With:
let nbrBytes = 400_000_000
let localArray = UnsafeMutablePointer<UInt8>.allocate(capacity: nbrBytes)
// touch every page before summing:
for i in 0 ..< nbrBytes / 4096 { localArray[ 4096 * i ] = 1 }
This rather innocent loop:
var count: UInt64 = 0
for index in 0 ..< loopLimit { count += UInt64( localArray[ Int(index) ] ) }
takes 2.4 times as long if preceded by:
let loopLimit = UInt64(nbrBytes)
compared to:
let loopLimit = Int(nbrBytes)
Why can’t Swift iterate in UInt64 as efficient as with Int?
Any real issue here which I am overlooking or just a compiler bug?
Gerriet.
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