Can anyone help me explain why the code are different results

Question

I have a code sample below , Can someone help me explain why the results are different

int : m=3; 
int : n=2; 
array[1..m,1..n] of int: va=[|1,2|
                              3,4|
                              5,6|];
array [1..m,1..n] of var int : val;
constraint forall(i in 1..m,j in 1..n )( i<2->val[i,j]=va[i,j]+1 );
constraint forall(i in 1..m,j in 1..n )( i>=2->val[i,j]=va[i,j]+3 );
output [ show(val) ];

int : m=3;
int : n=2; 
array[1..m,1..n] of int: va=[|1,2|
                              3,4|
                              5,6|];
array [1..m,1..n] of var int : val;

constraint forall(i in 1..m,j in 1..n )( i>=2->val[i,j]=va[i,j]+3 /\ i<2->val[i,j]=va[i,j]+1 );

output [ show(val) ];

if i can write this logic in one constraint?

Answer 1

In your second model the two implications (->) and the conjunction (/\) bind different then using two constraint sections.

The following give the same result as model 1. Note the parenthesis around the implications:

int : m=3;
int : n=2; 
array[1..m,1..n] of int: va=[|1,2|
                              3,4|
                              5,6|];
array [1..m,1..n] of var int : val;

constraint forall(i in 1..m,j in 1..n )( (i>=2->val[i,j]=va[i,j]+3) /\
                                         (i<2->val[i,j]=va[i,j]+1) );

output [ show(val) ];

Now both models outputs:

[2, 3, 6, 7, 8, 9]
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