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1  Game Development / Game Mechanics / Re: Hardware-like software cursor. on: 2016-05-02 14:30:57
I (honestly) was thinking about that solution too - but it makes your (gameplay) framerate issues even worse, especially when vsync is on.
If it's dynamic enough and only activates at <half the monitor's refresh rate, it should be OK. It might improve the perceived responsibility.
Could you also just repaint the small cursor and the small 'dirty' section where it used to be painted? Might save some time.
2  Discussions / Miscellaneous Topics / St Petersburg paradox on: 2016-05-02 13:05:23
This is not related to java, it's a maths problem.
I was wondering if any of the many smart maths people here could take a look at this problem about the St Petersburg paradox? I posted it on MathExchange but the dweebs there put my question 'on hold' for some reason.

I've tried to verify the below quoted statements on wikipedia because I think they're mixed up:

"For example, with log utility a millionaire should be willing to pay up to $10.94, a person with 1000 should pay up to 5.94, a person with 2 should pay up to 2, and a person with 0.60 should borrow 0.87 and pay up to 1.47."

According to my simulation of results in a spreadsheet, I calculate that a natural logarithm utility function player with an initial wealth of 1000 (not a million) would pay a maximum of 10.95, rounded to the nearest cent, to participate once in the game. Here is a link to my spreadsheet simulation calculations that demonstrate my above findings that a player with 1000 initial wealth will only pay 10.95, not 5.94 as is stated in the wikipedia article.
Apologies if I've made a silly error. Just wanted to check.

3  Discussions / Miscellaneous Topics / Re: What I did today on: 2016-04-20 04:51:35
Azul Systems have ported OpenJDK to run natively on ARM - I'll be evaluating it soon. I imagine it to be more or less the same as the Oracle offering, performance wise (that is, very good indeed).

Cas Smiley
That's exciting. I found the announcement about it here:
Too bad that I bought a 64 bit ARM board rather than a 32 bit one. This Azul JVM is only for 32 bit.
Will be interesting to hear your experiences with it on the raspberry pi 3.
4  Games Center / Showcase / Re: Amoebam - LD35 Compo Entry on: 2016-04-19 13:05:48
Worked well for me, chrome windows 7 html5.
Impressive for one weekend.
But I must say it's pretty hard! I could barely finish the last jump in the tutorial. And then trying to kill the enemies without being able to shoot while jumping was tough. But I expect that these little things are very hard to iron out in such a short time.
Nice work overall. Finishing a jam with something to show is a victory in itself  Cool
5  Discussions / Miscellaneous Topics / Re: What I did today on: 2016-04-19 12:59:46
One thing that seems strange is this quote from the UDOOx86 kickstarter:
"Quad Core 64-bit new-generation x86 processors"

I thought x86 meant 32 bit?
Given that the processor is actually 64 bit, shouldn't the whole project be called the UDOOx64 rather than UDOOx86  Huh

6  Discussions / Miscellaneous Topics / Re: What I did today on: 2016-04-19 12:51:30
Link share Wink
- X86
- Intel® Quad Core up to 2.24 GHz
- 4 GB of RAM
Estimated delivery: Nov 2016
X86 - Win ^^
Interesting board, thanks for sharing.
I see that the power consumption is said to be between 5 and 6 Watts which is only double or triple the ARM boards.
Here are the board's processor specs for the Intel® Celeron® Processor N3160 (2M Cache, up to 2.24 GHz).

Interesting to see that it's a Celeron which as a desktop has a bad reputation for being slow but comparable to the ARM boards it must be relatively faster. I notice that this incarnation of the celeron was released in 2016Q1.
I hope this UDOOx86 board takes off and gives rise to lots more competition. One of the pains with the ARM boards is that few programs work with them. Even java is a pain to run on ARM since Oracle attempt to charge a licensing fee for the embedded Oracle JDK if you distribute a commercial program, unlike the regular JVM.
Also, I haven't been able to find an ARM64 headful (graphics capable) Oracle JVM, embedded or not. This is not a big problem since the openJDK arm64 JVM works headful but I suspect that it's slower than the oracle one.
Having a fast and power-efficient x86 board would be great from a software point of view since ordinary java will work on it. Also, the linux operating systems on x86 are fully functional and stable, unlike arm64 which is a big headache. For example, Chromium browser doesn't work on Ubuntu arm64 at the moment, among other driver and OS problems:
7  Game Development / Networking & Multiplayer / Re: Kryonet hosting? Where and how? on: 2016-04-12 06:51:24
I use ramnode and have been impressed with how cheap it is at $5 per month with 2 cores.
Also, in the last few years I've never had to restart the server. I guess that's Linux and Java stability.

