Model info/remove constraints

Eric

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Feb 15, 2016, 12:31:11 PM2/15/16

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Hi,

I am working with c++ API (not the command line flags) using the latest version of CP solver in windows. I have a few questions regarding my effort to use or-tools as follows:
1. How can I get some statistics (number of variables, constraints, ...) on the model itself? The only thing that I have found is Constraints() method from the solver class to retrieve the number of constraints in the model.
2. How can I export the model in a readable format just for debug purpose not re-use it again?
3. How can I remove a variable or constraint from the model?

Thank you so much.

Eric

Laurent Perron

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Feb 15, 2016, 2:36:49 PM2/15/16

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Hi

There are a few visitors on the model

Take one C++ example (golomb for example)

/bin/golomb --cp_model_stats --size=6 --log_prefix=false

Model has:

- 11 constraints.

* 1 AllDifferent

* 10 CastExpressionIntoVariable

- 16 integer variables.

- 10 integer expressions.

* 10 Difference

- 10 expressions casted into variables.

- 0 interval variables.

- 0 sequence variables.

- 2 model extensions.

* 1 VariableGroup

* 1 Objective

N = 6, optimal length = 17 (fails:8)

and

./bin/golomb --cp_print_model --size=6 --log_prefix=false

Model golomb {

CastExpressionIntoVariable

expression: Difference

left: X02(1..217)

right: X01(1..217)

target_variable: Difference

left: X02(1..217)

right: X01(1..217)

CastExpressionIntoVariable

expression: Difference

left: X03(1..217)

right: X01(1..217)

target_variable: Difference

left: X03(1..217)

right: X01(1..217)

CastExpressionIntoVariable

expression: Difference

left: X04(1..217)

right: X01(1..217)

target_variable: Difference

left: X04(1..217)

right: X01(1..217)

CastExpressionIntoVariable

expression: Difference

left: X05(1..217)

right: X01(1..217)

target_variable: Difference

left: X05(1..217)

right: X01(1..217)

CastExpressionIntoVariable

expression: Difference

left: X03(1..217)

right: X02(1..217)

target_variable: Difference

left: X03(1..217)

right: X02(1..217)

CastExpressionIntoVariable

expression: Difference

left: X04(1..217)

right: X02(1..217)

target_variable: Difference

left: X04(1..217)

right: X02(1..217)

CastExpressionIntoVariable

expression: Difference

left: X05(1..217)

right: X02(1..217)

target_variable: Difference

left: X05(1..217)

right: X02(1..217)

CastExpressionIntoVariable

expression: Difference

left: X04(1..217)

right: X03(1..217)

target_variable: Difference

left: X04(1..217)

right: X03(1..217)

CastExpressionIntoVariable

expression: Difference

left: X05(1..217)

right: X03(1..217)

target_variable: Difference

left: X05(1..217)

right: X03(1..217)

CastExpressionIntoVariable

expression: Difference

left: X05(1..217)

right: X04(1..217)

target_variable: Difference

left: X05(1..217)

right: X04(1..217)

AllDifferent

variables: [

X01(1..217)

X02(1..217)

X03(1..217)

X04(1..217)

X05(1..217)

Difference

left: X02(1..217)

right: X01(1..217)

Difference

left: X03(1..217)

right: X01(1..217)

Difference

left: X04(1..217)

right: X01(1..217)

Difference

left: X05(1..217)

right: X01(1..217)

Difference

left: X03(1..217)

right: X02(1..217)

Difference

left: X04(1..217)

right: X02(1..217)

Difference

left: X05(1..217)

right: X02(1..217)

Difference

left: X04(1..217)

right: X03(1..217)

Difference

left: X05(1..217)

right: X03(1..217)

Difference

left: X05(1..217)

right: X04(1..217)

]

range: 1

Objective

maximize: 0

step: 1

expression: X05(1..217)

VariableGroup

variables: [

IntConst(0)

X01(1..217)

X02(1..217)

X03(1..217)

X04(1..217)

X05(1..217)

]

}

N = 6, optimal length = 17 (fails:8)

You check the code behind these flags (src/constraint_solver/constraint_solver.cc).

You create the relevant visitor, and then run solver.Accept(visitor) after the model is created.

