Is a program F# any more efficient (execution-wise) than C#?

Question

I'm guessing that it is not because they both boil down to the same IL

Answer 1

It will depend. The sort of solutions you will create in F# will often have a very different form to those in C#. It is not uncommon in Functional language code solutions to trade some speed for clarity and succintness.

Answer 2

You can probably write code in either language that will compile to almost exactly the same CLR bytecode.

The important question is whether idiomatic F# will be more efficient than idiomatic C#.

For example, functional programming languages tend to favor use of immutable datastructures (some, but not F#, even require it). While these datastructures can be made more efficient than their naive implementations (which would involve a lot of cloning), mutable datastructures inherently give more freedom to the programmer, and can therefore be more efficient.

That being said, there is a theoretical argument that immutability is better suited to exploiting multi-core processors and parallelism in general. I'm not aware of any actual research that proves this though.

The bottom line is that there is no simple answer, but generally well-written F# will probably be slower because it places a higher priority on adherence to functional programming ideology, which prioritizes elegance at the expense of efficiency.

Answer 3

I would say that it depends on what "effectiveness" are we talking about. I think that in most cases the final code (IL) is going to be very similar. On the other hand the effectiveness of you, as a developer, might be different. There are certain problems that are more easily described and implemented using a functional language and in those cases the code will be more easily written and maintained using a functional language.

I personally see the power of F# in the fact that because it is built on top of CLR you can mix F# and C# to describe different parts of your applications in different language (you use the one that is more suitable).

PS: The same is true for dynamic languages. I don't think that they are that much better than languages like C# but for certain type of programming you might feel more productive.

Answer 4

For a wide range of programs, similar code in the two languages should exhibit similar performance characteristics; it's a goal for F# to have similar perf on like-to-like code comparisons. Simply transliterating code from C# to F# or vice-versa should have almost no effect.

As mentioned by others, some F# data structures and idioms can trade away some perf for other benefits. But it's your choice; F# perfomance methodology embraces imperative programming when it will net you measurable benefits, so if you need to use lots of arrays and for-loops, go for it.

F# does offer a great deal for high-performance computing, notably language features like async workflows (which make it easy to parallelize code or take advantage of multiple CPUs) and a general preference for immutability (which can make multi-threaded code less error-prone).

Finally, though a little outside the scope of the question (which asks for a comparison between the two), don't forget that in the real world you don't always have to choose one or the other. A number of apps have been written with a mix of F# and C#; interop between the two languages is very simple and straightforward, and it often makes sense to author a portion of a large app in one language and another portion in the other, to take advantages of their relative strengths.

Answer 5

I would assume the same... Maybe the syntax translates to few more instructions, but it will be negligible...

RWendi

Answer 6

Not right now but certainly F# will perform much faster than C# in some domains later on. The reason is that F# forces you to write code in declarative manner and use immutable types. This is very important because JIT compiler (after some adjustments to it) will be able to utilize multi-core CPUs automatically.

There is also possibility that F# will never become mainstream and somehow C# will inherit F# features in following years making good old C# a new F#.

Answer 7

F# provides some performance-related features that can make a difference.

Firstly, the implementation of delegates on .NET is currently quite inefficient and, consequently, F# uses its own FastFunc type for high-performance first-class functions.

Secondly, F# uses .NET metadata to convey inline functions so that they can be exported across APIs and, of course, that can dramatically improve performance in certain circumstances. Moreover, F#'s inlining allows functions passed as arguments to higher-order functions to be completely inlined and type specialized. Our F# for Numerics library makes extensive use of this feature to ensure that per-type functions such as comparison are specialized, giving performance in F# up to 2,350x faster than the equivalent C# (!). In fact, some of our numerical routines are consistently several times faster than vendor-tuned Fortran in libraries like the Intel MKL.

Finally, pattern matching can be extremely laborious to express in C# because the language lacks pattern matching but it is almost impossible to maintain optimized C# code equivalent to many non-trivial pattern matches. In contrast, the F# compiler aggressively optimizes pattern matches during compilation.

Conversely, the C# compiler may still be better at optimizing computations over value types (e.g. complex arithmetic) and has "goto" which can be more efficient than anything currently available in F#.

Cheers, Jon Harrop.