| Re: Read & write data files b/w IDL & Fortran 90 [message #39009] |
Wed, 14 April 2004 13:56 |
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Paul Van Delst[1]
Messages: 1157
Registered: April 2002
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Senior Member |
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bridgemat wrote:
> Hey, thanks Paul! I'll give it a try. My actual data is all float/real
> kind of stuff, so I hopefully wouldn't have this problem there. I was
> just trying to see if I could do it with an "easy" case, but I guess
> simple isn't always easy! :)
Hello,
Best thing is to present the case that is causing the problem.
You're right, though. You shouldn't have the problem I rabbited on about with regular
floats - assuming you have the default declarations in IDL, e.g.
x = 0.0
and Fortran90,
REAL :: x
x = 0.0
If you have either
; IDL
x = 0.0d
or
; Fortran90
INTEGER, PARAMETER :: dp = SELECTED_REAL_KIND( 15 )
REAL( dp ) :: x
x = 0.0_dp
but not both, then the same problem may be occurring.
BTW, I read/write datafiles in IDL and write/read them in Fortran90 all the time (both the
sequential and direct unfromatted variety). Never had any problems - as long as I'm on
the same system. Otherwise you may have byte-sex issues, i.e. reading files created on a
little-endian system (PC,Alpha) on a big-endian one (IBM,SGI,Sun,HP,...) or vice-versa.
paulv
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| Re: Read & write data files b/w IDL & Fortran 90 [message #39010 is a reply to message #39009] |
Wed, 14 April 2004 13:45  |
bridgemat
Messages: 6
Registered: August 2003
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Junior Member |
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Hey, thanks Paul! I'll give it a try. My actual data is all float/real
kind of stuff, so I hopefully wouldn't have this problem there. I was
just trying to see if I could do it with an "easy" case, but I guess
simple isn't always easy! :)
-Bridget
Paul Van Delst <paul.vandelst@noaa.gov> wrote in message news:<c572r2$tuc$1@news.nems.noaa.gov>...
> Paul Van Delst wrote:
>> bridgemat wrote:
>>
>>> I did try the /f77_unformatted keyword when writing the original file,
>>> but I still couldn't get it to work. It shouldn't have anything to do
>>> w/ using Fortran 90 instead of 77, right? Or am I doing something
>>> altogether wrong in my Fortran program?
>>
>>
>> Hello,
>>
>> I just grabbed both your codes and mucked about and had a "d'oh" episode.
>>
>> You create the data in IDL using INDGEN == 2 byte ints. In your f90 code
>> you read the data with the default int which is 4 bytes. That's why
>> you're getting the I/O error.
>>
>> Two options:
>>
>> 1) In IDL create the data like so:
>> test=LINDGEN(3,4,5)
>> And read it with your current f90 code.
>>
>> Or
>>
>> 2) Create the data file with your current IDL code and in Fortran90,
>> define your integer arrays like so:
>> INTEGER, PARAMETER :: ip = SELECTED_INT_KIND(4)
>> INTEGER(ip), DIMENSION(3,4,5)::arr_in,arr_out
>>
>> The integer kind parameter from SELECTED_INT_KIND(4) should give you the
>> kind type for a 2-byte integer.
>>
>> I prefer option (1) coz it's the simplest, but YMMV.
>
> Apologies for my own followup, but in either option above you'll still need the
> /f77_unformatted keyword in the IDL routine.
>
> cheers,
>
> paulv
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| Re: Read & write data files b/w IDL & Fortran 90 [message #39048 is a reply to message #39010] |
Fri, 09 April 2004 13:44 |
Paul Van Delst[1]
Messages: 1157
Registered: April 2002
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Senior Member |
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Paul Van Delst wrote:
> bridgemat wrote:
>
>> I did try the /f77_unformatted keyword when writing the original file,
>> but I still couldn't get it to work. It shouldn't have anything to do
>> w/ using Fortran 90 instead of 77, right? Or am I doing something
>> altogether wrong in my Fortran program?
>
>
> Hello,
>
> I just grabbed both your codes and mucked about and had a "d'oh" episode.
>
> You create the data in IDL using INDGEN == 2 byte ints. In your f90 code
> you read the data with the default int which is 4 bytes. That's why
> you're getting the I/O error.
>
> Two options:
>
> 1) In IDL create the data like so:
> test=LINDGEN(3,4,5)
> And read it with your current f90 code.
>
> Or
>
> 2) Create the data file with your current IDL code and in Fortran90,
> define your integer arrays like so:
> INTEGER, PARAMETER :: ip = SELECTED_INT_KIND(4)
> INTEGER(ip), DIMENSION(3,4,5)::arr_in,arr_out
>
> The integer kind parameter from SELECTED_INT_KIND(4) should give you the
> kind type for a 2-byte integer.
>
> I prefer option (1) coz it's the simplest, but YMMV.