You can also see

./bin/golomb --cp_print_added_constraints --size=6 --log_prefix=false

cast((X02(1..217) - X01(1..217)), CastVar<0>(-216..216))

cast((X03(1..217) - X01(1..217)), CastVar<1>(-216..216))

cast((X04(1..217) - X01(1..217)), CastVar<2>(-216..216))

cast((X05(1..217) - X01(1..217)), CastVar<3>(-216..216))

cast((X03(1..217) - X02(1..217)), CastVar<4>(-216..216))

cast((X04(1..217) - X02(1..217)), CastVar<5>(-216..216))

cast((X05(1..217) - X02(1..217)), CastVar<6>(-216..216))

cast((X04(1..217) - X03(1..217)), CastVar<7>(-216..216))

cast((X05(1..217) - X03(1..217)), CastVar<8>(-216..216))

cast((X05(1..217) - X04(1..217)), CastVar<9>(-216..216))

BoundsAllDifferent(X01(1..217), X02(1..217), X03(1..217), X04(1..217), X05(1..217), CastVar<0>(1..216), CastVar<1>(1..216), CastVar<2>(1..216), CastVar<3>(1..216), CastVar<4>(1..216), CastVar<5>(1..216), CastVar<6>(1..216), CastVar<7>(1..216), CastVar<8>(1..216), CastVar<9>(1..216))

N = 6, optimal length = 17 (fails:8)

which is often more useful with the --cp_name_cast_variables

./bin/golomb --cp_print_added_constraints --size=6 --log_prefix=false --cp_name_cast_variables

cast((X02(1..217) - X01(1..217)), Var<(X02(1..217) - X01(1..217))>(-216..216))

cast((X03(1..217) - X01(1..217)), Var<(X03(1..217) - X01(1..217))>(-216..216))

cast((X04(1..217) - X01(1..217)), Var<(X04(1..217) - X01(1..217))>(-216..216))

cast((X05(1..217) - X01(1..217)), Var<(X05(1..217) - X01(1..217))>(-216..216))

cast((X03(1..217) - X02(1..217)), Var<(X03(1..217) - X02(1..217))>(-216..216))

cast((X04(1..217) - X02(1..217)), Var<(X04(1..217) - X02(1..217))>(-216..216))

cast((X05(1..217) - X02(1..217)), Var<(X05(1..217) - X02(1..217))>(-216..216))

cast((X04(1..217) - X03(1..217)), Var<(X04(1..217) - X03(1..217))>(-216..216))

cast((X05(1..217) - X03(1..217)), Var<(X05(1..217) - X03(1..217))>(-216..216))

cast((X05(1..217) - X04(1..217)), Var<(X05(1..217) - X04(1..217))>(-216..216))

BoundsAllDifferent(X01(1..217), X02(1..217), X03(1..217), X04(1..217), X05(1..217), Var<(X02(1..217) - X01(1..217))>(1..216), Var<(X03(1..217) - X01(1..217))>(1..216), Var<(X04(1..217) - X01(1..217))>(1..216), Var<(X05(1..217) - X01(1..217))>(1..216), Var<(X03(1..217) - X02(1..217))>(1..216), Var<(X04(1..217) - X02(1..217))>(1..216), Var<(X05(1..217) - X02(1..217))>(1..216), Var<(X04(1..217) - X03(1..217))>(1..216), Var<(X05(1..217) - X03(1..217))>(1..216), Var<(X05(1..217) - X04(1..217))>(1..216))

N = 6, optimal length = 17 (fails:8)

All these flags are also available as parameters to the solver (see src/constraint_solver/solver_parameters.proto

I hope this helps.

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Eric

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Feb 16, 2016, 3:26:37 AM2/16/16

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Thanks Laurent for your prompt answer.

I have got how to get the model stats, but I am still do not know how to remove a variable or constraint from the model?

Cheers,
Eric

louis Ucheya

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Mar 2, 2016, 4:25:24 PM3/2/16

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Hi Eric,

Did you ever figure out how to remove a variable or constraint the model?

Thanks,

Louis

Eric

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Mar 2, 2016, 5:35:45 PM3/2/16

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Hi Louis,

No. I haven't got any reply back so far regrading removing a variable or constraint.

Thanks,
Eric

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