Sounds like you're using libgdx, but if you end up running tomcat for a website, Java melody is very handy

8  Games Center / Showcase / Re: Age of Conquest IV for PC, Mac, Linux, Android & iOS (Strategy/WEGO) on: 2016-04-07 14:16:57
Yes the scrolling works well, I was just commenting about how the window itself wasn't maximised, it took up only about 3/4 of the screen. Seems like a fully expanded default window would be better for immersion and so on. I am using windows 7.
9  Games Center / Showcase / Re: Age of Conquest IV for PC, Mac, Linux, Android & iOS (Strategy/WEGO) on: 2016-04-06 13:19:58
I downloaded it and it worked well. I must say I was very surprised and happy to see that the game is largely free, I was only expecting a demo.

The graphics, smoothness and responsiveness were great. The resizable-window was cool, rather than full screen exclusive. But perhaps the window should be maximised by default rather than small because then it would be easier to scroll by moving the mouse to the screen edge like a normal RTS. The ctrl - mouse wheel zoom is a great idea.

I did the tutorial and to be honest I didn't get a good feeling for how the game is supposed to work. I was a little confused about which territory was mine since I could see all territories. The intro mentioned Rome, but my people seemed to be in North Italy or France. I couldn't seem to control the Rome city. Perhaps a pulsating colour on your own territories would make it more obvious which cities are yours.
It's not clear how to move troops, I expected to slide them from where they were to where I wanted them to go, like Civ2. I did attack a town but then I couldn't find my troops anymore and couldn't seem to attack anything else. I had to google what the acronym WEGO is, it might be worth writing what it means.

Perhaps a 2 minute youtube video detailing how to do things before the tutorial would be nice.

Overall, it looks like a great game and I intend to give it more time this weekend.

EDIT: forgot to say, WEGO is a great idea, especially for multiplayer where it is super frustrating waiting for other players. Here's a definition for those  like me who don't know what WEGO is:
Turn-based games come in two main forms depending on whether, within a turn, players play simultaneously or take their turns in sequence. The former games fall under the category of simultaneously-executed games (also called phase-based or "We-Go"), with Diplomacy being a notable example of this style of game.
The WEGO system is this:   Everyone issues their orders for the turn at the same time.  You hit "End Turn" and all side's actions are made at the same time.  It eliminates the unbalanced turn-based part but also adds an extra dimension by attempting to anticipate what your enemy might do while your orders are being carried out.
10  Games Center / Showcase / Re: Age of Conquest IV for PC, Mac, Linux, Android & iOS (Strategy/WEGO) on: 2016-04-06 09:34:18
This looks very impressive, similar to Risk and Diplomacy (board games) or Civilisation (PC).
Well done implementing the multiplayer aspect. I'm looking forward to trying it.
11  Discussions / Miscellaneous Topics / Re: What I did today on: 2016-04-04 14:37:04
To add to Grunnts' point, students and teachers at uni are very interesting and you'll probably enjoy meeting new friends and colleagues more than anything else. It's one of the few real (non-internet) forums where you can have an in-depth technical debate about topics that you're interested in. I'm still studying and it's a high point in my week when I have a class with a knowledgeable teacher who can provide some new ways of looking at a problem that I wasn't aware of.

University is not actually a big commitment since you can quit at any moment and start work. If you find that the benefit of what you're learning is less than the cost of fees and missed wages then just take a break and start work.
But while you look for a job, you may as well start uni and see what it's like. That way you'll not have the fear of missing out.
12  Game Development / Performance Tuning / Re: Interesting talk from Cliff Click, Azul Systems on: 2016-03-30 19:21:49
Something interesting which you're probably already aware of is that Azul systems have the best garbage collector (GC) that there is, it takes far less time in total and runs for shorter times than any Sun/Oracle GC.

