Hi you suggested changes to the loop code reduced run time from 41 seconds to 29 seconds but still doesn't compare to the ¨/⌷/⊂ code at 50 msec size of data is 30000 and i ran in a ram drive
Has anyone tried this on some faster machines? I'm going to run all on a rasp pi and see what times are On Wed, 1 6 Jun 2021 12:35:25 +0200 Dr. Jürgen Sauermann <m...@xn--jrgen-sauermann-zvb.de> wrote: > Hi, > > the biggest problem with your old loop code is its quadratic runtime. > > The statement > > rs←rs,ar[a[i]; b[i]] > takes more and more time as rs grows. GNU APL has occasionally been > blamed for being slow, but in most cases the above coding pattern was > the real reason. A faster way in your old loop code is to: > > rs←(⍴A)⍴0 > > before the loop and then > > rs[i]←ar[a[i]; b[i]] > > inside the loop, which takes only linear time. > > In general: never use , or ⍪ inside a (long) loop, even > though the code may look more intuitive or elegant. > > Best Regards, > Jürgen > > > On 6/16/21 4:39 AM, enz...@gmx.com wrote: > > Hi > > thanks for this code - first time actually using ¨ and ⌷ > > in my comparison test on an old hp dual core linux machine - with only > mplayer running > with ⍴a and ⍴b 29882 chars > > according to ⎕ts my loop code takes ~39 seconds to put results into rs > 2021 6 15 19 46 11 277 > 2021 6 15 19 46 50 354 > > and the new code takes ~50 msec to put results into rs1 yes msec vs > seconds what is that 39000 msec vs 59 msec > 2021 6 15 19 46 50 354 > 2021 6 15 19 46 50 404 > > +/rs1=rs and rs and rs1 don't exist before running them in fns > 29882 > > ---- > > the only problem i have is in a fresh ws running the )copy as > > ⍎')copy mn9 mn9 is a file which has a string of 29882 chars assigned to > mn9←'xxxxx' in it > a←mn9 gives mn9 value error consistently - though when i check > the )vars it is there and complete - running it in ram drive has no effect > > the unquoted ')copy' doesn't actually finish coping the file into the ws as > fast as the code returns and goes to the next line > > no real problem as i usually hard code the sequnces (cutnpaste) into the > script - but with some in the 100K range i will have to do the )copy manually > and run in workspace > > thank you for giving me this code - much appreciated > > > > On Tue, 15 Jun 2021 15:20:27 +0200 > Dr. Jürgen Sauermann <m...@xn--jrgen-sauermann-zvb.de> wrote: > > Hi, > > how about: > > (a,¨b)⌷¨⊂ar > 11 22 33 44 44 33 22 11 > > > Best Regards, > Jürgen > > > On 6/15/21 2:45 AM, enz...@gmx.com wrote: > hello > > i've been using this looping for array work but there has to be a better apl > way of coding the indexing of the ar array > any suggestions > > > > ∇rs←lp;a;b;ar;i > 'lp' > 'ar' > +ar←4 4⍴11 12 13 14 21 22 23 24 31 32 33 34 41 42 43 44 > 'a ' > +a←1 2 3 4 4 3 2 1 > 'b ' > +b←1 2 3 4 4 3 2 1 > i←1 > rs←⍴0 > sp: > rs←rs,ar[a[i]; b[i]] > →((i←i+1)⍴a)/sp > '' > ∇ > > > > >
