Introduced at the same time as the result was recursion. Before we get to how a recursive function comes about, some clarification on what a result variable is. The function result is always returned through a result variable, whether result is used or not.1 With result the result variable has the name specified, and without … Read more
The 8 refers to the number of bytes that the data type uses. So a 32-bit integer is integer*4 along the same lines. A quick search found this guide to Fortran data types, which includes: The “real*4” statement specifies the variable names to be single precision 4-byte real numbers which has 7 digits of accuracy … Read more
Yeah, pointer arrays are funny in Fortran. The problem is that this: TYPE(domain),DIMENSION(:),POINTER :: dom does not define an array of pointers, as you might think, but a pointer to an array. There’s a number of cool things you can do with these things in Fortran – pointing to slices of large arrays, even with … Read more
You have some lengths 12 in the constructor, so it may be better to use length 12. Also, use instead character(len=12), dimension(5) :: models = [character(len=12) :: “feddes.swp”, & “jarvis89.swp”, “jarvis10.swp”, “pem.swp”, “van.swp”] Possibly even better, if you have compiler support, is character(len=*), dimension(*) :: …
Bare minimum -Og/-O0 -O0 basically tells the compiler to make no optimisations. Optimiser can remove some local variables, merge some code blocks, etc. and as an outcome it can make debugging unpredictable. The price for -O0 option is very slow code execution, but starting from version 4.8 GCC compilers (including the Fortran one) accept a … Read more
What you care about here is association: you want to be able to associate entities in the function f with those in the subroutine condat. Storage association is one way to do this, which is what the common block is doing. There are other forms of association which can be useful. These are use association … Read more
The form real, dimension(:) :: arr declares an assumed-shape array, while the form real :: arr(*) declares an assumed-size array. And, yes, there are differences between their use. The differences arise because, approximately, the compiler ‘knows’ the shape of the assumed-shape array but not of the assumed-size array. The extra information available to the compiler … Read more
The implicit statement (including implicit none) applies to a scoping unit. Such a thing is defined as BLOCK construct, derived-type definition, interface body, program unit, or subprogram, excluding all nested scoping units in it This “excluding all nested scoping units in it” suggests that it may be necessary/desirable to have implicit none in each function … Read more
If a procedure has a dummy argument that is an allocatable, then an explicit interface is required in any calling scope. (There are numerous things that require an explicit interface, an allocatable dummy is but one.) You can provide that explicit interface yourself by putting an interface block for your subroutine inside the main program. … Read more