It surprises me how impressive Sun and Oracle's work is on the JVM yet they give it away for free and Sun obviously struggled to monetise the technology. Even Oracle appear to have bought java just to sue Google for using the java API in android.
Meanwhile, Azul makes a single GC improvement and patents the idea, and then is able to sustain what looks like a very successful business. It's bizarre how things work out.
13  Game Development / Performance Tuning / Re: Interesting talk from Cliff Click, Azul Systems on: 2016-03-30 15:10:45
It was interesting at the end when he mentioned the 'register allocator' and if I heard correctly, speculated that the JVM could deliver a further 5% speed boost with this.

I find it hard to believe that there are few big improvements left to be made in the JVM. Seems like there's always more that can be done.
14  Games Center / WIP games, tools & toy projects / Re: Tetradecagon on: 2016-03-27 00:37:46
There's always more work that can be put into any game. In my opinion the bigger danger is to polish a game that no-one actually wants to play, wasting lots of the developer's time. If the game were released earlier, then it can be modified in response to audience feedback.
In many ways Brynn has done the right thing: release early, release often. Since he's gauging public opinion already, he knows what is missing and can be improved. Perhapshe will take it onboard, or perhaps he will be inspired to make a new project. Either way I don't think that there's a problem.
The game looks good by the way, very arcade-like.
15  Discussions / General Discussions / Re: Power consumption of desktops vs ARM SOC's such as Odroid-C2 or Rpi3 on: 2016-03-23 14:05:40
That's interesting how the server VM makes such a big difference.
Apparently tiered compilation is in OpenJDK:
I'll try it tomorrow and report back any speed differences.

Sounds like a nightmare with the GPIO. Being a cutting-edge new computer I can imagine that you might be the first person running into these troubles.
Can you hook up the pins manually somehow? Perhaps light them up with LED's or something to figure out how the layout has changed from the Rpi2 to the Rpi3.

I've wasted lots of time too. But most of my troubles are with linux and drivers. I have to reset my NetworkManager ubuntu app every 15 minutes to keep my usb wifi dongle working. I still haven't found a solution for it, and the wifi dongle was purchased with the odroid-c2 along with the linux distro so you'd think they'd have made sure it was compatible.
16  Discussions / General Discussions / Re: Power consumption of desktops vs ARM SOC's such as Odroid-C2 or Rpi3 on: 2016-03-23 13:42:54
OpenJDK is running the server VM, and since it's linux I don't think there is a client version.
I also believe that there's no special client or server version of the oracle embedded jdk either, but maybe I'm wrong.
EDIT: Oops, the oracle jdk says it's an embedded client version. But I see no server version on the oracle download page.

Here are the System.getProperty() dumps for each.

OpenJDK: SE Runtime Environment, sun.boot.library.path=/usr/java/jdk1.8.0_73/jre/lib/aarch64, java.vm.version=25.73-b02, java.vm.vendor=Oracle Corporation, java.vendor.url=, path.separator=:, HotSpot(TM) 64-Bit Server VM,,,, sun.os.patch.level=unknown, Virtual Machine Specification, user.dir=/home/odroid/Desktop, java.runtime.version=1.8.0_73-b02, java.awt.graphicsenv=sun.awt.X11GraphicsEnvironment, java.endorsed.dirs=/usr/java/jdk1.8.0_73/jre/lib/endorsed, os.arch=aarch64,, line.separator=
, java.vm.specification.vendor=Oracle Corporation,, sun.jnu.encoding=UTF-8, java.library.path=/usr/java/packages/lib/aarch64:/lib:/usr/lib, Platform API Specification, java.class.version=52.0, 64-Bit Tiered Compilers, os.version=3.14.29-37, user.home=/home/odroid, sun.arch.abi=gnu, user.timezone=, java.awt.printerjob=sun.print.PSPrinterJob, file.encoding=UTF-8, java.specification.version=1.8, java.class.path=.,, java.vm.specification.version=1.8,, java.home=/usr/java/jdk1.8.0_73/jre,, user.language=en, java.specification.vendor=Oracle Corporation, awt.toolkit=sun.awt.X11.XToolkit, mode, java.version=1.8.0_73, java.ext.dirs=/usr/java/jdk1.8.0_73/jre/lib/ext:/usr/java/packages/lib/ext, sun.boot.class.path=/usr/java/jdk1.8.0_73/jre/lib/resources.jar:/usr/java/jdk1.8.0_73/jre/lib/rt.jar:/usr/java/jdk1.8.0_73/jre/lib/sunrsasign.jar:/usr/java/jdk1.8.0_73/jre/lib/jsse.jar:/usr/java/jdk1.8.0_73/jre/lib/jce.jar:/usr/java/jdk1.8.0_73/jre/lib/charsets.jar:/usr/java/jdk1.8.0_73/jre/lib/jfr.jar:/usr/java/jdk1.8.0_73/jre/classes, java.awt.headless=true, java.vendor=Oracle Corporation, file.separator=/, java.vendor.url.bug=,, sun.cpu.endian=little, sun.cpu.isalist=

