Does a lot of "if ... else" statements slow down the code?

[Wee_Beng_T_]

Hi,

I've a general question about F90. I've heard thatlots of "if ... else" statements slow down the code?

Especially with optimization and when one is trying to parallel the code.

Is this true? Or is this too general to define?

thanks!

[Steven_L_Intel1 · Accepted solution]

In general, yes, it would. Conditional statements pose difficulty for parallelization and vectorization, and a long series of IF-THEN can also cause instruction cache misses and other effects. But if that's what makes the code clearest, then use it.

This is not unique to Fortran - it would apply to any language.