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Author Topic: Dwarf Fortress and CPU Processors  (Read 16896 times)

Putnam

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Re: Dwarf Fortress and CPU Processors
« Reply #30 on: May 25, 2016, 05:18:54 pm »

Wow, okay, I'm pretty sure the official word was never "never". I'm not sure why people make shit up so much about this topic in particular.

Shonai_Dweller

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Re: Dwarf Fortress and CPU Processors
« Reply #31 on: May 25, 2016, 05:29:31 pm »

It will have to be done before v.1.00.0, as will multithreading, if Toady wants DF to be more than a lagfest of suck. The things on his to-do list - oh! such wonder! I can hardly wait for them to come. But they will require rewrites to handle multithreading and 64-bit. So why not now? A stitch in time saves nine.

Speaking of that particular Thralled Elephant in the room, has there been any more word on the possibility of multi-threading? A while ago the official word was 'never', then a little later it was 'eventually, but I don't really want to'. What are we at now?
According to the podcast a month or so back it was (paraphrasing) 'There are various issues which we have optimization plans for and none of them require multithreading'. You'd have to listen for yourself to catch exactly what he said.

Edit --March 13th devlog.
« Last Edit: May 25, 2016, 05:31:07 pm by Shonai_Dweller »
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Jimmius

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Re: Dwarf Fortress and CPU Processors
« Reply #32 on: May 25, 2016, 06:25:16 pm »

Wow, okay, I'm pretty sure the official word was never "never". I'm not sure why people make shit up so much about this topic in particular.

oh cmon, allow me *some* use of hyperbole, we're on the internet ffs
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RoaryStar

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Re: Dwarf Fortress and CPU Processors
« Reply #33 on: May 25, 2016, 09:05:18 pm »

Wow, okay, I'm pretty sure the official word was never "never". I'm not sure why people make shit up so much about this topic in particular.

oh cmon, allow me *some* use of hyperbole, we're on the internet ffs

That's like exaggerating by a factor of infinity. I'm sure that's much worse than hyperbole.

On topic, though, is that in all seriousness multithreading requires massive rewrites and it still won't help if your L4 cache is too small since many processors share the L4 across multiple cores. If you multithread to four threads you might have 3x processing power (overhead considered) but it's still limited by cache misses, which take over 100x the cycles to retrieve data than usual, so if misses are way too common then in total you have about 0.9x speed than usual.
Multithreading doesn't matter much if you can't get the data to execute it on.
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Shonai_Dweller

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Re: Dwarf Fortress and CPU Processors
« Reply #34 on: May 26, 2016, 01:13:17 am »

Woohoo the first benefits of going 64-bit are confirmed.
New compiler=new tools=less spelling mistakes.
It's a good start anyhow. Destroyed system less so...
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Mesa

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Re: Dwarf Fortress and CPU Processors
« Reply #35 on: May 26, 2016, 08:43:45 pm »

The admittedly niche benefit of the game becoming 64-bit is that us Linux users won't need to keep the 32-bit versions of whatever libraries DF needs to run anymore. (not just for DF, anyway...)

(It's a very first world problem to have, I know.)
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galneon

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Re: Dwarf Fortress and CPU Processors
« Reply #36 on: May 28, 2016, 01:43:55 pm »

Anyone who missed them a few months ago should read khearn's words about DF's bleak future and its need for dramatic reform beginning with this post.
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TheBiggerFish

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Re: Dwarf Fortress and CPU Processors
« Reply #37 on: May 28, 2016, 11:16:52 pm »

And then the posts after them.
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Shonai_Dweller

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Re: Dwarf Fortress and CPU Processors
« Reply #38 on: May 29, 2016, 01:08:09 am »

And then the posts after them.
And then Toady's comment on this thread in the podcast.
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galneon

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Re: Dwarf Fortress and CPU Processors
« Reply #39 on: May 29, 2016, 08:19:08 pm »

Thanks, I hadn't listened to that. After hearing Toady's response and the naivete exhibited therein, I'm more pessimistic than ever.
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Putnam

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Re: Dwarf Fortress and CPU Processors
« Reply #40 on: May 29, 2016, 09:02:58 pm »

And then the posts after them.