Oracle embedded JDK: SE Embedded Runtime Environment, sun.boot.library.path=/usr/java/ejdk1.8.0_73/linux_armv6_vfp_hflt/jre/lib/arm, java.vm.version=25.73-b02, java.vm.vendor=Oracle Corporation, java.vendor.url=, path.separator=:, HotSpot(TM) Embedded Client VM,,,, sun.os.patch.level=unknown, Virtual Machine Specification, user.dir=/home/odroid/Desktop, java.runtime.version=1.8.0_73-b02, java.awt.graphicsenv=sun.awt.X11GraphicsEnvironment, java.endorsed.dirs=/usr/java/ejdk1.8.0_73/linux_armv6_vfp_hflt/jre/lib/endorsed, os.arch=arm,, line.separator=
, java.vm.specification.vendor=Oracle Corporation,, sun.jnu.encoding=UTF-8, java.library.path=/usr/java/packages/lib/arm:/lib:/usr/lib, Platform API Specification, java.class.version=52.0, Client Compiler, os.version=3.14.29-37, user.home=/home/odroid, sun.arch.abi=gnueabihf, user.timezone=, java.awt.printerjob=sun.print.PSPrinterJob, file.encoding=UTF-8, java.specification.version=1.8, java.class.path=.,, java.vm.specification.version=1.8,, java.home=/usr/java/ejdk1.8.0_73/linux_armv6_vfp_hflt/jre,, user.language=en, java.specification.vendor=Oracle Corporation, awt.toolkit=sun.awt.X11.XToolkit, mode, java.version=1.8.0_73, java.ext.dirs=/usr/java/ejdk1.8.0_73/linux_armv6_vfp_hflt/jre/lib/ext:/usr/java/packages/lib/ext, sun.boot.class.path=/usr/java/ejdk1.8.0_73/linux_armv6_vfp_hflt/jre/lib/resources.jar:/usr/java/ejdk1.8.0_73/linux_armv6_vfp_hflt/jre/lib/rt.jar:/usr/java/ejdk1.8.0_73/linux_armv6_vfp_hflt/jre/lib/sunrsasign.jar:/usr/java/ejdk1.8.0_73/linux_armv6_vfp_hflt/jre/lib/jsse.jar:/usr/java/ejdk1.8.0_73/linux_armv6_vfp_hflt/jre/lib/jce.jar:/usr/java/ejdk1.8.0_73/linux_armv6_vfp_hflt/jre/lib/charsets.jar:/usr/java/ejdk1.8.0_73/linux_armv6_vfp_hflt/jre/lib/jfr.jar:/usr/java/ejdk1.8.0_73/linux_armv6_vfp_hflt/jre/classes, java.vendor=Oracle Corporation, file.separator=/, java.vendor.url.bug=,, sun.cpu.endian=little, sun.cpu.isalist=

Any news on your raspberry pi 3?  Cool
17  Discussions / General Discussions / Re: Power consumption of desktops vs ARM SOC's such as Odroid-C2 or Rpi3 on: 2016-03-23 13:11:26
Gahh, problem solved. Sorry for the multiple posts.
I needed to install the embedded headful version of the jdk which wasn't listed on the regular Java SE downloads page. The embedded jdk is on its own special page for some reason, here:

Interestingly, the oracle embedded jdk is slower than openjdk when running my little java2d pathfinding and lighting demo Huh

java-8-openjdk-arm64 (8u73) runs at about 55fps.
ejdk1.8.0_73/linux_armv6_vfp_hflt (8u73) runs at about 35fps.

