script_runner.lua

--   Usecase for a script runner.
--   Author: Pushpendre Rastogi
--   Date: 8 July 2017
-- Multiple small changes in code are a norm when developing machine learning software
-- in dynamic languages, such as lua, python, because of a large number of hyper-parameters
-- in machine learning code, and large number of typos because of lack of compile time
-- type checking. For example, lua does not even enforce the number of arguments to a
-- function to be the same as its signature. Because of this ML code typically needs to be
-- run multiple times during development with small changes/fixes.
-- ML code also commonly has costly processing that must be done on a dataset.
-- For reasons of performance / simplicity often such preprocessing is done in a
-- batch manner instead of an online manner through iterators.
-- Often time the datasets are so large that even serializing/deserializing
-- the processed datasets can take a large amount of time.
-- This combination of large number of restarts, with each restart having a large fixed
-- startup cost causes a lot of difficulty for developers.
--
-- A script runner is basically eval-loop that keeps time-consuming data structures
-- in memory, but it reloads the code/script that must be run each time. Finally,
-- it also allows incremental changes to hyper-parameters between the run of a script
-- by reading the user's input.
--
-- The following is a script runner written in `lua`
-- The `torch.CmdLine` library is used for command line processing.
-- USAGE: lua script_runner.lua  -arg 2
--[[ script.lua
  function p()  print(opt.arg) end p()
--]]
cmd = torch.CmdLine()
cmd:text()
cmd:option('-arg', 1,'')
cmd:text()
cmd:text('Options')
opt = cmd:parse(arg)


while true do
  local r, errmsg = pcall(dofile, 'tmp3.lua')
  if(not r) then print('ERROR: ' .. errmsg) end

  io.write('Continue? (C-q C-c to exit, edit cmdline by typing here) ')
  v = io.read("*l")
  if v ~= "" then
    local input = {}
    local i = 0
    for e in string.gmatch(v, "([^ ]+) *") do
      i = i + 1
      input[i] = e
    end
    opt2 = cmd:parse(input)
    for a,b in string.gmatch(v, "-+([^ ]+) *([^ ]+) *") do
      print('Updated GLOBAL_OPT[' .. a .. '] = ' .. opt2[a])
      opt[a] = opt2[a]
    end
  end
end

good