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Name	dtayls
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2014-11-19 01:38:23

Re: Performance loss

Board » Technical Discussion

There are some really interesting ideas in the pipeline and there is a great team of people working on it. Physical (kinetic) performance loss certainly exists but it's probably not a significant issue in an ocean race. Crew fatigue, on the other hand, is probably much more important. Lots of manoevres (tacks/gybes) will take a big toll on the crew. And doing these in high winds or at night is going to have an even greater impact. So, perhaps double at night; a sliding scale from x1 to x5 from 20 to 50 kts; and a no-go-zone from 50kts+ where you can't tack or gybe at all because the crew is simply refusing to get up on deck.

--- Last Edited by dtayls at 2014-11-19 01:56:30 ---
2014-11-13 22:59:43

Re: Performance loss

Board » Technical Discussion

kroppyer: I think it is fair to say that the whole SOL community is indebted to you for your indepth investigations and analyses, not to mentionion the fact that you share this knowledge so openly. Your analysis of the whole performance model question is invaluable.

I can see what you are saying re 'dents' in the polars. The upwind and downwind ones are obviously the most obvious but there are others and yes these often relate to sail changes. I think it is clear that tacks and gybes should incur a performance penalty, but I personally think SOLers should be allowed to play with the other bumps and lumps to their hearts' content. As far as I can see any gains in actively playing these would be negligible so we'd might as well take the opportunity to simplify the SOL model by removing the dTWA dependency entirely.

If anything, maybe turning across a 'dent' should drop your speed to (say) half the depth of the dent. Thereafter it would be up to my generic exponential recovery model for boat speed to return to that indicated by the polar. This would work well for tacks and gybes too delivering a a 50% drop during a tack! During a gybe things would be a little different. A square-rigger, for instance, would see almost no penalty. A VO70 on the other hand would see perhaps a 15% hit, but they can immediately turn to a wind angle that gives them high AWS thus helping them recover any lost speed very quickly before settling at their optimum TWA.

Interestingly, while my model is very simple, it potentially encourages IRL sailing skills such as those involved with efficient tacking. Let's say our optimal upwind TWA is 45 degrees. During a tack we lose a bit of speed so we generally lay off a little by going past the optimal angle to say 50 degrees or maybe a little more. As we pick up speed we harden up to the optimal 45 degrees again.
2014-11-13 22:01:43

Re: Performance loss

Board » Technical Discussion

karriv: I love the technology of routers. As an electrical engineer and a computer scientist I just can't help myself. My ideal today would be using Expedition plugged in to SOL via BrainAid's NMEA plugin, then taking the steering data from Expedition and automatically feeding that back in to SOL.

The problem I have with what you are doing with (say) 200 DCs every 6 hours (ie. one DC every 1.8 mins) is that it either involves an autopilot or a very patient helmsman. In my experience, giving a helmsman a tiny change every couple of minutes is a good way of getting turned into a man-overboard dummy. And from that moment he/she is is going to follow your last instruction to the letter, so don't expect to be recovered from the water any time soon!

To be honest, I think it's great that people like you, kroppyer and others are willing to put in so much effort to developing and learning how to use advanced tools. The ultimate gift is then sharing this knowledge with others.
2014-11-13 13:48:44

Re: Performance loss

Board » Technical Discussion

Thanks kroppyer. I truly think that apparent wind (AWS) is a relevant driver for any meaningful performance model, particularly for the 'recovery' phase.

It think it's clear that we disagree on the question of penalties for non-tacking course-change manouevres. In reality, most sail changes occur when we go around marks where we change from up-wind to down-wind or vice-versa. Other than that, sail changes usually occur due to changes in the sailing environment - wind strength or direction changes - rather than as a change directed by the navigator (or SOLer, in our case). Of course, these can't be easily incorporated in to SOL because (a) our polars aren't sail-combo-specific and (b) that would be way too complex for most folk anyway!

You mention "polar hopping" as an issue but I don't quite get it. As far as I can see the current system not only supports but encourages small automated changes as these incur virtually no penalty. Systems that do this have many names but I simply call them 'autopilots'. And while I like playing with such technologies, I don't really want to race against them.

As a sailor I want something close to real-life. Realism is good, but this is a game after all so I'm happy to compromise a bit.

As an engineer I just want to create a model that makes sense ... to me, to sailors, and to novices alike.

As a programmer I want something I can implement cleanly and easily that will not suck the life out of the server platform through unnecessary calculations.

The 'performance model' (loss and recovery) has clearly been an issue for many years now. I personally think the time has come to tackle it and resolve it once-and-for-all.

There are two main forum threads dealing with this issue. If there are related thoughts/ideas/etc that have been shared only in emails then perhaps they should be shared here as well.

BTW. I am likely to go ferral on this issue if we don't get some traction ...
2014-11-13 01:43:21

Re: Performance loss

Board » Technical Discussion

It has been talked about for years, but I think the time for an update to the 'performance' model has finally arrived. The following is my summary and the beginnings of a proposal.

I have just re-read this thread (Performance loss) as well as the original 2008 Wrong Speed VMG topic. For anyone interested in the topic I would recommend reading both in full. The original 2008 topic gave some interesting insights in to the thinking behind the original PL approach adopted, but both then and now there are some major frustrations amongst both new and old SOLers with the model and how it works.

The original purpose was apparently to stop certain behaviours that were (presumably) causing undue load on the server or other problems. Back in 2009 jacob wrote the following:

jakob said @ 2009-02-12 10:36:39:

We introduced this performance loss not to punish normal sailing maneouvers but to prevent boats to tack e.g. once every minute during hours just to ride on a tws that optimizes vmg. The prformance loss implementation succeeded in preventing that behavior and is as stated above not a problem for normal maneouvers.))

