Game Design, Programming and running a one-man games business…

Coding a load-balanced multithreaded particle system

Posted on July 13, 2025

Background: I am coding a 2D space-based autobattler with ridiculous levels of effects called ‘Ridiculous Space Battles‘. I code my own engine, for fun, in directx9 using C++ and Visual Studio.

Because I love coding, yesterday I found myself wondering how well the multithreading in my game was holding up. So I fired up the trusty Concurrency Visualizer in Visual Studio. I love this tool and have used it a lot on previous games. One of the biggest demands on the CPU for my game is particle processing. There are a LOT of explosions, and other effects, and a crazy number of particle emitters (thousands of emitters, hundreds of thousands of particles). Obviously this would normally be a code bottleneck, so I have a task-based generic multithreading engine that handles it. The main thread builds up a bunch of tasks, the threads grab the next task on the list, and the main thread will wait until the task list is empty. If there are still tasks in the queue, the main thread will do one as well. So how did things look?

Disastrous!

So what is going wrong here? I have a generic ‘marker’ set up to show the span of the main thread’s drawing of the game (GUI_Game::Draw()). Inside that, a bunch of unlabeled stuff happens, but I added spans to show when the multithreaded task called UPDATE_PARTICLE_LIST is called. There are two massive things going wrong here. Firstly, there are only two other threads joining in to process the particles, and secondly one of those updates seems to take 20x as long as the other. Worse still, its the one the main thread chose… so its a huge bottleneck. Technically this is still a speedup, but its marginal. How have I fucked up?

Some background to my rendering algorithm is needed: The game has 2 blend modes for particles. A ‘Burn’ mode, that saturates color and is used for fire, lasers, sparks etc, and a ‘Normal’ mode for smoke and debris etc. The particle effects are batched as much as possible, but I cannot mix those blend modes in a draw call. Also, some particles are below the action (the ships) and some above, to give a semi-3D look and make it look like the explosions engulf the ships. So this means particle emitters fall into one of 4 lists: NormalBelow, BurnBelow, NormalAbove, BurnAbove. This is all fine and works ok. In action, the game looks like this:

Because you can freeze frame and scroll around, everything has to be properly simulated, including particle effects currently offscreen. Anyway it all works, and I have FOUR particle emitter lists. So naturally, to load-balance everything, I gave one list to each thread and considered the job done.

BUT NO.

It turns out that those 4 groups are not equal in size. They are laughably unequal. The ‘BurnAbove’ list contains all of the fire and spark emitters on all of the pieces of all of the hulks from destroyed ships, plus sparks from fiery plasma torpedoes, expended drone explosions, and missed or intercepted missile explosions. Thats MOST of the particles. When I checked, about 95% of particles are ‘BurnAbove’. I had 4 lists multithreaded, but they were not vaguely really load balanced.

Once I realized that the solution was theoretically easy, but fiddly to implement and debug. I decided I would add a new load-balanced list system on top. I created 8 different lists, and when an emitter was created it was added to the ‘next’ list (the next value circled round through all 8), and told what list it was in. When it was deleted, it was removed from the appropriate list. Note that ‘deleted’ is a vague term. I delete no emitters, they get put into a reusable pool of dead emitters, which complicates matters a lot…

So in theory I now have a nice load-balanced series of 8 lists that contains every particle emitter that is currently live. The original 4 lists are still valid and used for rendering and blend mode data, but this ‘parallel’ list system existed alongside it, purely to handle load-balancing. What this means is, that a load-balanced-list may contains particles from all 4 render groups, but this does not matter as I am running update code on them, not rendering!

It didn’t work.

Crashes and bugs and corrupt data ahoy. I worked on it for ages, then watched a movie to try and forget it. Then this morning, after some digging, it was all fixed. What actually was going wrong was related to smoke plumes. Because there are a lot of smoke plumes, and they always reuse the same particle config data, they exist in a separate system, updated separately. I had forgotten this! And what was happening was my new load-balanced lists stupidly included these emitters when they should have been kept out of it. The emitters would expire and be deleted in the multithreaded code, then later accessed by the plume code. CRASH.

