Here in the documentation of mosek (https://docs.mosek.com/latest/pythonfusion/debugging-numerical.html)

we see:

Never use a very large number as replacement for infinity . Instead define the variable or constraint as unbounded from below/above. Similarly, avoid artificial huge bounds if you expect they will not become tight in the optimal solution.

why is that the case?

I was recommended to look up a book in interior point method but unfortunately I don't have access. Could someone give me a high-level explanation why large bounds are can be bad for computational complexity?

  • $\begingroup$ I don't have an explanation, but the linked book can be found for free on Library Genesis $\endgroup$
    – whpowell96
    Commented Jan 31 at 16:45

1 Answer 1


It looks like MOSEK's founder has replied your question, it is pretty conclusive answer why they gave that suggestion in the MOSEK manual.

I can also tell you that if a bound is given as an actual infinity then you can do further simplifications and reduce the numerical error in the intermediate steps of the algorithm. If it is a very large number, then you cannot remove it and you have to do arithmetic with large numbers.

Doing arithmetic with numbers of different magnitudes on a computer is bad. For example $10^{17} - 1 = 10^{17}$, so you will not be able to compute some quantities accurately.


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