From 199d6c190882e2e279539a0649d7be104cb2e15a Mon Sep 17 00:00:00 2001
From: Stefan Harmuth <pennywise@drock.de>
Date: Sat, 19 Nov 2022 12:57:40 +0100
Subject: [PATCH] more precise stopwatch

---
 tools/stopwatch.py | 46 +++++++++++++++++++++++++++-------------------
 1 file changed, 27 insertions(+), 19 deletions(-)

diff --git a/tools/stopwatch.py b/tools/stopwatch.py
index 1c520a0..ce2fcea 100644
--- a/tools/stopwatch.py
+++ b/tools/stopwatch.py
@@ -1,43 +1,51 @@
-from time import time
-from .types import FloatOrNone
+from time import perf_counter_ns
+from .types import IntOrNone
+
+
+def ns_to_string(ns: int) -> str:
+    units = ['ns', 'µs', 'ms', 's']
+    unit = 0
+    while ns > 1_000:
+        ns /= 1_000
+        unit += 1
+        if unit == len(units) - 1:
+            break
+
+    return f"{ns:1.2f}{units[unit]}"
 
 
 class StopWatch:
-    started: FloatOrNone = None
-    stopped: FloatOrNone = None
+    started: IntOrNone = None
+    stopped: IntOrNone = None
 
     def __init__(self, auto_start=True):
         if auto_start:
             self.start()
 
     def start(self):
-        self.started = time()
+        self.started = perf_counter_ns()
         self.stopped = None
 
-    def stop(self) -> float:
-        self.stopped = time()
+    def stop(self) -> int:
+        self.stopped = perf_counter_ns()
         return self.elapsed()
 
     reset = start
 
-    def elapsed(self) -> float:
+    def elapsed(self) -> int:
         if self.stopped is None:
-            return time() - self.started
+            return perf_counter_ns() - self.started
         else:
             return self.stopped - self.started
 
-    def avg_elapsed(self, divider: int) -> float:
-        return self.elapsed() / divider
+    def avg_elapsed(self, divider: int) -> int:
+        return self.elapsed() // divider  # in ns precision loosing some rounding error probably will not hurt
+
+    def elapsed_string(self):
+        return ns_to_string(self.elapsed())
 
     def avg_string(self, divider: int) -> str:
-        units = ['s', 'ms', 'µs', 'ns']
-        unit = 0
-        elapsed = self.avg_elapsed(divider)
-        while 0 < elapsed < 1:
-            elapsed *= 1000
-            unit += 1
-
-        return "%1.2f%s" % (elapsed, units[unit])
+        return ns_to_string(self.avg_elapsed(divider))
 
     def __str__(self):
         return self.avg_string(1)