Open source?

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bonoetmalo
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Open source?

Postby bonoetmalo » Wed Mar 15, 2017 12:31 am

I tried searching for an existing post but "source" is an ignored keyword in the search filter. Lovely.

Is there any plan to release the source code for the emulator?

P.S. I bought the app a month ago, so settle.
Exophase
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Re: Open source?

Postby Exophase » Wed Mar 15, 2017 4:14 pm

No plans for the time being. If I ever release the source it'd probably be after we no longer sell it on Android, since I don't think it really makes much sense to sell open source software. It could happen eventually but probably not eg this year.

Is there something in particular you had in mind with the source? Like a new port, a fork, or do you just want to see how it works?
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huckleberrypie
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Re: Open source?

Postby huckleberrypie » Wed Mar 15, 2017 5:12 pm

Exophase wrote:No plans for the time being. If I ever release the source it'd probably be after we no longer sell it on Android, since I don't think it really makes much sense to sell open source software. It could happen eventually but probably not eg this year.

Is there something in particular you had in mind with the source? Like a new port, a fork, or do you just want to see how it works?

I've seen commercial open source software before, but given how emulator projects are being subject to knockoffs on Google Play lately...
bonoetmalo
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Re: Open source?

Postby bonoetmalo » Wed Mar 15, 2017 5:34 pm

Exophase wrote:No plans for the time being. If I ever release the source it'd probably be after we no longer sell it on Android, since I don't think it really makes much sense to sell open source software. It could happen eventually but probably not eg this year.

Is there something in particular you had in mind with the source? Like a new port, a fork, or do you just want to see how it works?


Yeah. Was just a curiosity, so no worries. Listened to the TechStuff episode on emulators, and was surprised there was finally a DS emulator that can run this well. Last time I checked back when Black/White came out they were still awful, even on desktops.
TkSilver
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Re: Open source?

Postby TkSilver » Wed Mar 15, 2017 9:03 pm

bonoetmalo wrote:Yeah. Was just a curiosity, so no worries. Listened to the TechStuff episode on emulators, and was surprised there was finally a DS emulator that can run this well. Last time I checked back when Black/White came out they were still awful, even on desktops.


Then be prepared to be amazed at no$ and DeSuME if you ever decide to look at desktop versions. I am pretty sure Exo uses a lot of hacks and other tricks to get DraStic up to the speed it runs at. Where I think the desktop DS emulators are more accurate.

Kinda like snes9x vs zsnes was. 9x used to take a lot more to run then zsnes (back in the late 90's early 2000's), but 9x had less little issues due to higher accuracy.
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huckleberrypie
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Re: Open source?

Postby huckleberrypie » Wed Mar 15, 2017 10:28 pm

TkSilver wrote:
bonoetmalo wrote:Yeah. Was just a curiosity, so no worries. Listened to the TechStuff episode on emulators, and was surprised there was finally a DS emulator that can run this well. Last time I checked back when Black/White came out they were still awful, even on desktops.


Then be prepared to be amazed at no$ and DeSuME if you ever decide to look at desktop versions. I am pretty sure Exo uses a lot of hacks and other tricks to get DraStic up to the speed it runs at. Where I think the desktop DS emulators are more accurate.

Kinda like snes9x vs zsnes was. 9x used to take a lot more to run then zsnes (back in the late 90's early 2000's), but 9x had less little issues due to higher accuracy.

Yeah, that's the tradeoff with Drastic. But then again it's to be expected the more recent the target platform is.
Exophase
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Re: Open source?

Postby Exophase » Thu Mar 16, 2017 3:11 pm

TkSilver wrote:I am pretty sure Exo uses a lot of hacks and other tricks to get DraStic up to the speed it runs at. Where I think the desktop DS emulators are more accurate.


There are some things about DeSmuME that are more accurate and expensive, like some details with DMA timing and if you enable advanced bus timing it emulates cache misses which gets more accuracy at a big cost. DraStic tries to do some other things to improve timing accuracy that DeSmuME doesn't, like gamecard read latency (not that expensive) and load instruction interlocking (not expensive for a recompiler). While the advanced bus timing can make a significant difference in accuracy for DeSmuME I doubt it's something that's ever enabled in any of its mobile ports, and I'm not sure how it interacts with its recompiler.

For 2D, 3D, and geometry the accuracy is pretty similar for the most part. DraStic is faster because it's more optimized and vectorizable, and contains a lot of NEON code. There's a few features that are missing on DraStic like OBJ mosaic, but in other ways it's more accurate - the geometry engine operates with the right integer precision and the 3D rendering at least tries to be close, while DeSmuME does all of this with floating point which is pretty significantly off. Neither emulator supports anti-aliasing. Because of this DraStic doesn't have half-blended edge marking, while DeSmuME does but only because it performs edge marking in a way that's totally different from how a real DS does it.

I'm not sure about what No$ supports these days and how accurate it is.

