https://stackoverflow.com/q/66515194/1271826

ThreadExplosion.swift

// The following results in thread explosion:

for idx in 0..<10_000 {
    concurrentQueue.async(group: group) {
        self.something.n += idx
    }
}

// We would instead do

concurrentQueue.async {
    DispatchQueue.concurrentPerform(iterations: 10_000) { idx in
        self.something.n += idx
    }
}

By using concurrentPerform, the number of GCD worker threads is limited to the number of cores on the device.

Needless to say, this isn’t thread-safe operation. I’m just showing how to avoid thread issue explosion.