Apologies for my own followup, but in either option above you'll still need the
/f77_unformatted keyword in the IDL routine.
cheers,
paulv
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| Re: Read & write data files b/w IDL & Fortran 90 [message #39049 is a reply to message #39048] |
Fri, 09 April 2004 13:37 |
Paul Van Delst[1]
Messages: 1157
Registered: April 2002
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Senior Member |
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bridgemat wrote:
> I did try the /f77_unformatted keyword when writing the original file,
> but I still couldn't get it to work. It shouldn't have anything to do
> w/ using Fortran 90 instead of 77, right? Or am I doing something
> altogether wrong in my Fortran program?
Hello,
I just grabbed both your codes and mucked about and had a "d'oh" episode.
You create the data in IDL using INDGEN == 2 byte ints. In your f90 code you read the data
with the default int which is 4 bytes. That's why you're getting the I/O error.
Two options:
1) In IDL create the data like so:
test=LINDGEN(3,4,5)
And read it with your current f90 code.
Or
2) Create the data file with your current IDL code and in Fortran90, define your integer
arrays like so:
INTEGER, PARAMETER :: ip = SELECTED_INT_KIND(4)
INTEGER(ip), DIMENSION(3,4,5)::arr_in,arr_out
The integer kind parameter from SELECTED_INT_KIND(4) should give you the kind type for a
2-byte integer.
I prefer option (1) coz it's the simplest, but YMMV.
cheers,
paulv
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| Re: Read & write data files b/w IDL & Fortran 90 [message #39050 is a reply to message #39049] |
Fri, 09 April 2004 13:20 |
bridgemat
Messages: 6
Registered: August 2003
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Junior Member |
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Also, I did try doing it the opposite way - creating an unformatted
file in F90 and reading into IDL using the /f77_unformatted keyword.
It almost worked. The IDL array was filled with half of the F90 array
elements, having a 0 assigned to each element in between, like this:
1 0 2
0 3 0
4 0 5
0 6 0
7 0 8
0 9 0
10 0 11
0 12 0
Could this have to do with using F90 instead of F77?
-Bridget
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| Re: Read & write data files b/w IDL & Fortran 90 [message #39051 is a reply to message #39050] |
Fri, 09 April 2004 12:35 |
bridgemat
Messages: 6
Registered: August 2003
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Junior Member |
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I did try the /f77_unformatted keyword when writing the original file,
but I still couldn't get it to work. It shouldn't have anything to do
w/ using Fortran 90 instead of 77, right? Or am I doing something
altogether wrong in my Fortran program?
-B
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| Re: Read & write data files b/w IDL & Fortran 90 [message #39060 is a reply to message #39051] |
Thu, 08 April 2004 14:45 |
Paul Van Delst[1]
Messages: 1157
Registered: April 2002
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Senior Member |
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bridgemat wrote:
> As someone who knows just the basics of IDL and the basics plus a bit
> more of Fortran 90, I'm sure this is just some rookie mistake, so
> hopefully someone out there can help me out.
>
> I'm trying to write an idl array to a file, read the file in Fortran
> 90, manipulate the Fortran array, and then write that new array to a
> file that I then read into IDL. Here's how I write the original array
> to a file:
>
> test=indgen(3,4,5)
> openw,lun,'testidl.dat',/get_lun
> writeu,lun,test
> free_lun,lun
Hello,
You need to use the /f77_unformatted keyword on the IDL open. This will stick the 4-byte
delimiter at the beginning and end of each output record. Alternatively, you can specify
direct access with a set record length in your f90 OPEN statement.
> Another issue: array dimensions! My IDL book tells me that both IDL
> and Fortran arrays are column-major. Although I've been using Fortran
> longer than IDL, I haven't done much w/ multi-dimensional arrays, so I
> looked in my Fortran book, and it says that Fortran is row-major!
> Ack!!! So does that mean my Fortran array should be declared as
> DIMENSION(5,4,3) in this case? I tried that, too, but got the same
> error...
No. Declare the IDL and Fortran arrays the same way. I can never remember what the hell
column- or row-major means. I just remember that IDL is same as Fortran, and C is the
opposite.
paulv
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| Re: Read & write data files b/w IDL & Fortran 90 [message #39061 is a reply to message #39060] |
Thu, 08 April 2004 15:00 |
wmconnolley
Messages: 106
Registered: November 2000
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Senior Member |
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bridgemat <bridgemat@yahoo.com> wrote:
> test=indgen(3,4,5)
> openw,lun,'testidl.dat',/get_lun
> writeu,lun,test
> free_lun,lun
Isn't there a /f77 keyword? Fortran is a bit weird: it adds the record
length at the start (and end) of each record; IDL needs to know you
want to write a fortran-style file.
-W.
--
William M Connolley | wmc@bas.ac.uk | http://www.antarctica.ac.uk/met/wmc/
Climate Modeller, British Antarctic Survey | Disclaimer: I speak for myself
I'm a .signature virus! copy me into your .signature file & help me spread!
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