Here is a break down of how long the updating (pathfinding and lighting calcs which involve some Math.sin functions), rendering (using java2D) and sleep (System.sleep(1)) take with each jdk.
You can see that the update is much faster on openjdk (2.1ms per frame) compared with the oracle embedded jdk (8ms per frame). The rendering is faster too, but the sleep is the same.

CodeTimer : mean period = 17.0901ms (count = 293, time = 5007.4107ms)
    update    12.31%    2.1037ms (count = 293, time = 616.3806ms)
    render    80.09%    13.6876ms (count = 293, time = 4010.4525ms)
    sleep     7.6%      1.2989ms (count = 293, time = 380.5777ms)

CodeTimer : mean period = 27.2585ms (count = 184, time = 5015.5651ms)
    update    29.37%    8.0067ms (count = 184, time = 1473.2273ms)
    render    66.51%    18.1293ms (count = 184, time = 3335.7976ms)
    sleep     4.12%     1.1225ms (count = 184, time = 206.5402ms)

I wonder how the open jdk can be faster than oracle's embedded version? Strange
18  Discussions / General Discussions / Re: Power consumption of desktops vs ARM SOC's such as Odroid-C2 or Rpi3 on: 2016-03-23 12:20:25
I tried including the option -Djava.awt.headless=false on the command line when I run java and now I get an:
UnsatisfiedLinkError: Can't load library: /usr/java/jdk1.8.0_73/jre/lib/aarch64/
19  Discussions / General Discussions / Re: Power consumption of desktops vs ARM SOC's such as Odroid-C2 or Rpi3 on: 2016-03-23 12:08:49
I have a 'java.awt.HeadlessException' problem with the Oracle ARM 64 JDK. The The OpenJDK version runs fine, no headless exceptions.
I installed Oracle JDK 8u73 "Linux ARM 64 Hard Float ABI" from their downloads page on to my odroid c2 and tried running my Java2D app that uses Swing/AWT and I got a HeadlessException.
Here's the page where I downloaded the jdk:

The odroid is a 64-bit ARM computer running Ubuntu, and I know it's hard float since this directory exists: /lib/arm-linux-gnueabihf.
When I print System.getProperties() I see that java.awt.headless=true. Does anyone know how to fix this?
I notice that the 64-bit ARM jdk is only 74MB but the x64 version is 152MB. It made me think that the missing MB's are the missing AWT and Swing files. But when I look in look at rt.jar it shows that the javax.swing classes exist  Huh

I found this related post that our very own @Cas has answered:
But it's still a mystery to me how that person downloaded the headful jdk.
If I did download the headful version, then why does the jvm think it's headless?

Of course my odroid computer is not headless, I'm looking at the desktop on my TV.

Thanks for any pointers  Smiley
20  Discussions / General Discussions / Re: Power consumption of desktops vs ARM SOC's such as Odroid-C2 or Rpi3 on: 2016-03-20 17:27:13
I received my odroid c2 in the mail!
I ordered it with a fancy emmc storage chip which is supposed to run faster than an SD card. It came pre-installed with Ubuntu 16.04 based on Kernel 3.14LTS installed with the MATE desktop.
It booted up quickly, and I was able to plug it into my TV using the HDMI port, and my mouse also worked straight out of the box which was a pleasant surprise.
The wifi usb antena I bought from the same company didn't work straight away unfortunately. It took a while to fix, and I'm not sure what fixed it exactly since I had to restart multiple times, plug in an ethernet cable, update ubuntu and the linux kernel and repeat before the wifi dongle would work. Even now it seems to drop out randomly, but I haven't investigated fully. Perhaps I'm missing another driver.
I wish the linux installation was stock ubuntu with unity rather than MATE, it would have made it easier to google for solutions to my problems.
One annoying thing is that everytime I shut the computer down, the time is reset to when I first booted it up. I'm not sure if this has something to do with the ordoid c2 not having a real time clock (RTC), or if it's a problem that I made when I updated the linux kernel or something else. It's quite annoying since the youtube website won't work in the Chromium browser, it complains that the https connection is corrupted. Fortunately the time updates itself using the internet after a minute or two and then everything is fine until the next time I boot up.

