1 unit xyz_u {
2
3 field_A: uint;
4 keep soft field_A in [1..4];
5
6 field_B: uint;
7 // ************* COMMENTS ***********************
8 // I wanted here fieldB to have 1 when fieldA =1;
9 // fieldB = fieldA/2 if fieldA != 1
10 // you know what, it yielded me results
11 // when filed_A = 4 it gave me field_B = 1
12 // that is becuase when field_A !=1,
13 // this could be becuase the constraining can
14 // happen both the ways RHS to LHS and vice-versa
15 // and also specman never assures that it will
16 // satisfy both the below conditions. Specman
17 // only **tries** to generate the value which
18 // satisfy below equations.
19 // It may not satisfy always.
20 keep field_A == 1 => field_B == 1;
21 // since this is implied constr. you can't use 'soft'
22 keep filed_A != 1 => field_B == field_A/2;
23 // this is very very dangerous
24 };
25
* what is the Real problem?
Specman doesn't give any hint or information as how it has generated and what conditions(equations) are really satisfied. It keeps the user in *dark* and doesnt really help the user to debug in anyway.
* what is the way out?
1. Look out for ways to avoid the conditional constraints.
2. Try to avoid negative way of implied constraining ( !=), it opens up the space for specman to play with the conditions.
3. Suppose if you can't get rid of the implied constraints. Try to break it up( I am not sure whether it works out well!!!)
