Efficient use of Fortran 95

The following notes relate to features introduced into the Fortran 95 standard.

  • FTN95 produces faster code with ALLOCATABLE arrays as against POINTER arrays because the ALLOCATABLE attribute guarantees contiguous storage and no aliasing.

  • Temporary arrays (required only during the life time of a function call) are better implemented using automatic arrays in preference to ALLOCATABLE arrays because these can be allocated more efficiently.

  • Fixed-size arrays are more efficient than variable-sized arrays so, when the logic of the program and memory constraints allow, fixed-size arrays are preferred.

  • Specifying the INTENT attribute of a dummy argument improves diagnostics and helps the optimiser and code generator.

  • The use of ENTRY and EQUIVALENCE prevents certain optimisations from taking place.



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