Why doesn't the FFT library have a deterministic behavior?

[nielsvanetten]

So I'm benchmarking the dsp FFT from the library, but it seems every time I let it be run by the VCK190 the cyclecount is different.
I know there is a variable:
/*TP_DYN_PT_SIZE selects whether (1) or not (0) to use run-time point size determination.*/

But if declare 1, the ai-engine gets stuck (also in simulation).

Is this behavior to be expected?