This thread resulted in some excellent insights from khearn who could speak in more specific terms regarding the inevitable day of reckoning, and I hope Toady reads it at some point.  Khearn's well-established ethos warded off most of the rowdy locals in denial as DEET repels bloodthirsty mosquitoes.  I was not so protected, but I'm honored I was able to provide a platform for this dose of reality despite the protectionist furor it initially attracted.  I've emerged unscathed.

ignore the troll pls

Bumber

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Re: Dwarf Fortress and CPU Processors
« Reply #41 on: May 29, 2016, 11:01:56 pm »

And then the posts after them.
And then Toady's comment on this thread in the podcast.
What was his comment?
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Shonai_Dweller

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Re: Dwarf Fortress and CPU Processors
« Reply #42 on: May 29, 2016, 11:49:59 pm »

And then the posts after them.
And then Toady's comment on this thread in the podcast.
What was his comment?
My recollection of it is 10 posts above yours.
It's towards the end during the q&a if you want to check it out for yourself. I asked what he thought specifically about the two threads on the front page at the time insisting that DF is doomed due to lack of multithreading.

I'm not technically minded enough to know the truth of it, but I do wish people wouldn't keep assuming that Toady's decades of programming experience mean nothing because he's 'not a programmer'.

Haven't you ever got better at something??
« Last Edit: May 29, 2016, 11:51:34 pm by Shonai_Dweller »
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SpoCk0nd0pe

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Re: Dwarf Fortress and CPU Processors
« Reply #43 on: May 30, 2016, 03:27:42 pm »

For Dwarf Fortress, multicores don't matter because it's single-threaded. This means most mid- or top-line CPUs from the past 5 or so years are all going to be fairly similar, although I think i7s are the fastest single-threaded from memory.

What really slows DF down, however, is cache missing. 

You want a very large cache if you can get it.  Sadly, you'd need somewhere around to 1gb in cache to really run the game entirely on cache.  A quick Googling says that the best is somewhere around 128 mb in a L4 cache, which isn't really there yet, but might get there in a few years.

Failing that, you want the fastest memory possible.  What you really want is the lowest possible CAS latency. (See here for a little guide on it.)

The reason for this is that most of DF is not really complex math that will tie up a CPU, it's actually a bunch of "checks".  The big drains on FPS are things like pathfinding (which involves querying the map almost at random - which foils caching unless you have some crazy huge cache large enough for the whole map, and also foils prediction in slicing), checks on item status as you get more and more random garbage in your fort (again, involving checking such a large table of data it can't be cached), or fluids, which are problematic mainly because they force redraws of the connectivity map... which again means a huge table of data too big for the cache.  Ultimately, this means that your RAM is going to need to respond quickly to queries of small bits of data that the CPU cannot predict like it normally can, so having the lowest CAS latency possible is the best way to improve speed.  (It's also not strictly the most expensive thing you need to buy, since you don't need to buy tremendous amounts of RAM for DF... at least, not yet.)
So the answer is either i7-4790K for it's low memory access latency and high clock speeds or the i7-5775C for it's eDRAM? (paired with the lowest latency ddr3, probably g.skill from my experience?)
« Last Edit: May 30, 2016, 03:29:20 pm by SpoCk0nd0pe »
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galneon

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Re: Dwarf Fortress and CPU Processors
« Reply #44 on: June 01, 2016, 10:37:18 am »

And then the posts after them.

This thread resulted in some excellent insights from khearn who could speak in more specific terms regarding the inevitable day of reckoning, and I hope Toady reads it at some point.  Khearn's well-established ethos warded off most of the rowdy locals in denial as DEET repels bloodthirsty mosquitoes.  I was not so protected, but I'm honored I was able to provide a platform for this dose of reality despite the protectionist furor it initially attracted.  I've emerged unscathed.

ignore the troll pls

You're still thinking about that reply? My apologies if you're an actual mosquito--I couldn't have known. :/
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