in Sources/_TracingBenchmarkTools/DriverUtils.swift [669:675]
func quantiles(q: Int) -> [Int] {
let qs = (0 ... q).map { i in r[Double(i) / Double(q)] }
return c.delta ?
qs.reduce(into: (encoded: [], last: 0)) {
$0.encoded.append($1 - $0.last); $0.last = $1
}.encoded : qs
}