"Luca Béla Palkovics" <luca.bela.palkovics@xxxxxxxxx> writes: > Is this normal ? b has nothing todo with a .. why does a get slower ? > (b is also faster without a...) There are a number of possibilities. It's hard to know what is happening without an exact test case. You also neglected to say what platform you are running on. Some possibilities are: 1) Measurement error. Surprisingly often people are not measuring what they think they are measuring, and you didn't provide any details about how you got your timings. 2) Instruction cache effects, if a() and b() call other functions. When both are linked together, those other functions will be at different addresses, and whether they are contiguous may change, all affecting the instruction cache. 3) Exact aligment of loop starts may shift when both are linked together, affecting the processor's branch optimizers if it has any. Similarly, the exact alignment of labels may shift. You can control these using gcc options like -falign-functions, -falign-jumps, -falign-labels, -falign-loops. There are other, less likely, possibilities. Ian
