Fast Filter for F#

fastFilter.fs

// Faster than the core lib filter in most scenarios.
// Core lib may be faster when filtering about half the data
// and the filtered data is randomy distributed in the array.
// Even in cases where it is a little slower, it allocates a lot 
// less. Relieving GC overhead.
let inline filter (f: ^T -> bool) (array: ( ^T)[]) = 
    
    let len = array.Length
    if array = null then invalidArg "array" "Array can not be null."            
    if len = 0 then invalidArg "array" "Array can not be empty."    
        
    let mutable count = 0
    let temp = Array.zeroCreate len
    for i = 0 to array.Length-1 do        
        let b = f array.[i]        
        if b then
            temp.[i] <- b
            count <- count + 1
                    
    let result = Array.zeroCreate count
    let mutable j = 0    
    for i = 0 to array.Length-1 do
        if temp.[i] then
            result.[j] <- array.[i]
            j <- j + 1
    result