loop ↔ vectorized ↔ direct [Two-Stage / GS Designs]

posted by ElMaestro  – Belgium?, 2017-08-20 15:22  – Posting: # 17721
Views: 24,353

Hi Hötzi,

» Later down you makes calls to vecQT1[df] and vecQT2[df]. That’s awfully slooow. Why not simply call qt(p=foo, df=bar) directly?

That kind of benchmarking is misleading. Here you are doing the vectorise operation of array generation numerous times which will never happens in practice; you only need to initialise the arrays once within every run of 1000000 iterations, possible even keep the arrays/vectors across runs.

I agree that whole "once" operation is faster when you use
vecQT1 <- qt(p=1-alpha1, df=1:5000)
(I had no idea you could do that, actually)
, but if you benchmark the entire you you will see the difference may be a few microsecs out of numerous seconds or minutes. Saving 0.0001% time? That's not optimization, it beautification or achieving the same with fewer lines of code which isn't what I am after.

I am not very experienced with vectorised functions at all - I understand code better if loops are visible.:-D That's just me, of course.

I could be wrong, but...

Best regards,
ElMaestro

"Pass or fail" (D. Potvin et al., 2008)

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