When two different subroutines declares a SAVE variable with the same name, the two variables are actually using different memory address. They will not interrupt each other due to value change.
The intel compiler option "auto" places local variables (scalars and arrays of all types), except those declared as SAVE, on the run-time stack. It is as if the variables were declared with the AUTOMATIC attribute. so, the SAVE feature will not be destroyed by the compiler option. https://www.intel.com/content/www/us/en/docs/fortran-compiler/developer-guide-reference/2023-0/auto.html
Global variables including SAVE variables are by default shared between threads, unless declared as threadprivate. Please think carefully whether you really need SAVE, SAVE and parallel programming are very rarely good bedfellows. There are one or two good uses (see e.g.Fortran OpenMP with subroutines and functions), but if there is an alternative way to do (e.g. passing through the argument list) this will almost certainly cause you less pain in the long run.
Remark: For intel Fortran, the default option should be auto-scalar:
Example:
program save
implicit none
! Variables
print *, '1st call sub1'
call sub1()
print *, '1st call sub2'
call sub2()
print *, '2nd call sub1'
call sub1()
pause
stop
end program save
subroutine sub1()
integer IPERTW,a
SAVE IPERTW
DATA IPERTW /1/
print *,ipertw
ipertw=3
print *,ipertw
return
end
subroutine sub2()
integer IPERTW
SAVE IPERTW
DATA IPERTW /2/
print *,ipertw
ipertw=4
print *,ipertw
return
end
The output will be:
D:\workdir\temp\save\ifort>save.exe
1st call sub1
1
3
1st call sub2
2
4
2nd call sub1
3
3
Fortran Pause - Enter command or to continue.
