From caf556e2dcb3df4992dd386a2b37535df42fc880 Mon Sep 17 00:00:00 2001
From: Benoit Germain <benoit.germain@ubisoft.com>
Date: Wed, 27 Mar 2024 17:02:37 +0100
Subject: updated perftest.lua

---
 tests/perftest.lua | 74 +++++++++++++++++++++++++++++++-----------------------
 1 file changed, 42 insertions(+), 32 deletions(-)

diff --git a/tests/perftest.lua b/tests/perftest.lua
index 6ffc064..35f522c 100644
--- a/tests/perftest.lua
+++ b/tests/perftest.lua
@@ -83,46 +83,53 @@ PRIO_EVEN= PRIO_EVEN or 0
 --
 -- AKa 20-Jul-2008: Now the wrapping to one function is no longer needed;
 --     Lanes 2008 can take the used functions as upvalues.
---
+
+-- It looks like this implementation uses a lot of C stack, possibly resulting in stack overflow with Lua54
+-- this is reproducible with the original sieve.lua implementation found at https://www.lua.org/extras/
+-- for example: 
+-- Lua54 exe built with 1Mb of C stack crashes for M above 230, C stack at 500 calls
+-- Lua53 exe built with 1Mb of C stack crashes for M above 491, C stack at 740 calls
+-- Lua52 exe built with 1Mb of C stack crashes for M above 672, C stack at 1000 calls
+-- Lua51 exe built with 1Mb of C stack crashes for M above 718, C stack at 900 calls
 local function sieve_lane(N,id)
 
- if MSYS then
-   io.stderr:setvbuf "no"
- end
+    if MSYS then
+        io.stderr:setvbuf "no"
+    end
+
+    -- generate all the numbers from 2 to n
+    local function gen (n)
+        return coroutine.wrap(function ()
+            for i=2,n do coroutine.yield(i) end
+        end)
+    end
 
- -- generate all the numbers from 2 to n
- local function gen (n)
-  return coroutine.wrap(function ()
-    for i=2,n do coroutine.yield(i) end
-  end)
- end
+    -- filter the numbers generated by `g', removing multiples of `p'
+    local function filter (p, g)
+        return coroutine.wrap(function ()
+            while 1 do
+                local n = g()
+                if n == nil then return end
+                if math.fmod(n, p) ~= 0 then coroutine.yield(n) end
+            end
+        end)
+    end
 
- -- filter the numbers generated by `g', removing multiples of `p'
- local function filter (p, g)
-  return coroutine.wrap(function ()
+    local ret= {}      -- returned values: { 2, 3, 5, 7, 11, ... }
+    N=N or 1000	    -- from caller
+    local x = gen(N)   -- generate primes up to N
     while 1 do
-      local n = g()
-      if n == nil then return end
-      if math.fmod(n, p) ~= 0 then coroutine.yield(n) end
+        local n = x()		-- pick a number until done
+        if n == nil then break end
+        --print(n)		-- must be a prime number
+        table.insert( ret, n )
+
+        x = filter(n, x)	-- now remove its multiples
     end
-  end)
- end
-
- local ret= {}      -- returned values: { 2, 3, 5, 7, 11, ... }
- N=N or 1000	    -- from caller
- local x = gen(N)   -- generate primes up to N
- while 1 do
-  local n = x()		-- pick a number until done
-  if n == nil then break end
-  --print(n)		-- must be a prime number
-  table.insert( ret, n )
-
-  x = filter(n, x)	-- now remove its multiples
- end
  
- io.stderr:write(id..(MSYS and "\n" or "\t"))   -- mark we're ready
+    io.stderr:write(id..(MSYS and "\n" or "\t"))   -- mark we're ready
 
- return ret     
+    return ret
 end
 -- ** END OF LANE ** --
 
@@ -169,6 +176,7 @@ else
     --
     for i=1,N do
         local tmp= t[i]:join()
+        -- this assert will trigger if you change M to values below 1000 in order to solve C stack overflow
         assert( type(tmp)=="table" and tmp[1]==2 and tmp[168]==997 )
     end
 end
@@ -180,5 +188,7 @@ if TIME then
     io.stderr:write( "*** TIMING: "..t.." seconds ***\n" )
 end
 
+io.stderr:write "done\n"
+
 --
 -- end
-- 
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