Personally I now write use, intrinsic :: iso_fortran_env which includes parameters such as int32,real64 which have the obvious meanings, and can be used like this: real(real64) :: a_64_bit_real_scalar Note that kind=8 is not guaranteed, by the standard, to deliver an 8-byte kind. The values that kind parameters take are not standardised and do vary from … Read more
The big problem is that you did not include the last arg ierr in the call to MPI_Gather. The doc said All MPI routines in Fortran (except for MPI_WTIME and MPI_WTICK) have an additional argument ierr at the end of the argument list. In addition to that, my advise is to always stick to good … Read more
It is call action(mySubX) provided action looks as subroutine action(sub) !either – not recommmended, it is old FORTRAN77 style external sub !or – recommended interface subroutine sub(aA, aB) integer,intent(…) :: aA, aB end subroutine end interface ! NOT BOTH!! call sub(argA, argB) provided action knows what to put there as argA, argB to represent aA, … Read more
Strings of dynamic length are always a bit tricky with the C interaction. A possible solution is to use pointers. First a simple case, where you have to hand over a null-character terminated string to a C-Function. If you really pass the string only in, you have to ensure to finalize it with the c_null_char, … Read more
In principal when a module goes out-of-scope, the variables of that module become undefined — unless they are declared with the SAVE attribute, or a SAVE statement is used. “Undefined” means that you are not allowed to rely on the variable having the previous value if you again use the module — it might have … Read more
When compiling with ifort before version 17.0.1, the default behaviour is for the compiler not to use the Fortran rules for automatic allocation on intrinsic assignment. You will need to use an option like -assume realloc-lhs.
This is a question crying out for a canonical one, really. In the interest of answering your specific question in the absence (as far as I can tell, but I may write one eventually), I’ll answer. The argument to size must not be an unallocated allocatable variable. For your code fred is an allocatable variable. … Read more
In general the answer to your first question is Yes and I’ll come to an answer to your second question in a moment. Note first that this is a general answer to a general question and the bright sparks who hang around SO Fortran questions may well come up with special circumstances in which modules … Read more
Fortran doesn’t support anonymous functions. The simple work around is to write a function that has a name. There are then two possible approaches in modern Fortran for capturing the value of any additional parameters required for the function beyond the variable being minimised: The procedure to be minimised is expressed as a deferred binding … Read more
In years past, ignoring this use of the first column could cause bad things on a line printer, like page ejects — but when was the last time that you saw a line printer? Otherwise it was output device, compiler and OS dependent. The advice of “Fortran 95/2003 for Scientists and Engineers” was excellent for … Read more