Quick Recap
There's been a lot of detail in the last couple of posts, and there's probably some danger of getting lost in the weeds here. Time for a short summary of what pieces of the RCT project have been completed so far, and which pieces are still left to do.
1. COMPLETE: Fifteen gliders crash to create four glider-producing switch engines, which send long streams of gliders to collide at the RCT epicentre.
2. COMPLETE: A sixteenth glider hits the initial output gliders from that glider-stream collision, to provide a target elbow for the RCT's initial construction arm.
3. COMPLETE: Using a "divide by two and take the remainder" mechanism, the RCT repeatedly measures the parity of the distance between the epicentre and the southeastern GPSE, and emits either a single glider or a pair of gliders toward the target elbow.
4. COMPLETE: Recipes are known that create a target a safe distance off to the side, move the elbow forward and back as needed, and emit gliders on any chosen lane. The RCT's initial construction arm is therefore provably universal.
5. COMPLETE: The RCT's initial construction arm builds a DBCA (see previous post) and routes data from the RCT into these, for a ~12x improvement in construction efficiency.
6. PARTLY COMPLETE: The DBCA builds an ECCA -- Extreme Compression Construction Arm, see below -- and routes input RCT data into it, for an additional ~30% efficiency improvement. The ECCA has been completely designed (implementation details here) but as of 5 July 2022, integrated self-destruct circuitry still needs to be added.
7. PARTLY COMPLETE: The DBCA builds a "catcher" for incoming GPSEs, then builds a pseudo-BSRD (more details here) and routes all remaining RCT construction data into it. The pseudo-BSRD delays the final construction and cleanup stages until after the GPSEs have crashed at the epicentre and all debris can be safely cleaned up.
8. TBD: The ECCA, working with data emitted by the pseudo-BSRD, cleans up all of the DBCA's circuitry, and all of the non-periodic ash from the GPSE crashes.
9. COMPLETE: The ECCA builds a seed for the ATBC -- the Actual Thing Being Constructed, which is the real end goal of one of these RCT construction/deconstruction projects. A sample ATBC seed for a large object not ordinarily constructible with 16 gliders can be found here. When triggered, the seed will build Alan Hensel's decimal counter. To construct the seed, the ECCA will fire 7284 slow gliders, which will be encoded by about 52,000 bits coming from the RCT mechanism.
10. MOSTLY COMPLETE: The ECCA builds and triggers 106 Cordership seeds. These Corderships fly past the periodic GPSE ash and clean it all up. The required fleet of Corderships has been designed and tested; a recipe to build and launch them one at a time has not been compiled yet, but this is a fairly straightforward task.
11. PARTLY COMPLETE: The Corderships are caught and cleanly removed by "Corderabsorbers" which will have been constructed at the sites of the "ash blobs" left behind by the GPSE launches. All Corderabsorbers have been designed and tested, but recipes to build them have not been compiled yet. For the southwest Corderabsorbers, this will require using slow^2 salvos. No generalized compiler for slow^2 salvos exists at the moment, but one can easily be written.
12. COMPLETE: The final Corderabsorber in the southeast releases an output glider, which triggers the ATBC seed. All cleanup is complete, so the only thing left in the Life universe is the ATBC.
The ECCA
A detailed description of the Extreme Compression Construction Arm can be found here.
EDIT 11/11/2022: I'll leave this post as a snapshot of the RCT blueprint as it was at this stage of development. The final design (see links in the November 10 post) still works very much along these same lines, but several changes have been made to the build order and other details. For example, to improve Golly's ability to explore the final stages of the pattern, the Actual Thing Being Constructed has been moved to the epicentre instead of the far southwest corner.
