Should I expect to have exactly same match everytime I run the match with greedy algorithm?

Question

I'm using greedy algorithm or local algorithm to match propensity score in two groups. I will end up with same number of matches every time but sometimes it doesn't match exactly same with last time. Is this normal?

Answer 1

"Greedy" doesn't necessarily mean "deterministic," in particular if you have two choices with equal weight/value then it may be possible to first select one choice during one algorithm execution and to first select the other choice on another algorithm execution.