine a split proposal.

niterint (optional, default: 1)

Number of sweeps to perform. During each sweep, a move attempt is made for each node, on average.

entropy_argsdict (optional, default: {})

Entropy arguments, with the same meaning and defaults as in graph_tool.inference.BlockState.entropy().

verbosebool (optional, default: False)

If verbose == True, detailed information will be displayed.

Returns:
dSfloat

Entropy difference after the sweeps.

nattemptsint

Number of vertex moves attempted.

nmovesint

Number of vertices moved.

Notes

This algorithm has an $$O(E)$$ complexity, where $$E$$ is the number of edges (independent of the number of groups).

References

[peixoto-merge-split-2020]

Tiago P. Peixoto, “Merge-split Markov chain Monte Carlo for community detection”, Phys. Rev. E 102, 012305 (2020), DOI: 10.1103/PhysRevE.102.012305 [sci-hub, @tor], arXiv: 2003.07070

multilevel_mcmc_sweep(niter=1, beta=inf, c=0.5, d=0.01, r=0.9, random_bisect=True, merge_sweeps=10, mh_sweeps=10, init_r=0.99, init_min_iter=5, init_beta=1.0, gibbs=False, B_min=1, B_max=18446744073709551615, b_min=None, b_max=None, M=None, cache_states=True, force_accept=False, parallel=False, entropy_args={}, verbose=False, **kwargs)#

Perform niter sweeps of a multilevel agglomerative acceptance-rejection pseudo-MCMC (i.e. detailed balance is not preserved) to sample network partitions, that uses a bisection search on the number of groups, together with group merges and singe-node moves.

Parameters:
niterint (optional, default: 1)

Number of sweeps to perform. During each sweep, a move attempt is made for each node, on average.

betafloat (optional, default: numpy.inf)

Inverse temperature.

cfloat (optional, default: .5)

Sampling parameter c for move proposals: For $$c\to 0$$ the blocks are sampled according to the local neighborhood of a given node and their block connections; for $$c\to\infty$$ the blocks are sampled randomly. Note that only for $$c > 0$$ the MCMC is guaranteed to be ergodic.

dfloat (optional, default: .01)

Probability of selecting a new (i.e. empty) group for a given single-node move.

rfloat (optional, default: 0.9)

Group shrink ratio. The number of groups is reduced by this fraction at each merge sweep.

random_bisectbool (optional, default: True)

If True, bisections are done at randomly chosen intervals. Otherwise a Fibonacci sequence is used.

merge_sweepsint (optional, default: 10)

Number of sweeps spent to find good merge proposals.

mh_sweepsint (optional, default: 10)

Number of single-node Metropolis-Hastings sweeps between merge splits.

init_rdouble (optional, default: 0.99)

Stopping criterion for the intialization phase, after each node is put in their own group, to set the initial upper bound of the bisection search. A number of single-node Metropolis-Hastings sweeps is done until the number of groups is shrunk by a factor that is larger than this parameter.

init_min_iterint (optional, default: 5)

Minimum number of iterations at the intialization phase.

init_betafloat (optional, default: 1.)

Inverse temperature to be used for the very first sweep of the initialization phase.

gibbsbool (optional, default: False)

If True, the single node moves use (slower) Gibbs sampling, rather than Metropolis-Hastings.

B_minint (optional, default: 1)

Minimum number of groups to be considered in the search.

b_minVertexPropertyMap (optional, default: None)

If provided, this will be used for the partition corresponding to B_min.

B_maxint (optional, default: 1)

Maximum number of groups to be considered in the search.

b_maxVertexPropertyMap (optional, default: None)

If provided, this will be used for the partition corresponding to B_max.

Mint (optional, default: None)

Maximum number of groups to select for the multilevel move. If None is provided, then all groups are always elected.

cache_statesbool (optional, default: True)

If True, intermediary states will be cached during the bisection search.

force_acceptbool (optional, default: False)

If True, new state will be accepted even if it does not improve the objective function.

parallelbool (optional, default: False)

If True, the algorithm will run in parallel (if enabled during compilation).

entropy_argsdict (optional, default: {})

Entropy arguments, with the same meaning and defaults as in graph_tool.inference.BlockState.entropy().

verbosebool (optional, default: False)

If verbose == True, detailed information will be displayed.

Returns:
dSfloat

Entropy difference after the sweeps.

nattemptsint

Number of vertex moves attempted.

nmovesint

Number of vertices moved.

Notes

This algorithm has an $$O(E\ln^2 N)$$ complexity, where $$E$$ is the number of edges and $$N$$ is the number of nodes (independently of the number of groups).

References

[peixoto-efficient-2014]

Tiago P. Peixoto, “Efficient Monte Carlo and greedy heuristic for the inference of stochastic block models”, Phys. Rev. E 89, 012804 (2014), DOI: 10.1103/PhysRevE.89.012804 [sci-hub, @tor], arXiv: 1310.4378

reset_entropy_args()#

Reset the current default values for the parameters of the function entropy(), together with other operations that depend on them.

update_entropy_args(**kwargs)#

Update the default values for the parameters of the function entropy() from the keyword arguments, in a stateful way, together with other operations that depend on them.

Values updated in this manner are preserved by the copying or pickling of the state.