I am building a bidding VRP model using constraint programming with DOCPLEX. In this model, I have the following constraint:

IF {presentOf(xtime[k]) == 0}, THEN {sum(b in B)z[k][b] == 0 – forall k in KN}

and

IF {sum(b in B)z[k][b] == 0} – forall k in KN, THEN {presentOf(xtime[k]) == 0}

This is my code

for k in KN:
    model.add(model.if_then(sum(z[k -NberExistConstract- 1][b-1] for b in B) == 0, model.presence_of(xtime[k-NberExistConstract-1])==0))
    model.add(model.if_then(model.presence_of(xtime[k-NberExistConstract-1])==0, sum(z[k -NberExistConstract- 1][b-1] for b in B) == 0))

I have tried using if_then as shown in the link, but it is not effective; the results are incorrect. For example wrong solution:

xtime_19: absent
but: z_19_1 = 1; z_19_2 = 0; z_19_3 = 0 and sum(z_19_1; z_19_2; z_19_3) = 1.

It should be:

xtime_19: absent
but: z_19_1 = 0; z_19_2 = 0; z_19_3 = 0 and sum(z_19_1; z_19_2; z_19_3) = 0.

This is full code: https://drive.google.com/drive/folders/1-Fnk0QkBV5_PF1EsPNA6VZSz4XDd37Ir?usp=drive_link

Please help me, thanks

I have try this example

1/ https://github.com/AlexFleischerParis/zoodocplex/blob/master/zooifthen.py

2/ https://github.com/AlexFleischerParis/zoodocplex/blob/master/zooifthen2.py

3/ https://github.com/AlexFleischerParis/zoodocplex/blob/master/zooifthenwithstaticcondition.py

But it does not works and still give the wrong solution