Permanent catalysts are catalysts that remain for the entire reaction. Some permanent catalysts do not lose any of their cells, even temporarily; these are known as rocks. However, most permanent catalysts lose some (but not all) of their cells temporarily. These permanent catalysts are turned into what is known as an active or recovering state, which evolves back into the original state due to the structure of the catalyst. Typically, if the active region interacts with a permanent catalyst that is still recovering, that catalyst will be destroyed.
Classes of catalyses
There are four main classes of catalyses (and corresponding catalysts): fishhook-type, block-type, boat-type, and snake-type. There are also other catalysts that don't fall into large categories. One example is the eater 3,[note 1] which works in the following situation when the white cell closest to the loaf has formed after the other two white cells and none of the red cells are on.
In order for that white cell closest to the loaf to be born, the cell above and to the right of it must have been on in the previous generation (because none of the red cells could have been on in order for the catalysis to work.
However, it is allowed to die once it has spawned that closest white cell as long as neither of the other white cells die.
This constitute a set of rules that must be followed in order for a successful eater 3 catalysis. Violating these rules will result in the loaf—and sometimes the entire eater 3—being destroyed.
Every catalyst has its own set of rules concerning how it can perform catalyses and not get destroyed.
The standard fishhook catalysis occurs when the two white cells are present in the indicated positions, neither dies by the next generation, the bottom white cell was not born before the top white cell, the red cells are all off, and the red cell just below the bottom white cell is not born by the next generation.
Here are some example catalyses:
In addition, it is okay for the top white cell to die if and only the cell just to the right of it is born right away.
Occasionally, the fishhook may perform a more unusual catalysis where it is converted to another object with tail then back to a fishhook, but these are rare, and they often occur in a quick chain of multiple catalyses beginning with the setup for a more traditional catalysis, so there is no point placing a fishhook where it is not likely to work just because an unusual catalysis is theoretically possible.[note 2]
Even when engaging in an unusual catalysis, the fishhook still has to follow a certain set of rules. None of its cells can die besides one cell at the tip of its pre-block; these cells are marked in white. Also, there are certain cells that must not be born that are marked in red.
There are certain setups that are more likely to result in successful catalyses than other setups. For example, the following type of setup is typically successful.
On the other hand, the following type of setup fails (i.e. the fishhook gets destroyed) much more frequently.
Block catalyses typically occur when a pattern has one cell on its leading edge (row) that is two cells orthogonally away from the closest cell in the block.
In a typical block-type catalysis, that leading edge cell is supported (i.e. has two or three neighbor cells) so that it does not die by the next generation. However, in addition to this, the block sometimes undergoes a reaction where a spark turns it into a pre-beehive, then a later interaction turns the beehive into a grin.
Of course, this will only work if the chaos stays around or leaves then comes back, but because the block is turned into a beehive by a spark, this first step does not affect the active region, so one will know before placing the block whether the active region could turn the beehive back into a block. (This is why it is worth placing blocks in order to use this region, but it is a bad idea to place beehives so that they will be turned into blocks then hope that a spark will turn them back into beehives; one will not know ahead of time whether or not that spark will be delivered.) Although block catalyses can vary, one rule always applies: In order for the block to recover successfully, the back row must not change (although a block can perform separate catalyses from different directions).
Like the fishhook, the block is more likely to work in certain situations than others. For example, if the leading cell does not have an on cell directly behind it, the block catalysis is very likely to be successful.
However, if we advance the pattern by one generation without giving the blocks a head start, the catalyses are not successful.
Also, if the leading two rows of the region about to hit the block only take up two rows instead of three, make sure that they are staggered instead of aligned with the block. If they are aligned, then the block will be destroyed.
This also applies if the interaction starts one generation earlier.
This is how the setup for a boat catalysis looks.
Here are the rules for the boat catalysis.
The important part is that on the first generation, the bottom four rows look like this:
so that on the next generation, the boat looks like this:
(Note that the two cells at the top must die due to overpopulation due to cells in an adjacent row not shown in order for that to work.)
Here is an example:
The snake must function as a rock, meaning that it cannot lose only cells. This is because there are two cells in the middle of the snake that have four neighbors instead of three. If one of the two cells at the top of the snake dies, then one of the cells in the middle will be born in the next generation, which will cause the cell below and to the left of it to be born in the generation after that, which will cause the cell below that cell to be born in the generation after that, which will cause the cell below and to the right of that cell to be born in the generation after that…, and the snake will thus be destroyed. Here are the rules for a snake catalysis.
The white cell must be on and survive to the next generation, the red cells must all be off, and exactly two of the three blue cells must be on so that the cell just to the right of the white cell is born for the next generation. This is because the cell to the right and below that cell will be born for the next generation, it must die right away, and the way to make that happen is with the 4z transition.