The system is faster than I expected and usable as a desktop, but I wouldn't call it fast. There appears to be about a half second delay before seeing any window after opening an app. I'm not sure if this is because the GPU has no drivers installed yet, or if it's because the 2Ghz processor is slow. Hopefully it's a GPU issue, which is supposed to be fixed in April:
"Ubuntu/Linux Mali GPU driver works only on the fbdev at this moment. X11 Mali drivers will be available in March or April."

The chromium browser works well, but the page loading is slow enough that I can see the css reflow the page as it loads jgo, for example. Unfortunately youtube videos on default HD 1080p settings are choppy with pauses every few seconds, but when I changed the youtube quality to 360p it ran fine. Apparently this slowness is due to the above issue of the VPU or GPU not having drivers yet.
Firefox 64bit bugs out and crashes though this is a known issue with the odroid c2, see the 'side notes' here:

Open JDK was pre-installed, so I tried running my old java2d apps. Unfortunately they immediately threw this error, but it was an easy fix by commenting out a line in a java properties file.

The little ordoid c2 ran my java2d-rendered lighting and pathing project ( in software quite well, painting the small 480x480 window at about 55fps using java 8 openjdk arm 64. I haven't tested on oracle's arm java version yet.
This compares to 250fps on my windows i7 laptop (hp dv6 7029tx) running oracle jdk Using the java2d trace option (-Dsun.java2d.trace=log) I can see that the rendering is all done in software (java2d.loops) too so the results are somewhat comparable. I'll have to try running it with oracle java on the odroid rather than openjdk.

21  Discussions / General Discussions / Re: Interesting proposals: Java 9 and beyond on: 2016-03-16 14:57:36
Isn't widespread use of instanceof seen as an anti-pattern?
22  Discussions / General Discussions / Re: Power consumption of desktops vs ARM SOC's such as Odroid-C2 or Rpi3 on: 2016-03-16 13:51:26
That's interesting about the Picaxe, I'd never actually heard of it before or knew that these micro controllers were easily programmable. Looks like they can do quite complicated and funny things:
But connecting to wifi sounds like a nightmare:

It's true that the odroid-c2's 2Ghz quad core CPU with 2GB RAM is overkill to turn on a sprinkler switch, but it was the only way my small brain could think of making it switchable remotely using a web browser on my mobile phone or a computer at work. I grow a few fruit trees like figs, mulberries, oranges and in the hot summer they will die if I leave them unwatered for a weekend while I'm away. I could buy an automatic electronic system for about $80 that is pre-programmed but it's actually not much cheaper than the odroid-c2 SOC ($80), a USB controlled relay (<$20), and a solenoid valve (<$30).
The other thing is that water here is relatively expensive at $2.2/kL and it takes 1.5kL to irrigate the plants on a hot day. Using the remote-controlled odroid-c2 computer I can water when it's needed, whereas a pre-programmed irrigation controller is more likely to over-water on days when it's raining and unnecessary.
Also with these flexible SOC computers, it's possible to hook up a weather station accessory, and maybe even a camera that uploads video or image stills to my server as a security record. But in reality I'll probably never get around to doing these extra things.

Certainly lots of great hardware out there for those that want to tinker with computer DIY.
It's an exciting new field with such cheap and powerful electronics.
23  Discussions / Miscellaneous Topics / Re: Go has been cracked! on: 2016-03-13 12:42:39
The hero of the meat heads strikes back:
24  Discussions / Miscellaneous Topics / Re: What I did today on: 2016-03-11 23:20:08
Got my next SAT scores back. 2050. Pretty f**king bummed because I studied ridiculously hard and it's still 200+ points under what I need for the universities I want to go to.

Doesn't particularly help that there's all these cunts waving around their 2250+ scores in my face.
Don't worry, practice makes perfect.
With these multiple-subject tests it seems like they favour generalists much more than specialists such as programmers like us who tend to be very good at logic and maths but poor at writing and literature. This is because it's easier to improve your score in below average subjects per unit of time invested than in above average subjects. So people who are Jack of all trades but masters of none tend to score better overall. The downside is that these people may not excel in their subject specialty since they don't have the in depth skill or passion for it.
Also, remember that bill gates and many other highly successful entrepreneurs dropped out of university or never made it in the first place.
25  Discussions / General Discussions / Re: Power consumption of desktops vs ARM SOC's such as Odroid-C2 or Rpi3 on: 2016-03-11 22:13:18
One advantage that the RaspberryPI now has over other boards is that it has a driver for running the full desktop OpenGL 2.0 on it (as opposed to just OpenGL ES), should make porting stuff to it much easier.
That's interesting, I didn't realise that difference.

