| Re: Multidimensional arrays and CALL_EXTERNAL [message #60828] |
Fri, 20 June 2008 13:21  |
Foldy Lajos
Messages: 268
Registered: October 2001
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Senior Member |
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On Fri, 20 Jun 2008, Dan wrote:
> Hi Lajos,
>
> This doesn't seem to be working for me.
>
Create a 4D array in IDL: arr=lindgen(2,3,4,5). Pass this array to
the C routine, and print the array elements in C. You will see the
pattern.
regards,
lajos
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| Re: Multidimensional arrays and CALL_EXTERNAL [message #60830 is a reply to message #60829] |
Fri, 20 June 2008 11:24  |
Foldy Lajos
Messages: 268
Registered: October 2001
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Senior Member |
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On Fri, 20 Jun 2008, Dan wrote:
> Hi everyone,
>
> Now that I have gotten CALL_EXTERNAL to work correctly, I am trying to
> figure out how IDL stores multidimensional arrays in memory. Since
> CALL_EXTERNAL passes an arrays by reference (pointer to the first
> element of the array), the multidimensional arrays in C act like a 1-D
> array. I have figured out how to access elements of a 2D array
> (array(i, j) ---> array[i + i_size * j]), but haven't been able to
> figure out how to access elements from a 4D array.
>
> For example, how would I access element:
> array(i, j, k, m) from the pointer in C?
>
I have never used CALL_EXTERNAL, but my guess is:
array(i, j, k, m) ---> array[i
+ i_size * j
+ i_size * j_size * k
+ i_size * j_size * k_size * m]
regards,
lajos
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| Re: Multidimensional arrays and CALL_EXTERNAL [message #60968 is a reply to message #60829] |
Mon, 23 June 2008 05:15 |
Allan Whiteford
Messages: 117
Registered: June 2006
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Senior Member |
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Dan wrote:
> Hi Lajos,
>
> This doesn't seem to be working for me.
Dan,
It works for me; as an example:
multi.c
-------
#include <stdio.h>
#include "idl_export.h"
void do_work(float *a)
{
printf("%f\n",a[3+5*10+7*10*20+9*10*20*30]);
}
IDL_VPTR multi(int argc, IDL_VPTR argv[])
{
do_work((float *) argv[0]);
}
multi.pro
---------
pro multi
a=fltarr(10,20,30,40)
a[3,5,7,9]=3.14
junk=call_external('multi.so','multi',a,/unload)
end
Compile
-------
gcc -I /usr/local/rsi/idl/external/include -shared multi.c -o multi.so
does the above work for you? Can you post an example of code which fails?
Thanks,
Allan
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