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eomahony / Numberjack

Python Combinatorial Optimisation Platform
http://numberjack.ucc.ie
GNU Lesser General Public License v2.1
157 stars 36 forks source link

solver.getNextSolution vs solver.solutions #29

Closed braingineer closed 8 years ago

braingineer commented 8 years ago

Hello!

I am trying to use Numberjack to solve a CSP problem.

I have the model built and I am trying two different ways of solving (as illustrated in your examples). All of my variables are binary.

Method1: solver = model.load("Mistral") solver.solve() while solver.solutions():

reference variables to get solutions

 solutions = [val for sym,val in sym_dict.items() if sym.get_value()!=0]

Method2 solver = model.load("Mistral") solver.startNewSearch() while solver.getNextSolution() == Numberjack.SAT:

reference variables to get solutions

 solutions = [val for sym,val in sym_dict.items() if sym.get_value()!=0]

The second method will terminate immediately for me. The first method works. Why is this?

All the best, Brian

ehebrard commented 8 years ago

Can you please send us a full example? I do not observe the same behavior.

And (Barry, please correct me if I'm wrong) the first method should be something like: for _ in solver.solutions():

On Thu, Dec 17, 2015 at 8:51 PM, Brian McMahan notifications@github.com wrote:

Hello!

I am trying to use Numberjack to solve a CSP problem.

I have the model built and I am trying two different ways of solving (as illustrated in your examples). All of my variables are binary.

Method1: solver = model.load("Mistral") solver.solve() while solver.solutions():

reference variables to get solutions

solutions = [val for sym,val in sym_dict.items() if sym.get_value()!=0]

Method2 solver = model.load("Mistral") solver.startNewSearch() while solver.getNextSolution() == Numberjack.SAT:

reference variables to get solutions

solutions = [val for sym,val in sym_dict.items() if sym.get_value()!=0]

The second method will terminate immediately for me. The first method works. Why is this?

All the best, Brian

— Reply to this email directly or view it on GitHub https://github.com/eomahony/Numberjack/issues/29.

-Emmanuel

braingineer commented 8 years ago

Hi!

Thanks for the response.

You are correct on the for loop. Not fully sure what I was thinking there.

I'm trying to recreate with what I thought was the reason the issue was happening, but other small bugs are now presenting themselves. I'll ping back either when I have a minimum working example or determine that I've made a mistake in this question =)

Best, Brian

braingineer commented 8 years ago

Hi, I think that this was my mistake in how I formulated the code. Things are working now as expected (modulo a loophole in the constraints I've set up). Thanks again.