I worked it out this morning before breakfast! I was very pleased. You might be thinking, what about the only 2 threads thing? LOL I had hard coded the game to use maximum of 4 threads, probably as a debug test. Idiot. I just changed it to be 10 and everything worked:

This is more like it. I wasted ages trying to get the dumb concurrency visualiser to show my custom thread names instead of ‘Worker Thread’ but apparently thats the category. Not much help. FFS show us the thread names! (They work in the debugger). But anyway, that image above is a snapshot inside a busy battle for the GUI_Game::Draw() showing how UpdateParticles tasks get spread over 8 threads. I’m still not sure why that sixth thread misses out on a task, which gets nabbed by the main thread…

Anyway, the point is it works now, and in theory updating particles is 8x faster than it would be with single threading. I do need to apply the multithreading to a lot more of the game code to get the best possible results. I am testing this on a fairly beefy GPU and CPU (Ryzen 9 5900X 12 Core @3.7GHZ and RTX 3080) in only 1920×1080 res. I want the game to look awesome at 5120 res or on a five year old cheap laptop, so plenty more to do.

If for some reason this tips you over the edge to wishlist the game, here is the link :D.

Solar farm: six months of proper generation plus REGOs.

Posted on July 1, 2025

If you follow this blog a lot, you will know that we actually started generating power on our solar farm in October 2024, but there was some downtime in November, and then more downtime in December due to an extreme storm damaging the site (we lost 10 panels, since replaced), so we didnt have a straight six months of data until yesterday.

Also, because of the way solar is generated over the year in the UK, you want either jan-june or july-dec in order to extrapolate. The output of solar panels is basically a bell curve, peaking mid year, so once you have six months of data, you can make an educated guess (but only a guess) about the whole year. Just who shallow or steep that curve is will depend on a few factors, but in general I think that improvements in panels has flattened that curve a bit. Lots of technical changes to panels mean that they are more tolerant of ‘partial shade’ than they used to be. Handy in a cloudy country!

So how much power have we generated in six months? well its…. 766,739kwh. (766 MWH). So we can assume that if this is a typical year, that would mean 1,533MWH in a year, or 1.5 gigawatt-hours. Enough to run the average TV for 1,700 years. Or enough to fill a large electric car from empty 19,000 times. In some ways this seems a lot, but how does it compare to what we expected?

Well it depends… If I dig up the oldest email about the sites initial plan, the assumed generation output was just 957MWH so this sounds amazing. That was then changed to 1,245MWH it was later changed to 1,347MWH . The final setup for the export meter seems to say that the expected output is 1,339MWH. So the actual expectations are all over the place, but all below the current value. I THINK that we had a very very good April, and that is skewing the results. If we hit 1,400MWH in the year that will be very pleasing. It is too early to really be definitive about whether or not this means that the farm makes a profit. I would be nervous of judging that without a full year. Especially as a maintenance contract is still not signed yet.

In other news…

You may have read posts by me banging on about REGOs. A REGO is a Renewable Energy Guarantee of Origin certificate. When you generate a single MWH of power from a renewable source, you can tell a government regulator (ofgem), and they give you a certificate. There is no subsidy, but you can sell them. Who buys them? Companies and energy retailers who want renewable energy. To be able to sell your power to customers as 100% renewable, you need to buy REGOs to cover all your energy. There is an open and competitive market for REGOs, and currently they are worth £10-£15 per MWH. Thats equivalent to 0.1 to 0.15 pence per unit of electricity, no not a lot from a consumer POV. Like most companies, we have our REGO sales ‘bundled’ in with the PPA (Power purchase agreement) we have with the company who buys our power. In this case OVO Energy.

Thats the theory. In practice, this process is HELLISH. It genuinely feels like ofgem have been told to make the process of getting accredited as impossible as they can. The amount of bureaucracy, inefficiency, radio-silence and pickiness over the grammar and punctuation in every piece of text in every document required in order to qualify is beyond insane. I applied as SOON as was possible (your site has to already be generating, which is stupid as hell), and it still took SIX MONTHS to basically have a form processed and accepted. We even had to argue basic maths with them, such as arguing that 400+500 = 900, and not as they claimed… 810.

Anyway, that insane process (which reminded me of the DNO legal process, which reminded me of the planning process….etc) is finally complete, although not without a formal complain to ofgem about it. And I will not bore you with the details, but suffice it to say that obviously they are still arguing about it, and saying its not right, even though they have approved my site, and approved my output data, and credited me with the certificates which I have lready sold. Its insane beyond words.