This is what the next generation of the snake must look like:
Typically, in a successful snake catalysis, all three white cells will die of overpopulation by the next generation, (The one below the other two certainly will.), leaving the snake clear. The following alternative next generation is also allowed as long as the two above the snake die at the same time, but that type of recovery much less commonly:
Here are four example snake catalyses:
There are hundreds of different catalysts, making trying every single one impractical. Instead, one should try one catalyst from each family in each situation. If it fails, then one should try one or more replacement catalyses based on how exactly the first catalyst failed. There are many guides for replacement catalysts on the forums, such as this guide for catalysts in general and this guide for fishhook-type replacement catalysts, so this article will only cover a small subset of all possible replacement catalysts.
Sometimes, a fishhook will recovery too quickly before all of the sparks have cleared, interact with a spark, and be destroyed.
An eater 2 recovers more slowly and in a different way, so sometimes it gives the sparks enough time to clear so that it doesn't interact with them, but because it recovers in a different way, it can interact with certain sparks and not be destroyed.
In addition, sometimes, an extra cell will end up attached to a fishhook's recovering phase that causes one cell that should die to survive and another cell that should stay dead to be born.
Because an eater 2 recovers differently, this extra cell does not create a problem for it.
Lastly, an eater 2's symmetry allows it to perform fishhook-type catalyses from two different directions, a feature that is used in the Fx158 conduit at the very beginning of this article.
Although there are several instances where a block that fails must be replaced, I'm going to discuss situations where the block can simply be supported. For example, look at this partial pi-to-B conduit:
The block at the top performs a successful catalysts, but the catalysis for the block at the right creates an unwanted line of three cells that turns the block into a loaf. Luckily, this can be suppressed by reinforcing the block with a fishhook, resulting in a successful conduit.
The same trick can also be used to suppress a domino spark that would otherwise destory the block.
If what should be a line of two cells is instead a line of three (i.e. the boat gets turned into a nine instead of its recovery state, try replacing the boat with an eater 5. One example of this is with eating gliders.
Similarly, sometimes, what should be a line of two cells will instead be a line of four or more cells.
In this case, the boat can sometimes be replaced with a cis-boat with tail on fishhook. (The fishhook can be replaced with a snake, aircraft carrier, or other possibilities.)
In order to recover properly, the catalyst requires a spark to turn the hook with tail back into a boat with tail. This spark can come in one of two positions (marked in white).
A spark in a third position will cause the necessary cell to be born, but it will also cause another cell to be born that shouldn't be born, causing the catalyst to be destroyed.
If this spark appears with the replacement catalyst, then it will also appear with the boat, so determining whether or not a boat can be replaced with that catalyst is not guesswork. (The relevant cell is shown in red/white.)
Some other objects can also perform the snake-type catalysis and have better clearance in certain directions. Typically, for most situations where a solution exists, using a fishhook in at least one of two ways will suffice. For example, in this composite conduit, the snake from one of the constituent elementary conduits is too close to a fishhook from the other constituent elementary conduit, causing the snake to interact with the fishhook's recovering state when it shouldn't.
Replacing the snake with a fishhook, which has better clearance in a certain direction, makes the composite conduit work.
Also, if the chaos does not completely clear the snake after the snake-type catalysis, the snake can sometimes be replaced by another catalyst that can recover.
Typically, conduits that rely on sparkers are not as useful because they do not work with every input timing. However, there is one exception: When the sparker is only required for cleanup. For example, consider this partial century-to-glider conduit:
The century leaves a block which, although on the edge of the reaction envelope, cannot be deleted by stable catalysts due to the specific manner in which it is placed. However, it can be deleted by a dot sparker, such as a (period-six) unix.
The only reason why sparkers are discouraged is because they typically cause the conduit to only work at certain timings. Because this conduit can work at any timing, it can be used as a stable conduit.
In addition, if one has exhausted all possibilities of supporting a conduit with stable catalysts, then (and only then) may one try to use sparkers. For example, the following reaction results in the pi with the best clearance of any reaction known:
Unfortunately, it leaves behind a blinker that cannot be deleted with stable catalysts and that causes the conduit to fail on future uses.
When (and only when) one cannot find a stable stabilization, one may use a sparker, as working at some timings is better than working at no timings.
However, this is suboptimal because it does not work at most timings, so this should only be used as a means of last resort; one should not rely on or come in planning to use sparkers.
If one does use sparkers in a manner that prevents the conduit from working at all timings, lower-period sparkers are better because they work at a greater fraction of timings.
- The eater 3 is composed of another catalyst plus a loaf, but because the catalyst without the loaf doesn't have good clearance, it is not important as a catalyst by itself.
- However, as will be described later, placing a fishhook in order to identify a potential replacement catalyst from exactly how the fishhook fails is acceptable, although if one already knows that the fishhook will fail before placing one, one might be able to determine the appropriate replacement catalyst without trying a fishhook.