truncating a long for loop

i wrote a program and it includes a for loop, on running this program matlab says the "for loop is too long, truncating to..."

what does this mean and how does it affect my program?

Answer 1

[Jos (10584)]

Similar to this?

N = Inf ;
for k=1:N,
   if k > 10, break ; end
end

which will get you a warning: Warning: FOR loop index is too large. Truncating to 9223372036854775807.

So, check your N!

[Talaria]

i know my N is big, actually my N=2^41 my question is whether the loop will complete to N or it will terminate early, is that what truncating means? if not then what does it mean? And does that depend on my computer??

[Jan]

Here truncating mean, that the FOR loop cannot "carry" such a large index vector. This is a problem of the internal representation of numbers.

Imagine the processing of a loop iteration takes 1e-3 seconds (a fair assumption). How long will it take to perform 2^41 iterations?