Declare a large arary!

[truongthinhs]

I want to declare a array 2 demensions with large size. Exam: A(1000000,1000000). Can I make it in Fortran? if can how I must declare? Please, help me.
Thank you very much!

 

[xwb]

Depends on how much memory you have. Is it possible to use a disk file?

 

[truongthinhs]

I cant declare it, the program give the error like as:

Error: The size of the array dimension is too large, and overflow occurred when computing the array size. [A]
REAL,DIMENSION(0:100000,0:100000)::A.

 

[xwb]

You're talking 10^6x10^6x4 which is about 4x10^12 i.e 4Tb. Not likely that your machine has that much space. I don't even have that much disk space! Do you really need an array that size?

 

[gullipe]

Hi

I occationally use MS-Fortran 5.10 (for DOS) and there you can specify huge arrays. This declaration is in one of my programs:

byte vBits[HUGE] (2000000)

In your case it would be:

real A[HUGE] (1000000,1000000)

But maybe you are not using MS-Fortran?

Best wishes
gullipe

 

[xwb]

Huge will cope with an addressing range of a flat addressing 32 bit machine. That is outside the addressing range of a flat addressing 32 bit machine. It is just on the limit of a segmented addressing 32 bit machine which the 386 could handle but nobody ever used because it was "too difficult". As I mentioned earlier, you can dump it to disk but you would need a 4Tb disk.

The question is do you really need an array that size or can you get away with a sparse array.

 

[paoconnell]

What is the reason you're trying to create such a large array? There are other ways to work with large arrays other than in an array that would be too large for available memory.

For instance, you could implement a sparse array (look at a data structures book) and put the array elements in a database table as (x coordinate, Y coordinate, value). Whatever you were planning to do with the array will be slower, but you will be able to do work with it.

Pat