CODEWITHSUNDEEP
filefortranfortran90fortran95
Peaceful
Peaceful

Reputation: 5450

Read the contents of a file again and again in Fortran 95

I want to read entries from a huge file (more than 10^10 rows) inside a loop. Since file is huge, I am reading one element at a time, using it and then reading the next element and so on. Thus, I have something like this:

DO i = 1, 10
    open(unit = 1, file = 'myfile.dat')
    Do j = 1, 10^10
         read(1, *)x
         !Use x here
    Enddo
    close(1)
ENDDO

This works fine when the outer loop runs a small number of times. However, when I want try to run it many more times, (say 100 to 1000), my computer gets hung or throws an error : Not enough space on \tmp. I looked at this but that didn't solve my issue. My primary guess is that this is happening because each time I re-open the file, it gets stored in RAM or tmp but I am not sure about this. In this context, can anybody tell me a better way to load file only once but read the contents over and over ?

Upvotes: 0

Views: 1464

Answers (1)

Ricardo Torres
Ricardo Torres

Reputation: 36

You don't have to close the file, just "rewind" it:

open(newunit = iunit, file = 'myfile.dat') !no need to specify the number, the compiler will do it for you, iunit is an integer
do i = 1, 10
    do j = 1, 10**10                       !fortran compilable
         read(iunit, *)x
         !Use x here
    end do
    rewind(iunit)        
end do

close(iunit)

Upvotes: 2

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