Revision as of 21:13, 23 August 2010

Born: 10.9.1991

Home: Most, Czech Republic

Contact: ICQ# 273 963 212

My (O)TTD(coop) history:

• Started playing TTD: about 1997 (got it as part of Tycoon Pack)
• Started playing OpenTTD: 2008/09 (first version I played was 0.6.3)
• Discovered #openttdcoop: Feb/Mar 2009, PSG#131 was first coop game I saw (of course I was shocked!)
• Joined #openttdcoop: Apr 2010 (really that late), participated in PSG#180

Specialist on:

• Train logic
• Pathfinder
• CL problems

Weaknesses:

• Rebuilding stuff

Favourite games:

• PSG#121
• PSG#131
• PSG#180
• PZG#13

Ideas, concepts & other junk

On-demand train stopper

Train stoppers are perfect tools to make sure trains have same starting conditions. This becomes very practical for high-speed joins. Trains entering such join at full speed are likely to cause slowdowns on ML (if the line is densly packed, it can lead to huge chain reaction). This can be solved either by enlarging current priority (and that might lead to many missed join opportunities) or by using train stopper.

On-demand train stopper is (currently) only kind of train stopper that is 100% reliable (i.e. stops train in every case). While I didn't really expect this concept to be used in "normal" games, it actually proved very useful in PZG13.

Resources:

• Savegame (r20279)
• Detailed description

Fail-safe NOT/OR gate

As the name suggests, this logic gate can be used as both NOT and OR gate. Its design is similar to NOT and OR gates described in this blog article, but is greatly improved.

The NOT gate "part" might not be that useful, because circular NOT gates tend to have better reaction time (at low speeds), it is however speedproof (works well with high Logic Engine parameters) and cheaper to maintain (TL0.5 variant uses just one engine, while circular NOT gates have to use 4).

Compared to the OR gate mentioned in blog article, it includes two key features: it works without waypoint and it is fail-safe. Normal OR gate has little chance (about 8-10%) to backfire everytime we change its input to red: if the train chooses inner circle (because the signal was green at the moment) and the signal changes to red before the train passes it, we'll likely get stuck train and wrong output (see savegame). It can be compared to previous (i.e. non fail-safe) SMLs - if we trigger priority while the train is shifting, we'll get stuck train and possible jam. It works without waypoint due to some PF magic. Normal OR gate can be changed in that regard too (also in savegame).

This logic gate has been used as a part of waveproof system of PZG13.

Resources:

• Savegame (r20279)

Green burst convertor

This tool is supposed to convert red signal of any length into few ticks of green signal. It is based on Fail-safe NOT/OR gate (mentioned above), but the distribution of prioritized lines is changed to provide green output only if the train is moving (i.e. when we can be sure the train isn't going to say in signal block for longer period). There are two possibilities on when to trigger burst of green signal - either at the beginning or at the end (of red state of input presignal). Convertor which provides green burst at the end (of duration) is much easier to build, however, in some cases we need green burst at the beginning (and it is also more logical). This layout then becomes pretty complicated, because we either have to use some tricks with priority or use a logic gate. See savegame for examples.

This tool can be used for precise train counters and possibly some advanced logic systems.

Resources:

• Savegame (r20594)

LED calculator

Long time ago, I got an idea to combine my previous calculator (simple adder) with LED counter. The main point was to see, if such calculator would be possible to build and because of that, the calculator itself is fairly simple - it can add numbers up to 9 + 9. However, it is fully working and totally fail-safe (i.e. all logic gates are fail-safe). Most of the calculator is LED -> binary and binary -> LED converter, the adder is just small array of half bit adders at the bottom. Just note that the savegame isn't commented.

Resources:

• Savegame (r19523)

Logic Engine 0.6 parameters

Just random note: Circular NOT gates with two trains

• at TL1 stop working with parameter 3816 or higher
• at TL0.5 do not work, due to insane train acceleration

Some examples of how to deal with very high train speeds are included in savegame. The speedproof concept isn't very useful, because normally used parameter (3500) is usually enough to keep reaction time very low and higher values rarely improve this time. High parameter however greatly reduces reaction time of single-train based logic gates (up to some speed, of course). On the other side, the need for unnecessarily more complicated NOT gates likely outweighs the actualy gain.

Resources:

• Savegame (r20279)

Pathfinder behaviour

While pathfinder behaves pretty straightforward when it can find way to its current target, it might behave slightly unexpected with regards of lost (resp. orderless) trains. This savegame shows some problems and unexpected behaviour to be aware of. The savegame itself is little bit older and some problems aren't that strange (resp. are better understood) from today's point of view.

After trying to understand how the pathfinder work in such special cases, I came up to simple conclusion. If the train can find route, use pathfinder debug to find the problem; if it cannot, it's better to "try & fail" (until you find some reasonable solution). Pathfinder is full of surprise!

Resources:

• Forum thread
• Savegame (r20279; fixed PBS overflows to work with >r19896)

To be continued...