VBA Efficiency - Calculating on the "background" and passing to range -


it's been month since i've started studying , practicing vba in excel , first time ask question in forum, keep in mind.

the problem this:

  • i have sheet 300k rows , 10 columns
  • each row result of calculation made in script
  • the whole script takes 2min31s run
  • i'm using ranges , options speed (e.g. "application.calculation = xlmanual", etc)

is safe think performing calculations on memory variable faster using range? i've simplified code use example:

option 1 - how i'm doing right now

for = 0 300000      sheet.cells(i,1).value = i^2 next

option 2 - in head run faster

for = 0 300000      variable(i) = i^2 next  'this doesn't work it's illustrate i'm looking sheet.range(cells(1,1),cells(300000,1)).value = variable

can done? can pass values of array range @ once, avoiding looping through each cell of range?

yes faster, however, need 2 dimensional array of variants.

dim variable(1 1, 1 300000) ' long row (but long row) dim variable(1 300000, 1 1) ' long column

this way save time because pass data through interface once , not 300000 times. , calling method set value property has fix cost because sub in vba editor in same process different apartment excel, cross boundary rpc (remote procedure call) used.

btw, if want know if performance improvement works, should measure it, this:

debug.print "started: " & now() ' code debug.print "finished: " & now()

update

i tried, , work 1 dimensional arrays. in case interpreted long row. however, think it's better use 2 dimensional array version because (1) cleaner (easy see data like) , because (2) data in same format if read range.

update two

so run these:

public sub slowmethod(optional citerations long = 300001)     debug.print "started: " & now()     dim long: = 0 citerations - 1         activesheet.cells(1 + i, 1).value = ^ 2     next     debug.print "finished: " & now() end sub  public sub fastmethod(optional citerations long = 300001)     debug.print "started: " & now()     dim variable() variant: redim variable(1 citerations, 1 1)     dim long: = 0 citerations - 1         variable(1 + i, 1) = ^ 2     next     activesheet.cells(1, 1).resize(citerations, 1).value = variable     debug.print "finished: " & now() end sub

and received:

slowmethod started: 2017.04.06. 15:57:54 finished: 2017.04.06. 15:58:56 fastmethod started: 2017.04.06. 15:59:02 finished: 2017.04.06. 15:59:02

so less 1 second vs more 1 minute.


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