Ifort and gfortran do not use the same block size for record length by default. In ifort, the value of recl in your open statement is in 4-byte blocks, so your record length isn’t 985,600 bytes, it is 3,942,400 bytes long. That means the records are written at intervals of 3.9 million bytes. gfortran uses … Read more
To support the answer by Alexander Vogt, I’ll generalize. The intrinsic random_number(u) returns a real number u (or an array of such) from the uniform distribution over the interval [0,1). [That is, it includes 0 but not 1.] To have a discrete uniform distribution on the integers {n, n+1, …, m-1, m} carve the continuous … Read more
The cubature package does 2D (and N-D) integration using an adaptive algorithm. It should outperform simpler approaches for most integrands.
The languages have similar feature-sets. The performance difference comes from the fact that Fortran says aliasing is not allowed, unless an EQUIVALENCE statement is used. Any code that has aliasing is not valid Fortran, but it is up to the programmer and not the compiler to detect these errors. Thus Fortran compilers ignore possible aliasing … Read more
To answer your question: Yes Fortran does preserve the value of internal variables through function and subroutine calls. Under certain conditions … If you declare an internal variable with the SAVE attribute it’s value is saved from one call to the next. This is, of course, useful in some cases. However, your question is a … 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 way to do this now is to use the Fortran ISO C Binding on the Fortran side. This is part of the Fortran 2003 language standard and is available in many compilers; it is not specific to gcc. It has been described in many answers on this site. As part of the language standard, … Read more
Yes, Fortran has procedure pointers, so you can in effect alias a function name. Here is a code example which assigns to the function pointer “f_ptr” one function or the other. Thereafter the program can use “f_ptr” and the selected function will be invoked. module ExampleFuncs implicit none contains function f1 (x) real :: f1 … Read more