Python framework for generating discrete structures
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README.md

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Haystack Diver

Haydi (Haystack diver) is a framework for generating discrete structures. It provides a way to define a structure from basic building blocks (e.g. Cartesian product, mappings) and then enumerate all elements, all non-isomorphic elements, or generate random elements.

Documentation

Full documentation is available at: https://haydi.readthedocs.io/en/latest/

Example of usage

  • Let us define directed graphs on two vertices (represented as a set of edges):
    >>> import haydi as hd
    >>> nodes = hd.USet(2, "n")  # A two-element set with (unlabeled) elements {n0, n1}
    >>> graphs = hd.Subsets(nodes * nodes)  # Subsets of a cartesian product
  • Now we can iterate all elements:
    >>> list(graphs.iterate())
    [{}, {(n0, n0)}, {(n0, n0), (n0, n1)}, {(n0, n0), (n0, n1), (n1, n0)}, {(n0,
    # ... 3 lines removed ...
    n1)}, {(n1, n0)}, {(n1, n0), (n1, n1)}, {(n1, n1)}]
  • or iterate all non-isomorphic ones:
    >>> list(graphs.cnfs())  # cnfs = canonical forms
    [{}, {(n0, n0)}, {(n0, n0), (n1, n1)}, {(n0, n0), (n0, n1)}, {(n0, n0), (n0,
    n1), (n1, n1)}, {(n0, n0), (n0, n1), (n1, n0)}, {(n0, n0), (n0, n1), (n1, n0),
    (n1, n1)}, {(n0, n0), (n1, n0)}, {(n0, n1)}, {(n0, n1), (n1, n0)}]
  • or generate random instances:
    >>> list(graphs.generate(3))
    [{(n1, n0)}, {(n1, n1), (n0, n0)}, {(n0, n1), (n1, n0)}]
  • Haydi supports standard operations like map, filter and reduce:
    >>> op = graphs.map(lambda g: len(g)).reduce(lambda x, y: x + y)
    # Just a demonstration pipeline; nothing usefull
    >>> op.run()
  • We can run it transparently as a distributed application:
    >>> from haydi import DistributedContext
    # We are now assuming that dask/distributed is running at hostname:1234
    >>> context = DistributedContext("hostname", 1234)
    >>> op.run(ctx=context)

Authors

  • Stanislav Böhm <stanislav.bohm at vsb.cz>
  • Jakub Beránek
  • Martin Šurkovský <martin.surkovsky at gmail.com>