I think if DraStic was changed to be as accurate than DeSmuME in all ways (while still retaining the ways in which it's more accurate) it'd be decently slower than it is now, but still much faster than DeSmuME. Unfortunately I kind of made it hard to really move in this direction because when you try to make something more accurate it might fix some games while breaking others, and I don't really have a lot of room to mess with this (I can say with confidence that DeSmuME's emulation is far from totally accurate here, but they might have struck some heuristics that just work better with more games after enough experimentation). For that reason there are some things like DMA delays that are implemented but only actually enabled for like one game.

If anyone's interested these are all of the per-game hacks currently in DraStic:

Mario & Luigi: Bowser's Inside Story: +2 clocks per instruction, *2 DMA cycles, *4 geometry cycles.. this game has a really nasty race condition
Sonic Chronicles: +1 clocks per instruction, apparently this isn't enough to make it actually work.. oops.
Art Academy: Hack to make vcount read as 192 momentarily before the interrupt triggers, to get past an idle loop. On a real DS this works because of a nuance in interrupt latency. DeSmuME emulates this some other way without a per game hack.. it might be possible to emulate correctly without a big expense but I didn't want to take the risk for this one edge case.
Yu-Gi-Oh 5D series: +1 clocks per instruction, DMA consuming CPU time
Spider-Man Shattered Dimensions: +1 clocks per instruction
Puppy Palace: +2 clocks per instruction
Ore ga Omae o Mamoru: +1 clocks per instruction
Legend of Kay: +1 clocks per instruction
American Girl games: geometry swaps stall the geometry engine (this was originally not a per-game hack but broke some other stuff, same thing happened with DeSmuME.. it's because the stall conditions aren't totally modeled right, it's complex)
Zhu Zhu Babies: +1 clocks per instruction, only for the E version
Will o' Wisp DS: +1 clocks per instruction
Element Hunters: +1 clocks per instruction
Florist Shop: Force undeferred 2D, normally the 2D rendering happens in between updates to IO regs/palette/OAM but not VRAM writes (because the VRAM mapping is complex and hard to defer) and this causes problems if the game writes to active VRAM in the middle of the frame, which this does because it uses a dumb framebuffer that's not properly vsync'd.. I'm sure I could handle this without resorting to hacks with a more sophisticated dynamic detection method, it just didn't feel worth it at the time.

It can be seen that MOST of the hacks are adding an extra clock cycle per instruction (for ARM9). This is done in lieu of stalls that you would see from cache misses, wait states to uncached accesses, write buffer fills, dynamic multiplication costs, and probably some other stuff. My general philosophy in timing emulation is to try to make it no slower than a real DS. Usually this results in the games working, although sometimes they perform better than they did on the real thing. Sometimes you have weird race condition bugs in games that breaks them, so this makes it a little slower to try to compensate. Usually the game just breaks in one place and this gets it past that problem area.

In hindsight it probably would have been better to add a statistical cost to memory instructions since that would more closely model the real performance. I'd also like to experiment with other more accurate emulation options and their performance impact, it's just not something I've been able to get to.

DeSmuME does some of this all the time, and more of it with advanced bus timing. But it's not always that accurate. Here's an example: in Kirby Superstar Deluxe, the emulation being too fast on DraStic causes the videos to run too fast. On DeSmuME with advanced bus timing disabled, they run at the right speed, probably because of VRAM write waitstates being added. But if you turn on advanced bus timing, they now run too slow! And this could be because it doesn't emulate the ARM9 write buffer; when there's a cache miss on a store you pay the full price for it while on a real DS you'd only pay for it after the write buffer is full or if there's a subsequent load stall. So while you could say this is more accurate because it at least does something, it's definitely still a simplified model that makes some concessions.
Fefo
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Re: Open source?

Postby Fefo » Thu Mar 16, 2017 5:07 pm

Wow, this is far less hacks than I imagined. Great read.
BE ATTITUDE FOR ENGRISH
paperplane
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Re: Open source?

Postby paperplane » Sun Mar 26, 2017 10:43 am

I don't use any Google services on my devices, (I have a Samsung Tab pro and a Nexus 5x) I also exclusively use open source applications from sources like the F-Droid repository, with the exception of apps like Caustic and such, (which is still working if you buy the key app and use an IPtables firewall in conjunction) so an open souce verison would be great for people that do not have the Google framework installed on their devices.
But on the other hand it is very understandable that you would like to earn the money for the emulator and the hard work that comes with it.
Isn't there a way to pay and install the emulator without the use of the playstore, and at the same time keep the emulator out of the hands of software crackers. (Which I would NEVER download considering it most likely will be loaded with virusses and spyware.)
I now use a NDS RetroArch core for Android, but it is nowhere as fast and has the options/possibilities that Drastic has.
It would be nice if there was a universal payment method that both protect the sofware builders' code, and at the same time have a licence verification without the need of an appstore/market.
-Sorry about my poor English.
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slamandar
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Re: Open source?

Postby slamandar » Fri Mar 31, 2017 9:24 am

Don't do it, don't make it open source .

remember in 2014 when people struggling with NDS4Droid, they didn't even think about new features or different screen size options, multiplayers..., all what they wanted was an emulator that can run Ds games with a decent speed.

you did a good and hard work with this emulator and you have the right to earn from it and the keep it close source :)
Sorry if my English is bad, I'm French !

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