What advantages does modern Fortran have over mode

Question

I'm trying to decide between Fortran and C++ for an application in scientific computing. It's not clear to me if Fortran still has advantages over other languages when it comes to performance. For example, I believe since Fortran enforces strict aliasing, better optimizations could be made by the compiler when compared to C before C99. I'm unsure of how C++ fits in here.

Any guidance?

Answer 1

With the emergence of template-meta programming (especially expression templates), C++ reached FORTRAN's league in numerical computations, so speed should not be an issue anymore. However, there's still some things to be said about other issues:

Pro FORTRAN: The older folks might know it better than C++.
Contra FORTRAN: It's a disgusting, old, and mostly abandoned language, that's already outdated the moment your start your project. Whoever learns programming now, is very unlikely to learn FORTRAN, so you might run into problems finding programmers for the project later.

Pro C++: It's relatively modern, with compilers still improving in considerable strides. It allows you to write quite expressive code.
Contra C++: Some of those template error messages will make you weep.

Answer 2

The other major issue is the learning curve which is very huge for C++ and exceptionally small for Fortran (90 and later). Fortran is like MATLAB with operations like ...

• B'DB is matmul( matmul(transpose(B), D), B )
• L2 norm of a vector is norm2(x)
• SVD of a matrix using LAPACK is call gesvd(A,S,u,vt)

Fortran also has pointers, dynamic memory, user defined data types etc.

It is well supported by major vendors (Intel/Sun/IBM/Cray/PGI/NAG etc.), open source (gfortan/g95) communities and developers of numerical library/APIs such as PETSc, MPI etc.

Heck the new standard (Fortran 2008) even has co-arrays for doing parallel programming without the need for MPI/OpenMP and some Fortran compilers already support it (g95 and Cray).

Basically it has all the good qualities required for numerical computing, is easier than MATLAB, is standardized, free, scalable (with MPI/OpenMP and co-arrays), produces blazing fast/parallel code.

For numerics nothing beats Fortran but unfortunately for anything else everything beats Fortan. So if you are a scientist with a safe job and only do numerical/HPC computing then stick with Fortran otherwise learn and use C++ as it is widely used for non numerical software.

Answer 3

I am new to programming.I have been programming in the field of finite elements for about a year. After some research on the net I decided to use fortran 2003.I learned to program in the modular style in about ten days by studying the Chapman book. It's one year on and i have written about four thousands of code lines in modular format(maintainable,reusable and neat codes) and haven't used any character variable at all. I don't think that by studying C++,matlab,python,java ... for ten days you would be able to write numerical codes as efficient as in fortran. fortran 2003 also has all the necessary OOP capabilities which I am learning now. So in terms of language strength in the numerical aspect fortan doesn't lack anything(modular style,OOP style,powerful array capabilities,powerful libraries, free and commercial up to dated compilers,very easy to learn, very efficient ...). Languages like python/numpy has most of these capabilities but lack efficiency. Languages like C++ also has most of the capabilities of fortran(although for array computation which is the main core of numerical computation you have to import some libraries!!), but maybe a program written by someone like me in fortran would be more efficient than one written by some c++ programmer with 10+ years of experience.
Finally I do my heavy numerical computations in fortran(modular or OOP format), and use python\numpy for small size computations(like creating plots,small size array computations ... ).

Answer 4

Given the existence of scientific computing packages like LAPACK++, which are highly optimized already, modern Fortran doesn't even have a performance advantage. C++ may have its faults, but performance is not one of them.

Answer 5

Fortran allows whole array operations and also operations on array sections. There are C++ classes for arrays, but I don't think you can refer to a slice such as x(:,2:,1:N3:2) as easily as in Fortran. This lets one express some algorithms pretty concisely.

The convenience of Fortran's array operations extends to arrays of derived types. Suppose you have a an array of dates:

type date
integer :: month,day,year
end type date

type(date) :: x(1000)

Then x refers to the array of dates, x%month refers to the array of months, and pack(x,x%month==1) refers to all dates in January. How many other programming languages offer this convenience?

Some of the earlier comments about Fortran -- "old and disgusting" -- are biased and should be discounted accordingly. Let me argue the opposite. In my opinion the free format of Fortran 90 looks better than the syntax of C and C++, with the curly braces and semicolons. Leaving them out or incorrectly putting them in can cause errors in C and C++ that have no counterpart in Fortran.

Answer 6

I took a look at some of the stuff in the latest Fortran standards, and frankly I'm impressed. A lot of what I hated about the language 20 years ago is gone now. No more line numbers and special columns (may they burn in hell).

Fortran has been heavily used in engineering circles for 50 years now. That gives you two advantages if you work in those circles. First off, these folks care a lot about optimization. That means Fortran compilers tend to have the best optimizers around. The language itself is a lot more optimizable than Cish languages too, thanks to its lack of aliasing.

The second advantage is that Fortran's library support for number crunching simply cannot be beat. The best code is nearly always going to be the well-debugged code you don't have to write.

If your application doesn't fall under scientific, engineering, or number crunching in general, then neither of the above will be a big deal for you, so you may be better off looking elsewhere.