View difference between Paste ID: wfM7cXtU and nWC9sNex

 function test_tableremove(mylist)
     for i=#mylist,1,-1 do
         if mylist[i] == 13 then
             table.remove(mylist, i)
         end
     end
 end -- func
 
 function test_mitch(mylist)
     -- NOTE: This is a messy, hardcoded version of my algorithm, for test-purposes.
     -- Go to https://stackoverflow.com/a/53038524/8874388 for the actual, clean version.
     local j, n = 1, #mylist;
 
     for i=1,n do
         local value = mylist[i]
         if value ~= 13 then -- Keep everything except "13"
             -- Move i's kept value to j's position, if it's not already there.
             if (i ~= j) then
                 mylist[j] = mylist[i];
                 mylist[i] = nil;
             end
             j = j + 1; -- Increment position of where we'll place the next kept value.
         else -- Delete "13"
             mylist[i] = nil;
         end
     end
 end
 
 function build_tables(howMany)
     local ofs = {}
     for i=1,howMany do
         ofs[i*50] = true;
     end
 
     local tables = {}
     for i=1, 1 do
       tables[i] = {}
       for j=1, 2000000 do -- 2 million items
         tables[i][j] = (ofs[j] and 13 or 100) -- put a "13" (deleted) in the slots to be deleted, otherwise "100" (kept)
       end
     end
 
     return tables
 end
 
 function time_func(func, name, howMany)
     local tables = build_tables(howMany)
     time0 = os.clock()
     for i=1, #tables do
         func(tables[i])
     end
     time1 = os.clock()
     print(string.format("[%13s] elapsed time (deleting %.0f items): %.3f\n", name, howMany, time1 - time0))
 end
 
 -- The number below (i) controls how many items that will need to be deleted from the array.
 -- This test checks if table.remove() is ever faster if you only need to remove a few entries.
 -- The test arrays contain 2 million items, and the items that need to be removed at all at the start,
 -- hence triggering the need to re-index the subsequent array entries.
 for i=1,6 do
     time_func(test_mitch, "mitch", i)
     time_func(test_tableremove, "table.remove", i)
 end
 
 
 --[[
 
 LuaJIT 2.0.5 -- Copyright (C) 2005-2017 Mike Pall. http://luajit.org/
 JIT: ON CMOV SSE2 SSE3 SSE4.1 fold cse dce fwd dse narrow loop abc sink fuse
 
-[        mitch] elapsed time (deleting 1 items): 0.011
+[        mitch] elapsed time (deleting 1 items): 0.008
 
-[ table.remove] elapsed time (deleting 1 items): 0.011
+[ table.remove] elapsed time (deleting 1 items): 0.010
 
-[        mitch] elapsed time (deleting 2 items): 0.009
+[        mitch] elapsed time (deleting 2 items): 0.008
 
-[ table.remove] elapsed time (deleting 2 items): 0.014
+[ table.remove] elapsed time (deleting 2 items): 0.019
 
 [        mitch] elapsed time (deleting 3 items): 0.008
 
 [ table.remove] elapsed time (deleting 3 items): 0.022
 
-[        mitch] elapsed time (deleting 4 items): 0.010
+[        mitch] elapsed time (deleting 4 items): 0.008
 
 [ table.remove] elapsed time (deleting 4 items): 0.028
 
 [        mitch] elapsed time (deleting 5 items): 0.008
 
 [ table.remove] elapsed time (deleting 5 items): 0.031
 
 [        mitch] elapsed time (deleting 6 items): 0.008
 
 [ table.remove] elapsed time (deleting 6 items): 0.039
 
 
 
 Lua 5.3.4  Copyright (C) 1994-2017 Lua.org, PUC-Rio
 
 + $ lua test.lua
 [        mitch] elapsed time (deleting 1 items): 0.306
 
 [ table.remove] elapsed time (deleting 1 items): 0.121
 
 [        mitch] elapsed time (deleting 2 items): 0.309
 
 [ table.remove] elapsed time (deleting 2 items): 0.164
 
 [        mitch] elapsed time (deleting 3 items): 0.313
 
 [ table.remove] elapsed time (deleting 3 items): 0.237
 
 [        mitch] elapsed time (deleting 4 items): 0.326
 
 [ table.remove] elapsed time (deleting 4 items): 0.262
 
 [        mitch] elapsed time (deleting 5 items): 0.326
 
 [ table.remove] elapsed time (deleting 5 items): 0.304
 
 [        mitch] elapsed time (deleting 6 items): 0.334
 
 [ table.remove] elapsed time (deleting 6 items): 0.341
 
 
 
 ]]--