Memory storage of multidimensional arrays in fortran 90

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SUMMARY

In Fortran 90, multidimensional arrays may be stored non-contiguously in memory, depending on the compiler used. Both Intel Fortran Compiler (ifort) and GNU Fortran (gfortran) adhere to this flexibility. While the language does not enforce a specific storage implementation, it is generally accepted that the first index of an array is contiguous. Subarrays defined with strides, such as A(1:50:10), are not contiguous and are typically copied to a contiguous temporary when passed as arguments.

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  • Understanding of Fortran 90 array structures
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  • Knowledge of memory storage concepts
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Hello,

I think i heard somewhere that a multidimensional array in fortran 90 may be stored non-contiguously in memory. Is this true? Even if it the size was known at compile time?

If your answer is it depends on a compiler, what about ifort and gfortran?
 
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OK, after some investigation, I found that fortran 90, unlike fortran 77 (and C) does not impose a storage implementation on the arrays. But, according to some people, in all implementations at least the first index is contiguous. What is certainly not contiguous are subarrays chosen with a stride of course (A(1:50:10)), though when used as an argument they are usually copied to a contiguous temporary. The pointers to such arrays are also not contiguous.
If arrays are defined with a simple format, e.g. A(10,20,30), they are, in most (all?) cases contiguous.

Any further comments or clarifications would be welcome.
 

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