Improve minResolution

src/resolution.js

@@ -10,22 +10,42 @@ export const getTimeResolution = function() {
   )
 }
 
-// Run `now()` several times in a row
+// Run `now()` several times in a row.
+// We do it several times because there is a chance that the next resolution
+// would be hit otherwise. For example:
+//  - if resolution is 1ns, samples might (by chance) all be modulo 5ns
+//  - if resolution is 5ns, samples might (by chance) all be modulo 10ns
+// The probability for this to happen is:
+//  - if resolution is *1ns, `1 / 5 ** length`
+//  - if resolution is *5ns, `1 / 2 ** length`
+// So with `length` `100`, we get this error only once every `1e30` calls.
+// We must use imperative code because the loop size is unknown.
+/* eslint-disable fp/no-let, fp/no-loops, fp/no-mutation, fp/no-mutating-methods,
+max-depth */
 const getTimes = function(length) {
-  const times = Array.from({ length }, now)
-  const uniqueTimes = [...new Set(times)]
-  return uniqueTimes
+  const times = []
+  let lastTime = 0
+
+  while (times.length < length) {
+    const time = now()
+
+    // If the resolution is very low, we need to perform `now()` several times
+    // until the result changes
+    if (time !== lastTime) {
+      lastTime = time
+      times.push(time)
+    }
+  }
+
+  return times
 }
+/* eslint-enable fp/no-let, fp/no-loops, fp/no-mutation, fp/no-mutating-methods,
+max-depth */
 
 const REPEAT = 1e2
 
 // Check among all `now()` if they fit a specific time resolution
 const isTimeResolution = function(resolution, times) {
-  // Performance optimization. Avoid looping over every `times`
-  if (resolution === MIN_RESOLUTION) {
-    return true
-  }
-
   return times.every(time => time % resolution === 0)
 }
 
@@ -51,6 +71,3 @@ const getPossibleResolution = function(exponent) {
 }
 
 const POSSIBLE_RESOLUTIONS = getPossibleResolutions()
-
-// 1 nanosecond
-const MIN_RESOLUTION = POSSIBLE_RESOLUTIONS[POSSIBLE_RESOLUTIONS.length - 1]