IDV in NoGoodsEngine

[tomosonalawa]

Hi @audemard,

I came accross an unexpected situation: I'm using the NoGoodsEngine with variable that have their domains defined as DomainValue.
In NoGoodsEngine::notifyNewDecision, I have added the following code:
auto valueId = x->valueId();
auto value = x->value();
auto other = x->domain.toIdv(value);
assert(valueId == other);

With the assumption that the value id should be the same regarding I retrieve it through the variable directly or through the domain.
However, this doesn´t appear to be the case as the assert is being triggered.

I've spotted this as in the code for 'NoGoodsEngine::notifiyDeleteDecision', the value id is obtained through the domain and not through the variable. Therefore, the positive decision for the value is not the same as the one that was added in the notifiyNewDecision.

Could you help me understand what I might be doing wrong?

Best regards,
Tomo

[audemard]

Hello,
With DomainValues, you have a mapping between indexes and values
For example : value s= {1, 5, 10, 100}
then
id=0 corresponds to values 1
id=1 corresponds to value 5 and so on.
So, there is a lot of chances that the assert is triggered.

x->domain.toIdv(v) get the id associated to a value of a variable.

If you add

• in NoGoodsEngine::notifyNewDecision
  std::cout << "Assign " << x->_name << "=" << x->valueId() << " " << x->value() << std::endl;

• NoGoodsEngine::notifyDeleteDecision
  std::cout << "Remove " << x->_name << " " << x->domain.toIdv(v) << " " << v << std::endl;

The trace gives the same couples id/value

I hope this can help you.

Best.
Gilles.

[tomosonalawa]

Thanks for the response,

I have the following trace:

[... a lot of assign, no remove ...]
Assign s46=0 0
Remove s46 40 0
cosoco/solver/nogoods/NoGoodsEngine.cc:223: virtual void Cosoco::NoGoodsEngine::notifyDeleteDecision(Cosoco::Variable*, int, Cosoco::Solver&): Assertion `pos >= 0' failed.

If I change the code of NoGoodsEngine::notifyNewDecision into
currentBranch.push(getPositiveDecisionFor(x, x->domain.toIdv(x->value())));

Then, the assert in notifyDeleteDecision (pos>=0) is not triggered (at least in my use-case).

Best regards,
Tomo

[audemard]

Very strange. I tried with domainValues and I have the following trace :

Assign x[2]=4 4
Remove x[2] 4 4

Gilles.

[tomosonalawa]

I've joined to this message a file with a reproducible test and a patch to be able to execute the test from the repo's main.
While running this test, I am seeing a case where the value's id is not the same when adding compared to when it is removed.

In the test, I have a custom constraint (X*n+Y=Z).

Let me know if you are not able to reproduce.

issue22.txt
test.cc.txt (Note that the extension was set to .txt to be accepted by github)

Best regards,
Tomo