And actually the entire process is a colossal waste of time, because there are already a network of organizations who entire existence is simply reading meters and verifying that they are accurate, and reporting that data online. I am charged about £250 a year for this ‘service’ (the real cost is likely under £1, its just a meter). Now ofgem could trivially just connect to the databases for those independent companies, read everyone’s data automatically, and credit the REGOs without any human interaction whatsoever. And as for verifying that the data really is renewable, the people who 100% absolutely independently KNOW what equipment is connected, are the DNO (Energy distribution network operator). There are a handful of meter readers, and a handful of DNOs, and this would be easy…but NO! Lets set up a torturous six month minimum process that involves websites that crash, tons of paperwork, complicated rules and processes and a staggering waste of everybody’s time. Because thats the UK energy industry. Are you surprised your bills are high?

So yeah… its been interesting.

I am HOPING that within a month, I will have stopped getting irritating emails from ofgem, I will not get any more letters about lawyers and leases, from one set of lawyers to another (I would love to jettison the entire profession into the sun at this point), and have a maintenance agreement signed.. and then finally I will be able to basically forget about the farm, apart from enjoying checking the stats!

I do still LOVE the fact that I built it, and own it though. Its awesome :D.

Optimizing load times

Posted on June 29, 2025

I recently watched a 2 hour documentary on the ZX spectrum, which means little to people from the USA, but it was a really early computer here in the UK. I am so old I actually had the computer BEFORE that, which was the ZX81, just a year earlier. The ZX81 was laughable by modern standards, and I expect the keyboard I am using has more processing power. It had an amazing 1kb of RAM (yes kb, not MB), no storage, no color, no sound, and no monitor. You needed to tune your TV into it and use that as a black and white monitor. Its this (terrible) PC I used to learn BASIC programming on.

Anyway, one of the features of ZX81/Spectrum days was loading a game from an audio cassette, instead of the alternative, which is copying the source code (line by line) from a gaming magazine and entering the ENTIRE SOURCE CODE of the game if you wanted to play it. Don’t forget, no storage, so if your parents then wanted to watch TV and made you turn it off, you had to type the source code again tomorrow. I can now type very fast… but the documentary also reminded me of another horror of back then, which was the painfully slow process of loading a game.

These days games load…a bit quicker, but frankly not THAT much quicker, especially given the incredible speed of modern hard drives, and massively so when talking about SSDS. Everything is so fats now, from SSD to VRAM bandwidth, to the CPU. Surely games should be able to load almost instantly…and yet they do not. So today I thought I’d stare at some profiling views of loading a large battle in Ridiculous Space Battles to see if I am doing anything dumb…

This is a screengrab from the AMD UProf profiler. My desktop PC has an AMD chip. I’ve started the game, gone to the ‘select mission’ screen, picked one, loaded the deployment screen, then clicked fight, let the game load, and then quit. These are the functions that seem to be taking up most of the time. Rather depressing to see my text engine at the top there… but its a red herring. This is code used to DISPLAY text, nothing to do with loading the actual game. So a better way to look at it is a flame graph:

I love flame graphs. They are so good at presenting visual information about where all the time is going, and also seeing the call-stack depth at various points. This shows everything I did inside WinMain() which is the whole app, but I can focus in on the bit I care about right now which is actual mission loading…

And now its at least relevant. It looks like there are basically 3 big things that happen during the ‘loading battle’ part of the game, and they are “Loading the ships” “Loading the background” “Preloading assets”. The GUI_LoadingBar code is given a big list of textures I know I’ll need in this battle, and it then loads them all in, periodically stopping to update a loading progress bar. Is there anything I can do here?

Well ultimately, although it takes a bit of a call stack to get there, it does look like almost all of the delay here is inside some direct9 functions that load in data. I am very aware of the fact that directx had some super slow functions back in directx9, in its ‘d3dx’ API, which I mostly replaced, but ultimately I am using some of that code still, specifically D3DXCreateTextureFromFileInMemoryEx…

Now I have already tried my best to make stuff fast, because I’ve made sure to first find the texture file (normally a DDS format, which is optimised for directx to use) on disk, and load the whole file into a single buffer in RAM before I even tell directx to do anything. Not only that, but I do have my own ‘pak’ file format, which crunches all of the data together and loads it in one go, which presumably is faster due to less windows O/S file system and antivirus accessing slowdowns. However I’m currently not using that system… so I’ll swap to it (its a 1.8GB pak file with all the graphics in) and see what difference it makes…

Wowzers. It makes almost no difference. I wont even bore you with the graph.

