(some) hopper clocks misbehave, when covered by furnaces

[bnvy]

A year or two back, one technique for reducing redstone lag was to cover hoppers with furnaces or other blocks with inventories. With Forge 2002, the "amputated" version of Sethbling's hopper clock produces flickering outputs when furnaces are placed above the hoppers, because items sneak through to the next hopper instead of being held up.

 

The "basic" and "simplified" Sethblings, and Ethonians (where you can cover the hoppers) don't seem to be affected. Removing the furnaces makes the amputated clock function properly, but in vanilla 1.10.2 the furnaces don't cause problems. Something has changed the timing or sequence of hopper transfers.

 

The problem exists at least in 2002 and 2006, but not in 1937/1.9.4, using only Forge, no other mods, standard launcher. Easily recreated in a new world (redstone-ready preset) with no other stuff going on. Build the amputated clock, give it about eight items or so, watch it cycle properly a few times, then place empty furnaces above the hoppers and it will start flickering within seconds.

[RANKSHANK]

https://athenadennisfreelancewriter.files.wordpress.com/2014/02/bug_vs_feature.gif[/img]

 

This feels relevant.

[LexManos]

No idea what you're talking about, you should either make a video or a world explaining that you mean better.

 

[bnvy]

Sorry that wasn't clear enough. Download the world named 'hopper-furnace' (first use of google drive, but I think it works):

 

https://drive.google.com/folderview?id=0B2xMRzJv9clVc09oYlAwNW9wN1E&usp=sharing

 

It contains three hopper clocks, and nothing else. All are within the same chunk, everything at least two blocks from the border, with a rotated copy of the smaller clock to demonstrate it's not an orientation issue. The clocks are labeled with names used on the wiki page for clock circuits http://minecraft.gamepedia.com/Clock_circuit#Multi-item_hopper_clock

 

Load the world with Forge 2002. Initially the clocks all work normally, such that the two lamps on each will be alternately lit every few seconds.

 

Next, place furnaces above all the hoppers. The behavior of the larger clock remains unchanged. However, the lamps on the smaller clocks will now start blinking, because the items are circulating through the hoppers instead of being held until all are collected in one.

 

Leave the furnaces in place.

 

Save, quit, load with vanilla 1.10.2. The small clocks return to normal, expected behavior after a few seconds.

 

Save, quit, load with 2002. The small clocks will begin blinking again. Remove the furnaces and they return to normal behavior.

 

The blinking sequence is not always the same – it depends on how the items spread out through the hopper ring, probably dependent on the order in which you place the furnaces, and/or where the items happen to be at the time, and of course the fact that lamps are slow to respond. However, if you place/remove the furnaces two or three times, you will likely find a case where one of the comparators never lights up at all, even though you can see items passing through the hopper. This will likely get you closest to the problem.

 

You may also wish to confirm that using 1937, the furnaces make no difference, so the problem was introduced sometime since then. It seems quite likely other blocks with inventories may have the same issue as the furnaces, but since this is perfectly repeatable for me I haven't explored that.

 

It's not that I was looking for lag reduction techniques, I simply had an older world where several things stopped working, and this turned out to be the cause. Thought you should know.

[LexManos]

Ya its much better when you submit full details and a test case we can actually debug it then.

Either way the bug has been fixed. https://github.com/MinecraftForge/MinecraftForge/commit/3e6099055e228dc73a0947047c725a0548809f07

Go get the latest 1.10.2.