alt Hacker NewsUsing a bad algorithm when a good algorithm that is known to exist is premature pessimization and should be avoided.
There is some debate about what premature optimization is, but I consider it about micro optimizations that often are doing things a modern compiler will do for you better than you can. All too often such attempts result in unreadable code that is slower because the optimizer would have done something different but now it cannot. Premature optimization is done without a profiler - if you have a profile of your code and can show a change really makes a difference then it isn't premature.
On the other hand job interviews imply time pressure. If someone isn't 100% sure how to implement the optimization algorithm without looking it up brute force is faster and should be chosen then. In the real world if I'm asked to do something I can spend days researching algorithms at times (though the vast majority of the time what I need is already in my language's standard library)
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IBO premature optimization is normally one of two things:
1. Any optimization in a typical web development file where the process is not expected to be particularly complex. Usually a good developer will not write something very inefficient and usually bottlenecks come from other areas
2. Doing stuff like replacing a forEach with a for loop to be 0.5% faster
Constraint solvers (or MILP solvers) while not asymptotically optimal are often as fast or faster than other methods.
> when a good algorithm that is known to exist
Sure, if a good algorithm exists and is simple to implement, then go for it. But if it is non-trivial, then you have to make a judgement call whether it is worth the trouble to solve in a more optimal way. You acknowledge yourself that that this can take days.
Personally I really have to be disciplined about choosing what to optimize vs what to code up quick-and-dirty. There's always a temptation to write clean, custom solutions because that's more interesting, but it's just not a good use of time for non-performance critical code.