And at this point I start to question how accurate these timings are, so I stick some actual timers in the code. In a test run, the complete run of GUI_Game::Activate() takes 3,831ms and the background initialise is just 0.0099. This is nonsense! I switched from instruction based to time-based sampling in uprof. That doesn’t now give me a flame graph, but it does also flag up that the D3DX png reading code is taking a while. The only png of significance is the background graphic, which my timers suggest is insignificant, but I think this I because it was loaded in the previous screen. I deliberately free textures between screens, but its likely still in RAM… I’ll add timers to the code that loads that file.

Whoah that was cool. I can now put that into excel and pick the slowest loaders…

Loaded [data/gfx/\backgrounds\composite3.png] in 73.0598
Loaded [data/gfx/\scanlines.bmp] in 20.0463
Loaded [data/gfx/\planets\planet6s.dds] in 11.8662
Loaded [data/gfx/\ships\expanse\expanse_stormblade_frigate_damaged.dds] in 10.7132
Loaded [data/gfx/\ships\ascendency\g6battleship.dds] in 9.3622
Loaded [data/gfx/\ships\ascendency\g5frigate.dds] in 6.9765

OMGZ. So yup, that png file is super slow, and my bmp is super slow too. The obvious attempted fix is to convert that png to dds and see if it then loads faster. Its likely larger on disk, but requires virtually no CPU to process compared to png so here goes… That swaps a 2MB png for a 16MB (!!!!) dds file, but is it faster?

NO

Its 208ms compared with 73ms earlier. But frankly this is not an accurate test as some of this stuff may be cached. Also when I compare pngs of the same size, I’m noticing vast differences between how long they take to load:

Loaded [data/gfx/\backgrounds\composite11.png] in 113.9637
Loaded [data/gfx/\backgrounds\composite3.dds] in 208.7471
Loaded [data/gfx/\backgrounds\composite5.png] in 239.3122

So best to do a second run to check…

Loaded [data/gfx/\backgrounds\composite11.png] in 112.8554
Loaded [data/gfx/\backgrounds\composite3.dds] in 84.9467
Loaded [data/gfx/\backgrounds\composite5.png] in 108.4374

WAY too much variation here to be sure of whats going on. To try and be sure my RAM is not flooded with data I’d otherwise be loading, I’ll load Battlefield 2042 to use up some RAM then try again… Interestingly it only takes up 6GB. Trying again anyway…

Loaded [data/gfx/\backgrounds\composite11.png] in 114.0210
Loaded [data/gfx/\backgrounds\composite3.dds] in 85.6767
Loaded [data/gfx/\backgrounds\composite5.png] in 105.8643

Well that IS actually getting a bit more consistent. I’ll do a hard reboot…

Loaded [data/gfx/\backgrounds\composite11.png] in 104.3017
Loaded [data/gfx/\backgrounds\composite3.dds] in 207.8332
Loaded [data/gfx/\backgrounds\composite5.png] in 141.2645

Ok so NO, a hard reboot is the best test, and swapping to DDS files for the huge background graphics is a FAIL. These are 2048 x 2048 images. At least I know that. The total GUI_Game::Activate is 7,847ms. That png is only about 1-2% of this, and it makes me wonder if converting all the dds files to png would in fact be the best solution to speed up load times? The only other option would be to speed up DDS processing somehow. Having done some reading, it IS possible to use multithreading here, but it looks like my actual file-access part of the code is not vaguely the bottleneck, although I’ll split out my code from the directx code to check (and swap back to a png…)

Creating texture [data/gfx/\backgrounds\composite11.png]
PreLoad Code took 1.0205
D3DXCreateTextureFromFileInMemoryEx took 111.4467
PostLoad Code took 0.0001
Creating texture [data/gfx/\backgrounds\composite3.png]
PreLoad Code took 28.4150
D3DXCreateTextureFromFileInMemoryEx took 71.1481
PostLoad Code took 0.0001
Creating texture [data/gfx/\backgrounds\composite5.png]
PreLoad Code took 0.9654
D3DXCreateTextureFromFileInMemoryEx took 105.2158
PostLoad Code took 0.0001

Yeah…so its all the directx code that is the slowdown here. Grok suggests writing my own D3DXCreateTextureFromFileInMemoryEx function, which sounds possible but annoying.

Ok…mad though it sounds, I’ve done that. Lets try again!

