benchmark func name generation.lua

--[[
-------

My messy benchmarking file for debug.getinfo vs jit.util.funcinfo

I found, that funcinfo cannot beat the speed of debug.getinfo - because jit.util.funcinfo needs
a reference to the calling function which requires a debug.getinfo call itself.

I managed to get the speed down to these sats as the file stands:

test_1 (debug.info) took: -- AppleCake 2.1 solution
 Avg: 0.00049ms
 Worse: 0.01820ms
 Best: 0.00030ms
---
test_2 (jit.util) took:
 Avg: 0.00077ms
 Worse: 0.01870ms
 Best: 0.00050ms
---
test_3 (fast?) took:
 Avg: 0.00057ms
 Worse: 0.01860ms
 Best: 0.00030ms
---
test_4 (final solution) took:
 Avg: 0.00045ms
 Worse: 0.01280ms
 Best: 0.00030ms

-- Note, if you add :gsub(":", "@") into fast_name, it bumps `best` to 0.00040ms, not worth it for styling
-------
]]--


local jit_util = require("jit.util")

local old_name = function()
  local info = debug.getinfo(2, "fnS")
  local name
  if info.name then
    name = info.name
  elseif info.func then -- Attempt to create a name from memory address
    name = tostring(info.func):sub(10)
  else
    error("Could not generate name for this function")
  end
  if info.short_src then
    name = name.."@"..info.short_src..(info.linedefined and "#"..info.linedefined or "")
  end
  return name
end

local new_name = function()
  local info = debug.getinfo(2, "fn")
  if info then
    local name
    if info.name then
      name = info.name
    elseif info.func then
      name = tostring(info.func):sub(10)
    else
      error("Could not generate name for this function")
    end

    if info.func then
      local j_info = jit_util.funcinfo(info.func)
      if j_info and j_info.source then
        local short_src = j_info.source
        local prefix = short_src:sub(1, 1)
        if prefix == "@" or prefix == "=" then
          short_src = short_src:sub(2)
        else
          short_src = '[string "' .. short_src:sub(1, 40) .. '..."]'
        end

        name = name .. "@" .. short_src .. (j_info.linedefined and "#" .. j_info.linedefined or "")
      end
    end
    return name
  end
end

local fast_name = function() -- The two C calls is the issue, 
  local info = debug.getinfo(2, "f")
  if not info then return "unknown" end

  local j_info = jit_util.funcinfo(info.func)
  -- local name = info.name or tostring(info.func):sub(10)
  local name

  if j_info and j_info.source then
    -- local src = j_info.source
    -- local prefix = src:sub(1, 1)
    -- if prefix == "@" or prefix == "=" then
    --   src = src:sub(2)
    -- end
    -- name = name .. "@" .. src .. (j_info.linedefined and "#" .. j_info.linedefined or "")
    -- name = name .. "@" .. src .. "#" .. j_info.linedefined
    name = j_info.loc--:gsub(":", "@")
    -- print(name)
    -- name = ("%s@%s"):format(name, src)
  end
  return name
end

local generateFuncName = function()
  local info = debug.getinfo(3, "fnS")
  local name = info.name or tostring(info.func):sub(10)
  if info.short_src then
    name = name .. "@" .. info.short_src
  end
  if info.linedefined then
    name = name .. "#" .. info.linedefined
  end
  return name
end

local _getTime = love.timer.getTime
local getTime = function() -- Time in microseconds
  return _getTime() * 1e+6
end

local benchmark = function(name, func, iterations)
  local total = 0
  local best = math.huge
  local worse = 0

  -- warmup
  for _ = 1, 100 do func() end

  for _ = 1, iterations do
    local s = getTime()
    func()
    local f = getTime()

    local d = f - s
    total = total + d
    if d < best then best = d end
    if d > worse then worse = d end
  end
  
  local avg = total / iterations
  print(("%s took:\n Avg: %.5fms\n Worse: %.5fms\n Best: %.5fms"):format(
    name, avg / 1000, worse / 1000, best / 1000
  ))
end


local n = 100000

local test_1 = function() return old_name() end
local test_2 = function() return new_name() end
local test_3 = function() return fast_name() end
local test_4 = function() return generateFuncName() end

benchmark("test_1 (debug.info)", test_1, n)
print("---")
benchmark("test_2 (jit.util)", test_2, n)
print("---")
benchmark("test_3 (fast?)", test_3, n)
print("---")
benchmark("test_4 (final solution)", test_4, n)