[Freeciv-Dev] Re: (PR#576) Wishlist: alternating unit movement

["Jason Short" <jdorje@xxxxxxxxxxxxxxxxxxxxx>]

<URL: http://rt.freeciv.org/Ticket/Display.html?id=576 >

A not on spaceships.

Launching a spaceship is an action; you should only be able to do this 
on your phase.  There are some problems with spaceships if they're done 
wrong.

Suppose you have 5 players, numbered 0-4 and taking their phases in 
order.  Now...

One possibility is that you check for spaceship arrival for everyone at 
the beginning of the *turn*.  However this is quite bad.  Say player 4 
launches their spaceship in 1900 with a travel time of 1.0 years.  Now 
it will arrive immediately at the start of 1901; the other players never 
had a chance to counter-attack.  By comparison if player 0 launches in 
1900 everyone will have a chance to counter-attack.

So obviously the phase has to play some role.  There are two ways this 
could be better done...but each has problems of its own.

In one method, each phase (in the above example) lasts 0.2 years. 
Remember that spaceships may take a non-integer number of years to 
arrive.  So if player 4 launches their 1.0-year spaceship in the year 
1900.8 (their phase), it doesn't arrive until 1901.8 (their phase in 
1901).  This is better.  However there is still a problem: suppose 
player 1 launches a 1.5-year spaceship and player 4 launches a 1.2-year 
spaceship, both in 1900.  Now player 1's spaceship arrives at 1901.7 and 
player 4's spaceship arrives in 1902.0.  So player 1 wins just because 
they happened to go first, which is obviously bad.  Also its a bit bad 
to have spaceships arriving at random points during the turn 
(complicated for the player to figure out when it will arrive) - note 
that in the second example above player 1 wins the game at the start of 
player 3's phase in 1901.

In the other method you do spaceship checking at the beginning of the 
phase but only for the active player.  Any fraction part of a year is 
simply left out in this case.  So when player 4 launches their 1.0-year 
spaceship in 1900 (launched during their phase, of course) it will 
arrive at the beginning of their phase in 1901 - the same as above. 
However in the second example player 1's 1.5-year spaceship will arrive 
at the beginning of player 1's phase in 1901, and player 4's 1.2-year 
spaceship at the beginning of player 2's phase in 1902.  So again player 
1 wins just because they happen to be shuffled first.  But at least now 
it's obvious to the players when the spaceship is going to arrive.

jason