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Add configuration model #796

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@tapanih tapanih commented Jan 28, 2023

Added a possibility to generate a random graph using a configuration model. The result is a random graph with a given degree sequence. The Rust library can additionally generate degree sequences from any Distribution.

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Pull Request Test Coverage Report for Build 4032314256

  • 91 of 122 (74.59%) changed or added relevant lines in 3 files are covered.
  • 4 unchanged lines in 2 files lost coverage.
  • Overall coverage decreased (-0.2%) to 96.802%

Changes Missing Coverage Covered Lines Changed/Added Lines %
rustworkx-core/src/generators/configuration_model.rs 56 87 64.37%
Files with Coverage Reduction New Missed Lines %
src/shortest_path/all_pairs_bellman_ford.rs 2 98.88%
src/shortest_path/all_pairs_dijkstra.rs 2 98.54%
Totals Coverage Status
Change from base Build 4028447013: -0.2%
Covered Lines: 13835
Relevant Lines: 14292

💛 - Coveralls

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@IvanIsCoding IvanIsCoding left a comment

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Thanks for contributing this! This is neat.

I will have to read the paper to give a better review of the code, but I do have a question about graph realization right off the bat

Some(seed) => Pcg64::seed_from_u64(seed),
None => Pcg64::from_entropy(),
};
let degree_sequence = match core_generators::DegreeSequence::new(degree_sequence) {
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Do you need to check this degree sequence with Erdős–Gallai? Or do you return a graph that might not be a simple graph?

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@tapanih tapanih Jan 30, 2023

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The graph may not be simple. The generator in NetworkX works in a similar fashion: https://networkx.org/documentation/stable/reference/generated/networkx.generators.degree_seq.configuration_model.html#configuration-model

At some point, it would be good to add a parameter to DegreeSequence constructors that specifies that the degree sequence must be graphical.

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IvanIsCoding commented Jan 29, 2023

Also, you'll have to update api.rst to include the new function you added

}
if sum % 2 == 1 {
let index = rng.gen_range(0..length);
degree_sequence[index] += 1;
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@tapanih tapanih Jan 30, 2023

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This felt like a "pragmatic" way of ensuring that the sum is even. However, this could lead to out-of-distribution values in the sequence which is probably confusing for the user. Not sure how to fix it. Probably just retry n times?

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5 participants