I am working on a complicated code and have made a few changes. The main purpose of the code is to open two files and perform calculations by taking data from each file a record at a time. These files are very large and are unformatted.
My first change was to save these files using the segmented filetype flag, and also to have the code read them in as segmented. This works fine.
My next change was to convert a REWIND into a BACKSPACE, this is what my code looks like:
if (kneed .le. kbeg) then
kback=kbeg-kneed
if(kback.le.5)then
do i=1,kback
backspace ivec
end do
else
rewind ivec
do 10 i=1,kneed+6
read(ivec)
10 continue
end if
end if
What's happening here: IVEC is the handle for the file. FILE1 is read through sequentially, as in, 1, 2, 3, 4,....N. Then, for each N in FILE1, FILE2 is read twice, and a calculation is performed between the record N in FILE1 and both records N-1 and N+1 for FILE2. i.e. calculation(FILE1_N, FILE2_N-1) and calculation(FILE1_N, FILE2_N+1).
In the code, kbeg is the current record of FILE2, kneed is the desired record.
This is where the REWIND was necessary, FILE2 needed to be rewound to get to the N-1 for the subsequent N+1 (FILE1) calculation. My issue was that this REWIND proved to be the biggest bottleneck, I am trying to speed it up by implementing this IF statement to do a BACKSPACE (before my modification only the statement in the ELSE section was present, the "+6" is there because my files have a 6 line header before the records begin).
THE PROBLEM: Now I have made this change, the BACKSPACE appears to be speeding up the process, but now when I read the FILE2 records the data are different from when I just used the REWIND function. The logic here seems fine, and it actually works for the first time I do this to FILE2, but after that the data appear to be wrong.
I'm wondering if there is something about segmented records that I need to be aware of for the BACKSPACE to work properly. Also, my kneed and kbeg are appearing correctly. The only issue is when I read my data into an array the data are different from when only the REWIND function is present.
Am I missing something?
Please advise me if I need to provide more info!
