On Sat, 17 Mar 2007, Lasse Clausen wrote:
> On 16 Mar, 21:23, David Fanning <n...@dfanning.com> wrote:
>> Paul van Delst writes:
>>> I know you didn't intend to suggest hardwiring 99 different fileid's :o)
>>
>> With Cut and Paste it's not so bad. Of course, you
>> spend the next five hours fixing typos, but... :-)
>>
>> Cheers,
>>
>> David
>>
>> --
>> David Fanning, Ph.D.
>> Fanning Software Consulting, Inc.
>> Coyote's Guide to IDL Programming:http://www.dfanning.com/
>> Sepore ma de ni thui. ("Perhaps thou speakest truth.")
>
> Well thanks, that works, however it did not bring the speed boost I
> had hoped for. So I had another thought: Actually, all data is one
> line, not in one line per station as I said earlier. But I know that
> each data set is 1440 characters long, so here is the outline of my
> code, after I opened all the files:
>
> info = file_info(input_filename)
> lines = info.size/1440L
>
> for i=0L, lines-1L do begin
> point_lun, fin, i*1440L
> readf, fin, line, format='(A1440)'
> ; extracting station name
> hstat = strlowcase(strmid(line, 12, 3))
> ; find correct file unit
> tmp = where(stats eq hstat)
> printf, tmp[0]+1, line
> endfor
>
> I chose the above solution because my favoured one:
>
> while not(eof(fin)) do begin
> readf, fin, line, format='(A1440)'
> hstat = strlowcase(strmid(line, 12, 3))
> tmp = where(stats eq hstat)
> printf, tmp[0]+1, line
> endwhile
>
> does not seem to work in the way I expected, i.e. read 1440 byte,
> parse station, write data, read next 1440 byte... until end of file.
> Rather, it reads the first 1440 bytes and then hits the end of the
> file (while loop is executed once). So that is why I wondered what the
> readf command with the above format code actually does. Since it hits
> the end of file border after the first read command, I suspect it
> actually reads in all data, and then extracts the first 1440 bytes
> from that. Which would explain why the solution I am running now (with
> the for loop) is so slow: about 20 seconds for 3000 lines (4MB file).
> On some chunky Sun server, mind you. Any more ideas?
>
> Cheers
> Lasse
>
>
what about something like this:
finarr=assoc(fin, bytarr(1440))
for nrec=0l,lines-1l do begin
line=finarr[nrec]
hstat = strlowcase(line[12:14])
tmp = where(stats eq hstat)
writeu, tmp[0]+1, line
endfor
regards,
lajos
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