savoie@nsidc.org wrote:
> David Fanning <davidf@dfanning.com> writes:
>
>
>> Andres writes:
>>
>>
>>> Hi all,
>>>
>>> does somebody knows how to read this (fortran way)
>>>
>>> do 210 j=1,ngr2
>>> write(10) real(rhoc(j)),
>>> 2 real(psi1(j)),real(psi2(j)),real(psi3(j))
>>> write(10) aimag(rhoc(j)),
>>> 2 aimag(psi1(j)),aimag(psi2(j)),aimag(psi3(j))
>>> 210 continue
>>>
>>> in IDL? I managed, but it takes forever for big "ngr2". This is what I
>>> do:
>>>
>>> rhoc=fltarr(ng3)
>>> psi1=fltarr(ng3) & psi2=fltarr(ng3) & psi3=fltarr(ng3)
>>>
>>> For i=0l,ng3-1l do begin
>>> readu,lun,tmp1,tmp2,tmp3,tmp4
>>> rhoc[i]=tmp1
>>> psi1[i]=tmp2
>>> psi2[i]=tmp3
>>> psi3[i]=tmp4
>>> Endfor
>>>
>>> but this takes a long time... Anybody knows a fast way?
>>
>> Here is an article for you to read:
>>
>> http://www.dfanning.com/tips/ascii_column_data.html
>
>
>
> I don't think he's reading ascii data. I think he's reading a long list of
> floats?
Same principle though.
> If the problem is that the data is in Fortran order, shouldn't he be reading
> into a large array and then transposing?
>
> how about (assuming ngr2 * 4 * sizeof(float) < memory available):
The data is written 4 numbers at a time, with 2 sets of ngr2 sets of numbers. Additionally, each set
of 4 numbers is a separate record (with the attendent record markers). So how about:
; Open the file as "direct" access.
openr, lun, filename, /get_lun ; No /f77_unformatted
; create the data array and read the data
; Dimension 1 indices 0 and 5 are for the Fortran record markers
; Dimension 2 indices are for the real and imaginary bits
data = fltarr( 6, 2, ngr2 )
readu, lun, data
; strip out the real numbers
rrhoc = reform(data[1,0,*])
rpsi1 = reform(data[2,0,*])
rpsi2 = reform(data[3,0,*])
rpsi3 = reform(data[4,0,*])
; strip out the imaginary numbers
irhoc = reform(data[1,1,*])
ipsi1 = reform(data[2,1,*])
ipsi2 = reform(data[3,1,*])
ipsi3 = reform(data[4,1,*])
Also, totally untested, but you get the idea. You can also transpose the data array before stripping
out the real and imaginary bits so you don;t need a REFORM on every line to remove unity dimensions.
paulv
>
>
> pro read_fortran
>
> ;; The data is 4 columns x ngr rows, but Fortran is stored row major.
> data = make_array( ngr2, 4, /float )
> openr, lun, "your_file_name", /GET_LUN
> readu, lun, data
> col_row_data = transpose( data )
>
> rhoc = col_row_data[ 0, * ]
> psi1 = col_row_data[ 1, * ]
> psi2 = col_row_data[ 2, * ]
> psi3 = col_row_data[ 3, * ]
>
> end
>
>
> Is this sort of what you're looking for? Completely untested of course.
>
> Check out this fanning article for colum/row major information/headache.
>
> http://www.dfanning.com/misc_tips/colrow_major.html
>
>
> Hope this helps.
>
> Matt
>
--
Paul van Delst
CIMSS @ NOAA/NCEP/EMC
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