COIN-OR backend for Sage MixedIntegerLinearProgram
sage-numerical-backends-coin: COIN-OR mixed integer linear programming backend for SageMath
CoinBackend has previously been available as part of the SageMath source tree,
from which it is built as an "optional extension" when then
cbc Sage package is installed.
However, it is not available in binary distributions such as:
- the Sage binary distribution (which does not package any optional packages),
- homebrew (which just uses the Sage binary distribution),
- Ubuntu (bionic 18.04LTS and several newer versions ship versions of SageMath, with various optional packages including CBC, but not the optional extension module CoinBackend),
- conda-forge (which ships SageMath and CBC but not the optional extension).
The present standalone Python package
sage-numerical-backends-coin has been created from the SageMath sources, version 9.0.beta10. It can be installed on top of various Sage installations using pip, including all of the above, including older versions of Sage such as 8.1 (as shipped by Ubuntu bionic 18.04LTS).
CBC can either be installed using its Sage package using
$ sage -i cbc
or any of the methods explained at https://github.com/coin-or/Cbc .
This package finds the CBC installation by means of
Install this package from PyPI using
$ sage -python -m pip install sage-numerical-backends-coin
or from GitHub using
$ sage -python -m pip install git+https://github.com/mkoeppe/sage-numerical-backends-coin
.github/workflows/build.yml for details about package prerequisites on various systems.)
Using this package
To obtain a solver (backend) instance:
sage: from sage_numerical_backends_coin.coin_backend import CoinBackend sage: CoinBackend() <sage_numerical_backends_coin.coin_backend.CoinBackend object at 0x7fb72c2c7528>
sage: from sage_numerical_backends_coin.coin_backend import CoinBackend sage: from sage.numerical.backends.generic_backend import get_solver sage: get_solver(solver=CoinBackend) <sage_numerical_backends_coin.coin_backend.CoinBackend object at 0x7fe21ffbe2b8>
To use this solver (backend) with
sage: from sage_numerical_backends_coin.coin_backend import CoinBackend sage: M = MixedIntegerLinearProgram(solver=CoinBackend) sage: M.get_backend() <sage_numerical_backends_coin.coin_backend.CoinBackend object at 0x7fb72c2c7868>
Setting it as the default backend for
MixedIntegerLinearProgram, as of SageMath 9.0.beta10, requires some trickery:
sage: import sage_numerical_backends_coin.coin_backend as coin_backend, sage.numerical.backends as backends, sys sage: sys.modules['sage.numerical.backends.coin_backend'] = backends.coin_backend = coin_backend sage: default_mip_solver('Coin')
To patch this in permanently (at your own risk):
$ sage -c 'import os; import sage.numerical.backends as dm; import sage_numerical_backends_coin.coin_backend as sm; s = sm.__file__; f = os.path.basename(s); d = os.path.join(dm.__path__, f); (os.path.exists(d) or os.path.lexists(d)) and os.remove(d); os.symlink(s, d);'
Or use the script
patch_into_sage_module.py in the source distribution that does the same:
$ sage -c 'load("patch_into_sage_module.py")' Success: Patched in the module as sage.numerical.backends.coin_backend
check_get_solver_with_name.py that the patching script has worked:
$ sage -c 'load("check_get_solver_with_name.py")' Success: get_solver(solver='coin') gives <sage_numerical_backends_coin.coin_backend.CoinBackend object at 0x7f8f20218528>
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