Need help with Spectrum emulator and determinism

[IndigoBeetle]

Firstly, sorry if this isn't the right place to ask, but I've been trying for 3 days now to join the "official forum", but it seems that whoever's in control of that wants to make it damn near impossible to register (I have no idea who created the first 16 bit home computer, and besides, first where, US, UK, Europe, Asia?, and then forcing you to wait what seems like an entire day to try again when you get it wrong seems ridiculous).

I'm trying to use MAME, specifically the Sinclari Spectrum emulator part, to form the basis of a regression test suite for my game creator Kwyll. I've managed to make some progress, writing Lua scripts that allow me to capture the state of the keyboard and joystick input ports, and when I press F12 capture a record of the Spectrum screen memory for later ocmparison. Then I've created another Lua script that can read that saved data, replay the input states, and at the right time compare the state of the Spectrum memory with the image saved to confirm the export from Kwyll is consistent.

It seems to work for some content, but for others, specifically one snapshot that cycles the colours and changes the screen contents on keypress input, it fails the image comparison for some capture points. If I save 5 screen captures, and it failes on 3 and 5, it seems it will always fail on 3 and 5, so it's consisten in that regard. However, I can't seem to work out what, if anything, I'm doing wrong to make sure that it consistently produces exactly the same screen memory at the specific frame of execution.

I'm using the "register_frame_done" hook to both capture the data in the record mode, and replay in the test mode. So my question is, is the frame counting and emulator execution deterministic in this regard? If I start the emulation by setting the "snapshot" to my .sna file and reset the "frame" counter at a point in the "register_frame_done" handler to move to the next test, is there any way to guarantee that frame 1, 2, 3, 4, etc. are consistent every time I run the snapshot? I'm a little confused as to why the replay is consistent, in that it fails in the same way every single time, but not consistent between the record and replay, even though I'm checking the "machine:time" value and recording it in the data stream, and during playback confirming they are within 0.00001s of each other.

Thanks for any help, happy to provide the record and replay scripts if that would help understand the problem. Also happy to be told that this is not possible in MAME, that would at least save me wasting any more time chasing.

[cuavas]

emu.register_frame_done sets a callback that will be called when MAME updates the video output. You need to use emu.add_machine_frame_notifier if you want a callback when an emulated “frame” completes (usually at the end of the active area for the first emulated screen in the running system). See the included timecode recorder plugin (plugins/timecode/init.lua) for an example of code that uses both.

[cuavas]

The plug-ins are Lua scripts. They serve as useful sample code demonstrating how to use various functionality as well as adding features to MAME.

[IndigoBeetle]

I looked at the plugin you mentioned when you mentioned it, apart from the plugin paraphernalia, I'm doing pretty much the same thing, and when I used the frame callback, it printed the frame message every frame continuously while running, as soon as I switched to using the machine frame notifier you suggested, it printed the information for 16 frames, and then just stopped. There is nothing in the documentation that I've been able to find that indicates why it would just suddenly stop, which is why I posted here for some clarity on what might be wrong that isn't covered by the documentation as it stands. The suggestion that I "think about it", isn't particularly helpful in resolving that problem.

[cuavas]

Well evidently you’re missing an important thing that every plugin using emu.add_machine_frame_notifier (autofire, cheat, inputmacro, offscreenreload, timecode, and possibly others) does correctly, because all of them work. There’s no magic, I don’t have anything up my sleeve.

[IndigoBeetle]

I clearly am, but it’s not something I’ve been able glean from the limited documentation, or from the plugin code, hence why I can here to ask for help. It’s clear that helping is not something this community values highly, preferring to just tell users to “work it out yourself”. Thanks for engaging, in so far as you have, but I’ve already decided, based largely on this interaction, to pursue an alternative solution.

All the best. MAME is a very cool project, I love it for other things, it’s just not the right tool for this particular project.

[rb6502]

Garbage collection. The thing you're missing is garbage collection.