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A lot of array boundary checking slows down the speed, this is especially true to 2D arrays. Is there a way to write unsafe code blocks in F#?
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Remember: The notation "f (x)" is exactly the same thing as "y". You can even label the y-axis on your graphs with "f (x)", if you feel like it. Let me clarify another point. While parentheses have, up until now, always indicated multiplication, that is not the case with function notation.
f:x↦y means that f is a function which takes in a value x and gives out y.
more ... A special relationship where each input has a single output. It is often written as "f(x)" where x is the input value. Example: f(x) = x/2 ("f of x equals x divided by 2")
Given a function f, the derivative f' can be used to get important information about f. For instance, f is increasing when f'>0. The second derivative gives useful concavity information.
I'm not a F# programmer but as far as I can see it doesn't seem to have the unsafe keyword.
You could possibly get a performance boost by transforming the 2D array to an one-dimensional array.
Advice 5: Until we get this right, I would suggest that .NET users do what many C++ numerical programmers do: write a class to implement your n-dimensional array. This would be represented as a 1-dimensional array, and the relevant accessors would convert n indices into 1 via appropriate multiplications. We almost certainly wouldn’t eliminate the bounds check into the 1-d array, but at least we’d only do one check!
Array Bounds Check Elimination in the CLR
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See here for some ways to get the compiler to remove boundary checking for you. Basically, you need to write your loops in such a way that the compiler knows your indexes will be in bounds. If it knows it will be in bounds, then when you run in release mode without debugging, the JIT compiler will remove the bounds checks for you.
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