BUT, with modern yachts - some of which can do in excess of 40kts - this model has clearly outlived its useful life and become a liability. It also penalizes newbies unnecessarily for simple learning mistakes.

Now, there have been a lot of good ideas proposed including momentum-based models, etc but I really think we need to keep it simple for a couple of reasons. Firstly, the model needs to be intuitive. It should make sense to IRL sailors as well as those new to SOL and to sailing in general. Secondly, it needs to be fair. It should not require intimate knowledge of the internals of the model - which I know and refuse to use - to sail a reasonable race. And thirdly, it should be easy to implement and relatively light on the server end. This one probably won't be so obvious to those without a computer science or engineering background, but it turns out that while linear responses are easy to graph and to understand, exponential responses - the way a lot of the natural world works - are actually really easy to do in 'discrete simulations' (eg. computer simulations such as SOL where everything moves in steps of say 15 seconds).

The basics of my proposal are as follows:

1. Scrap the per-degree PL penalty entirely. There is no basis in reality and I think no value in SOL. Also, newbies need to be able to play with direction changes. Of course, those effectively using autopilots (ie. large numbers of DCs) are another matter entirely and should simply declare their hand for all to see.

2. The 93% limit is a joke and needs to be scrapped. There is no basis for it and it is badly implemented. For instance, today I got down to 80% whereas if I had 'gamed it' then I would have never gone below 93%. This moves the focus from sailing to the gaming engine in which case EVERYONE loses.

Ok. That's two of the pillars of the current model discarded, so what's left?

Tacks and gybes clearly have performance impacts IRL and these need to be reflected in the SOL gaming engine. A yacht can almost stop in a tack but recovery is relatively quick whereas there is often little speed loss during a gybe but recovering any lost speed can take a very long time.

Looking at this from an engineering perspective, apparent wind strength (AWS) seems to be a very important factor here and it may be something that can be used to drive the 'recovery model'. Consider that before, during and after a tack the AWS is higher than it is for a gybe. What's more, in the seconds and minutes after a tack the AWS increases as the boat speed picks up thus increasing the driving/accelerating force, whereas, in the case of a gybe, as boat speed increases the AWS goes down and the accelerating force decreases meaning that it will take longer and longer to reach that theoretical max downwind speed for a given angle.

I propose (arbitrary) penalties of 25% for a tack and 10% for a gybe.

'Recovery' is then a different a matter. It should probably apply to ANY course change. At the time of any course change we know (a) the current boat speed which may of course be less than optimal (b) the theoretical boat speed on the new course according to the polar of the yacht and (c) the apparent wind speed (AWS). Given the appropriate combination of all three of these I think we should be able to develop a model for 'recovery' (or should we call it acceleration?) that makes sense to everyone. BTW, a change to a point of sail on the polar that indicates a lower theoretical speed than current should be immediate. The 'recovery model' should only be applied when a positive change in speed is indicated.

Should 'recovery' etc depend on the weight of the boat etc? Perhaps. Do we have this information today? No. Could we get this information? Yes. Where? I have some thoughts on this that I would be happy to share.

If we can get some agreement on these ideas then I will happily look at coding it ... with the agreement and assistance of hmmm and the SOL management team, of course.
2014-11-12 13:39:16

Re: Sailors with routers

Board » General Discussion

I propose we introduce three classes - novice, intermediate, and advanced - and that SOLers choose their class before the start of the race.

I have 40 years of real life yacht racing experience but in my first SOL race I was clearly a 'novice'. As an experienced ocean racer with a strong interest in navigation and tactics I soon saw myself as 'experienced' and simply wanted to race alongside the best ... even if I do keep getting beaten.

Depending on the level of past experience and weather/nav knowledge some may simply settle in at the novice or intermediate levels. And that is a perfectly reasonable place to be.

At the top level I think we may need to separate out those using a full 'autopilot' arrangement. But then again, IRL a good navigator/tactician can give instructions to the helmsman and crew covering the next six hours and that's going to be better than an autopilot anyway. Maybe copmetitors should be expected to carry a flag when the autopilot is engaged.
2014-11-10 05:17:56

Re: Sailors with routers

Board » General Discussion

To me, yacht racing is a little like golf. In golf we agree to be bound by the rules as we do when we race on the water (RRS #2 Fair Sailing).

I think we need to create two or three categories and people need to check the appropriate box at the beginning of the race and confirm it at the end ... a post-race declaration that we have sailed by the rules of the race.

Some possibilities include:

NR/SOTP - No Routing (nothing beyond the SOL client)
LR - Limited Routing (provided by SOL'ers)
FR - Free Router(s)
CR - Commercial Router (Expedition, etc)
AP - Full Auto-Pilot
X - eXperimental

Your thoughts?
2014-11-09 07:49:05

Re: Server problems ?

Board » Technical Support

hmm: Looks much better after clearing the cache, cookies, etc.

BTW. Always happy to help out with anything from design through to diagnosis.

--- Last Edited by dtayls at 2014-11-09 09:18:45 ---
2014-11-06 23:11:07

Re: Server problems ?

Board » Technical Support

Kroppy: FYI, GoToRace links (and a couple of others) in the 'archived races' section are also not relative URLs.
2014-11-06 23:02:07

Re: Server problems ?

Board » Technical Support

Glad I was able to help.

hmm: I can see that downloads of Wx files from the server via IP works fine now but the client still hangs "waiting for Wx download" if I start it using an IP-based URL (eg. http://144.76.111.8/windy/run/765/).

A little packet-sniffing at the client end shows that the client is establishing TCP connections to the server on port 80 but not actually sending any request down the channel. The client then tears down the connection some 6 seconds later. Looks to me like there is also a probably buried somewhere in the client.

Hoping that helps.

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