Difficulty: Hard · Puzzle 2 of 6 · Topic: Distribution Puzzles (`dist`, `:=` vs `:/`)
Compute P(x==0) and P(x==7).
class dist_mix1;
rand int unsigned x;
constraint c {
x dist { [0:1] := 4, [2:9] :/ 4 };
}
endclassThe second range has 8 values, so :/ splits the total weight across 8.
1) Values 0,1 each get weight 4 from :=.
2) Values 2..9 each get weight 4/8=0.5 from :/.
3) Total weight = 2*4 + 8*0.5 = 12.
4) P(x==0)=4/12=1/3.
5) P(x==7)=0.5/12=1/24.Answer: P(x==0)=1/3 (~33.33%) and P(x==7)=1/24 (~4.17%).
Candidates often incorrectly give both ranges equal per-value probability because both clauses use weight 4.
If [2:9] changes to :=4, what does P(x==7) become?