Creating texture [data/gfx/\backgrounds\composite11.png]
PreLoad Code took 0.8327
D3DXCreateTextureFromFileInMemoryEx took 103.4365
PostLoad Code took 0.0001
Creating texture [data/gfx/\backgrounds\composite3.png]
PreLoad Code took 0.6053
D3DXCreateTextureFromFileInMemoryEx took 73.9393
PostLoad Code took 0.0002
Creating texture [data/gfx/\backgrounds\composite5.png]
PreLoad Code took 0.9069
D3DXCreateTextureFromFileInMemoryEx took 105.0180
PostLoad Code took 0.0001

Am I just wasting my life? at least I now have the source code to the DDS loader because it is MY code bwahahaha. So I can tryu and get line level profiling of this stuff now… I’ll try the visual studio CPU profiler:

Thanks Microsoft. But there may be more…

The Visual studio flame graph is saying that actually the raw reading from disk of the file IS a major component of all this, and so is a memcpy I do somewhere… Actually its inside the fast DDS loader, so the flame graph is confusing. The DDS loops doing memcpy calls for each line of data. This is very bad. With a big file, there will be 2,048 calls to memcpy just to read it in. Surely we can improve on that? and yet its clear thats what D3DXCreateTextureFromFileInMemoryEx is doing, as seen earlier. Hmmmm. And now people have come to visit and I have to stop work at this vital cliffhanger…

Visiting the solar farm, 8 months after energization

Posted on June 17, 2025

Because we happened to be (vaguely) in the same part of the country, we decided to go pay a quick visit to the solar farm. Its been energized for about 8 months now, although there have been 2 periods of downtime for some work since then, so we still do not yet have a nice clean 6 months of data to extrapolate from. Also I had my drone with me to take ‘finished farm’ pictures :D.

The situation with the farm is that it is 99% finished. There is some tree planting to do (one of the planning constraints), which will have to wait until later in the year, and also it has a problem regarding shutdown. When the site loses power (due to a grid outage), it then does NOT come right back online automatically, which is frustrating. It should, and its back to negotiations between the construction company and the DNO as to why this doesn’t work yet, and fixing it.

From my point of view, there are also two other things that are still *not done* yet. These are, to get a maintenance contract in place (we are still waiting for quotes from fire suppression system inspectors) and also to get ofgem to finally accept that this is indeed a solar farm. That last point is especially irritating, but I finally think, 8 months after switching on that we are close to the end game on that one. The bureaucracy is insane. Why they need to know how many panels are on each string of each inverter is beyond me. The DNO didn’t even care about this, and we connect this kit to THEIR network… As a reminder, this is so we get accredited to produce REGOs, which are certificates to prove a MWH of power was renewable. You can sell those certificates for about £10 each to companies who want to claim their power is 100% renewable.

Anyway…

Its always pretty cool to see the site, and remember that I actually own it! I love my 10 home solar panels, so going to see the other 3,024 is pretty cool. I was surprised just how NOISY inverters are in summer. I assume this is active cooling, as we were there early afternoon in June. If you think your home inverter for your panels never makes a noise, thats likely because its a 4kw one, and 100kw ones have way more juice flowing through them. I think I could hear the inverters from about 15 feet away.

Broadly things were ok, I was VERY happy to see how clean the panels are, 8 months into energization and probably a year into mounting, so this bodes well for minimal cleaning costs. How grubby panels get really depends on circumstances. This is a livestock field, so crop dust is not constantly blowing near them, which probably helps. I did encounter a bunch of things that I had to complain to the construction company about. I guess its just like having builders come work on your house, but 100x bigger in scale. I really hate that side of the project, but it comes with the territory. It was also good to meet up with the landowner, who is a great guy, very understanding, and a great ‘man on the ground’ who can tell me about any problems directly without it being filtered through a third party.

One of the main reasons I wanted to take a look again was to try and get better drone pictures, as last time the site was not 100% finished and my drone had software issues (DJI apps suck!). This time it worked, and I took some, as you see, but it was pretty windy. Being on a hilltop does not help, and I braved the ‘LAND DRONE IMMEDIATELY’ warnings as long as I could, but they are obviously not pro level snaps :D. I also found one broken panel, from when the site suffered storm damage, which shouldn’t be left there really. It was interesting to see a folded and broken solar panel though. You don’t see many of those.

Overall I’m happy, the site is generating nicely in summer. the end of this month will be when I can do a proper financial analysis, as the output mirrors around midsummer so 6 months data gives me a great yearly prediction. I really want it to break even!