Zezo forum:

Post by TSIONA | 2009-06-07 | 05:31:48

There is a shift of one wind rectangles in comparison to VORG.

7 Comments

Post by zezo | 2009-06-07 | 10:38:19

Thanks. This question comes up all the time.

Both the game and the simulation are run in discrete steps.

So if you sail from the edge of a rectangle into the next one you will move with the old wind for 10 minutes. You can move few miles against the new wind.

The simulator uses 10-minute step for the 1-day prediction, so it's pretty close to the game, but the step increases for the longer periods, so it's better to use the 1-day tracks with manually set destination points.

The important thing is that the changes should be done before the announced time. The game does not care if you turn at 10:02 or 10:09, it sees is at 10:10. It's even more important for the 11 and 23h wind updates when you can gain or lose few miles in a single 10-minute step with the right conditions.

I could have added all that logic to the program, but have decided to leave some thinking for the players :)

Cvetan

Post by 63_Buri | 2009-06-07 | 19:01:26

@Cvetan
Are you certain that the change of course is for the next time interval?

I have just been navigating around Guernsey and it seems that the course change you make between, say, 17:50 (actually, for me, 17:52:30 - there is a delay as the server recalculates) and 18:00 takes effect for that interval (17:50 - 18:00). When my position is updated (at 18:02:30) the difference between that position and the last differs by the course I set between the two (say at 17:55).

Post by zezo | 2009-06-07 | 19:13:57

I have tried to say more or less the same thing, bit it was before the first coffee in the morning ;)

You are correct that the server takes somewhere between 1m30 and 2m30 to recalculate all boat positions, and it's not clear what happens if you change something in the first 2 minutes. Right now the most likely thing is that you get the 'sorry for the inconvenience' message ;)

The other difference is that you look at time as interval, and I see it as a step in discrete world.

The game server works like this: take the last known position, heading and speed and calculate the new position like gc_destination(last_pos, heading, speed/6).

Post by mpako | 2009-06-10 | 01:00:17

well, I just tried to change course radically before indicated time 23.45(in fact the boat stopped) but according to the above comments I assumed it will go to calc as 23.50.
no.
I was on the same place in next 10 mins lost 25 places.
next time I'll change after 10...

Post by zezo | 2009-06-10 | 01:06:31

That's how it's supposed to work, but we can not be sure about it. And the the game has synchronization issues sometimes, and you get stale data, and places and ranks is totally out of sync.

So it's up to you. Experiment, try different things and use whatever works best.

Post by mpako | 2009-06-10 | 01:12:22

OK, thanks.
as it was my second boat ranking around 4k... it's no prob.
but you are right - sometimes it works. maybe closer to end of period...

Post by Oceans_United | 2009-06-10 | 03:39:16

Hi
I have tested this very heavily during leg 6 and leg 7. I am 99.99% confident that zezo's explanation is correct.
I have tried almost everything. At all possible times during the 10 min. period. Even multiple changes within 10 min.
Conclusion: Only what is registered at the game server at regular 10 min. intervals. (00, 10, 20,...) is used. Doesn't matter if it was done at say 14:10:02 or 14:19:59 or at both instants. It will use whatever info is there at 14:20:00.
One important thing. The server seem to use the position and corresponding wind from 10. min back, that is at 14:10:00 in the example above.

To be a little more precise i think one second past as in 14:20:01 is the decisive moment. At least that is what is indicated in the attribute for the position tag in the xml-feed: <position date="2009-05-24 01:10:01"> and also in the travel time to finish when arrived: <temps_etape>628801</temps_etape> which is seconds since start of leg.

So as zezo says, think of the game as discrete blocks, where only ONE route calculation is done based upon what is know about the boat at the time of shift from one block to the next.