Favorite way to store next loop state?

[parallax7d]

Lets say I have many components sharing state (a block of memory or a big table or whatever, it doesn't matter) and doing work to setup the values for the next loop. I don't know where to put these calculated values though.

Lets say all the data is stored in a big table called 'current'. I can't let my components do their work and write back to 'current' because other components (they all act independently) potentially need access to that original data for their own work.

Should I create a whole new table and let each component write their results to it? A table called 'next'? And each loop rename 'next' to 'current'?

Or should the 'current' data and 'next' data be written in the same table like [[xpos_1, xpos_2], [ypos_1, ypos_2]] and just have all functions know if they should be using field 1 or field 2 during this loop?

Just interested in the pros and cons of different methods you folks commonly use.

[undef]

I would use 2 tables and one reference that is changing:

Code: Select all

local table
local table1 = { a, b, c }
local table2 = { d, e, f }

local function doStuffWithTable( t ) -- call with table
<...>
end

local function updateState( tableNum )
    if tableNum == 1 then
        table = table1
    else
        table = table2
    end
end

That way you only switch out the table you are performing computations on.

[parallax7d]

I was thinking about that, but if the condition results change literally every frame, it ends up being option a roughly 50% of the time, and option b 50% of the time. Won't that royally screw up any sort of branch prediction the cpu is trying to do? Is there a way to toggle the tables without using a condition? How about changing the names of the tables right before the next frame, that way the components never know about the change, and no if is needed?

[undef]

Oh, I didn't understand that you wanted to change the state every frame...
In that case a counter would probably work.
Just increment a counter and use modulo to keep it in a certain range.
If you have only two states you would do something like if counter%2==0 then else end.

Switching out tables and functions is useful if you go from the main menu into the game, or from the game to the pause menu or something.

[Robin]

Won't that royally screw up any sort of branch prediction the cpu is trying to do?

That line of thinking seems to me like a massive case of premature optimization.