Assign value to boolvar based on other boolvars (CP-SAT | C#)

[Tyler Wallace]

Hey! I'm wondering if there is a more direct way to do the following: 

x, y, z are all boolvars. z is only true (1) if x & y are also true (1)

model.Add(z == 1).OnlyEnforceIf(new ILiteral[] { x, y });

model.Add(z == 0).OnlyEnforceIf(new ILiteral[] { x.Not(), y.Not() });

model.Add(z == 0).OnlyEnforceIf(new ILiteral[] { x.Not(), y });

model.Add(z == 0).OnlyEnforceIf(new ILiteral[] { x, y.Not() });

[Laurent Perron]

model.Add(z == 1).OnlyEnforceIf(new ILiteral[] { x, y });

->

model.AddBoolOr(new ILiteral[] {x.Not(), y.Not(), z }); ?

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--Laurent

[Tyler Wallace]

Thanks for the quick reply.

I admittedly do not understand the AddBoolOr and AddBoolAnd methods very well, so I've avoided them. I thought what you suggested was the equivalent of saying at least one of these has to be true, but all could be true: x == false OR y == false OR z == true. 

Anywhere I can read more about how it works or do you mind providing a quick explanation of AddBoolOr?

[Xiang Chen]

https://en.wikipedia.org/wiki/Material_implication_(rule_of_inference)

If you want

x and y <=> z

instead of just

x and y => z

you also have to add

z => x

z => y

using AddImplication

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[Tyler Wallace]

Ok. So if I have multiple boolvars that have to be true for another to be true, I can use implications. That sounds useful when I have more variables.

To expand it a bit, if I have v, w, x, y all have to be true for z to be true. (Is that written as: v and w and x and y <=> z ?) I can do:

model.Add(z == 1).OnlyEnforceIf(new ILiteral[] { v, w, x, y });

model.AddImplication(z, v);

model.AddImplication(z, w);

model.AddImplication(z, x);

model.AddImplication(z, y);

[blind.lin...@gmail.com]

On the topic of not understanding AddBoolOr...I didn't understand that
either so I wrote up a short blog post about it here:
https://activimetrics.com/blog/ortools/cp_sat/addboolor/. I wrote it
more as a note to my future self, but maybe it will help you too.

James

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> >> .
> >>
> >
> >
> > --
> > --Laurent

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James E. Marca
Activimetrics LLC

[Laurent Perron]

Nice blog entry.

Laurent Perron | Operations Research | lpe...@google.com | (33) 1 42 68 53 00

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