What advantages does modern Fortran have over modern C++? [closed]_问答_开发者

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I'm trying to decide between Fortran and C++ for an application in scientifi开发者_Go百科c 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?

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.

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.

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.

Fortran has been highly optimized for mathematical (especially matrix) like operations.

C++ has been highly optimized for object usage.

Which is more important to you.

As noted below C++ has an optimized matrix library.
But Fortran's whole purpose is optimization of mathematical processes (especially matrix operations). The fact that these optimizations are built into the foundation of the language (rather than a library) and have about a two decade head start on research over C++ I doubt (but don't know for a fact) that in this area Fortran is going to win hands down.

Advantages of fortran95 and above over c++(2003):

As previously(by user4562) mentioned short learning curve(my first language was C and i still can't master it , similar is true for C++)
(My personal opinion) Easy for code transition from Octave(for that matter Matlab)similar syntax,same modularity[I use Octave to prototype a program and rewrite in fortran95 for speed],though u can directly use octave code in C++.
dynamic memory allocation is quite straight forward.(f77 didn't have this at all!)
libraries support (u can do this in c++ as well , but its natural to use fortran)
Co-array support for parallel computing (pity only cray supports them as of feb 2011 gfortran work has started as of gfortran4.6 but still a long way to go)

in short if your program or application is purely scientific computation use fortran 95 and above if calculating a few numbers is just part of the story use C++ (or whatever u feel is better)

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 ... ).

My experience with Fortran is that it's easy to learn, clean (being highly modularized), and thus well suited to a non-programmer whose main concern is doing highly optimized numerical computations. Although equal optimization can be performed in c++, (even perhaps to a greater extent), it takes a lot of instrinsic understanding to achieve those level of optimizations. When it comes to matrix calculations, out-of-the box a Fortran compiler will normally out-perform a c++ compiler. I'd also add that Fortran has keywords that are specifically designed to help the programmer to squeeze more performance out of a numerical routine. C++ has this too, but not to the extent Fortran does.

Another advantage is that Fortran is not operating system or architecture specific. In other words the Fortran code you write on one operating system or architecture should easily port to another where there is a Fortran compiler.

Another advantage is that modern Fortran is normally backwards compatible with older code bases of Fortran. And the code base that has been built over the years in Fortran is huge and extremely sophisticated (being mostly done by scientists and mathematicians).

Also, personally, I really enjoyed the built-in file handling functions that allow one to read a data file and perform operations on it almost instantly. Many other built-in functions in Fortran are designed to allow this convenience. C++ offers mainly building blocks to do this and this requires a bit of sweating it out just to read a data file b/c you need to know something about delimiters (where Fortran allows you to specify the delimiter).

Beyond this I can't think of advantages. Most anything else would be string manipulations, or algorithmic based operations to which c++ as a language, and in general it's compilers, are better suited and most often will perform better. A good knowledgeable programmer will likely prefer c++ as she/he would understand how to optimize a numerical routine in a way that could likely perform better than a Fortran compiled routine. Additionally good reliable Fortran compilers are not as easy to come by as good reliable C++ compilers.

IMHO, the only advantage that really matters is that programming FORTRAN allows you easier reuse of a lot of existing FORTRAN code and libraries. And if you have 50 FORTRAN programmers at hand for a project and a limited time frame, are you going first to teach them all C++, or will you accept to let them use their favorite language?

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.

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.