CPLEX MIP warm start seems slow down the program?

Question

I have been working on a combinatorial optimization problem which can be modeled as an integer linear programming. I implemented it as a c++ project in visual studio 2017 and CPLEX1271. With the hope that my program would run faster, I use MIPStart to provide cplex a feasible solution. But the running time changed from 49s to 140s. All I did is providing a feasible solution to cplex, according to the answer, it cannot hurt the running time. Can anyone explain it?
UPDATE1: The log shows that cplex accept the solution.
UPDATE2: I've tested on hundreds of instances. It turned out that a warm start sometimes slows down cplex and at other times it accelerates cplex.

Nikos Kazazakis · Answer

If the solution you provided is not very good (i.e., it's far from the global optimum), it often leads the branch-and-bound algorithm down a different path, which ends up slowing down the overall solution time.
MIP solvers are very good in figuring this stuff out by themselves, so the best use of warm-start nowadays is when we solve many similar problems sequentially.

CPLEX MIP warm start seems slow down the program?

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