Throttle test execution when tests are too fast

Large number (hundreds and more) of extremely fast tests could block the
UI. To avoid that, measure how fast tests are. If they are too fast and
the number of tests is significant then slow them down by sleeping.

Author: elgopher

runner.lua

@@ -9,6 +9,7 @@
 -- runner send messages with events to communicate with the parent process.
 
 include "api.lua"
+include "throttler.lua"
 
 local work_dir            = env().path
 
@@ -24,9 +25,12 @@ end
 
 local id_sequence = 0
 
-local tests <const> = {} -- {id=1,name=..}
+local tests <const> = {}                            -- {id=1,name=..}
+
+local publish_throttler <const> = new_throttler(50) -- max 50 messages per frame
 
 local function publish(msg)
+	publish_throttler:throttle()
 	send_message(parent_pid, msg)
 end
 

throttler.lua

@@ -0,0 +1,32 @@
+-- (c) 2024 Jacek Olszak
+-- This code is licensed under MIT license (see LICENSE for details)
+
+-- creates an object which slows down the code if it runs too fast
+function new_throttler(max_per_frame)
+   local fps <const> = 60
+   local instructions_per_second = 8000000 -- max no of instructions in Picotron
+
+   local started, count
+
+   local function reset()
+      started = time()
+      count = 0
+   end
+
+   reset()
+
+   local throttler <const> = {}
+
+   function throttler:throttle()
+      count += 1
+      if count > max_per_frame and
+          count / (time() - started) / fps > max_per_frame
+      then
+         -- sleep for a frame
+         for i = 1, instructions_per_second / fps do end
+         reset()
+      end
+   end
+
+   return throttler
+end