Also that it has a bigger community, better documentation and so on.
Very true, and actually there's a silly bug or deficiency in the odroid c2 Ubuntu drivers where videos are played using software rendering rather than the GPU, making them run very slow on Ubuntu, however on Android this doesn't happen, they run in hardware. Hopefully this is fixed, but with the smaller community, maybe not.
26  Discussions / General Discussions / Re: Power consumption of desktops vs ARM SOC's such as Odroid-C2 or Rpi3 on: 2016-03-11 16:59:14
Oh thats great. i'd like to get an rpi3 too, but the price is very high at the moment on eBay.
Here's an interesting benchmark comparing the performance of an rpi1 and 2 against some desktops by running Doom and quake. I wonder how fair this is considering that these games were optimised for desktop. I also wonder how the rpi3 or odroid ç2 compare

PS: the odroid c2 CPU is 2ghz quad core arm 8 so the processor speed is comparable to a desktop, unless I'm missing something
27  Discussions / General Discussions / Power consumption of desktops vs ARM SOC's such as Odroid-C2 or Rpi3 on: 2016-03-11 15:51:11
I bought an Odroid-C2 which will be delivered in a week or two. It's a pretty impressive piece of hardware for the price:
It's very similar to the recently released raspberry pi 3:

I also ordered a USB-controlled relay board with the hope to build an automatic sprinkler system with solenoid valves to water my plants!

I've never dealt with electronics so this is quite exciting. I was surprised at how cheap the components are. I also never guessed that 240 volts could be controlled by a little USB connection.
I'm going to try to setup my Odroid-C2 as a ubuntu home server that will control my garden irrigation system solenoid valve using the usb-relay, which can hopefully be controlled by my ramnode VPS using a web page accessed by my phone. Apparently java 8 runs on the odroid and there's a few java libs to control the USB signals. It's going to be a fun project.

Something that's interesting is how little power these little ARM computers use compared to desktops.
I was weighing up buying an ARM system-on-a-chip (SOC) Odroid-C2 which costs about AUD150 with a memory card, versus an old ordinary headless desktop which costs AUD80 such as this HP DC5800:

I was about to buy the desktop rather than the ARM SOC because the desktop would be easier to use and space wasn't a problem. But when I compared the power usage, the ARM computers are so much cheaper to run.
Apparently the HP DC5800 desktop  above with Core 2 Duo E8400 uses 100W on idle and 140W on load, both without the monitor or graphics card:

While the Odroid-C2 ARM computer uses 1.8W on idle and 4.4W on load. But I'm not sure if this is using it's GPU or other components:

I calculated the power consumption for a 1 Watt device using my power cost in Australia at AUD0.22 per kWh:
Input: Cost of electricity in dollars per kilo Watt hour: 0.22 $/kWh
Input: Power required by device in Watts: 1W
The number of mega joules per kilo Watt hour: 3.6 MJ/kWh
Cost of electricity in dollars per mega Watt: 0.061111111 $/MJ
Power required by device in mega Watts per hour: 0.0036 MJ/h
Cost of electricity to power device in dollars per hour   : 0.00022 $/h
Cost of electricity to power device in dollars per day: 0.00528 $/day
Cost of electricity to power device in dollars per year   : 1.9272 $/year
I think I've done the calculations right since they're similar to this:

Therefore the Odroid C2 running at full load will cost about $8/year (=4.4W*1.93$/yr). While the HP DC5800 desktop would cost about $269/year (=140W*1.93$/yr).

That's quite a big difference. I had no idea that a desktop computer costs so much to run continuously as a home server, especially considering that this annual cost is more than 3 times the price of the machine itself.

I'd be interested to hear your thoughts about power consumption and the ARM computers such as the Odroid-C2 or Raspberry pi 3  Cool Smiley

28  Discussions / Miscellaneous Topics / Re: What I did today on: 2016-03-07 02:28:17
However the uni's i worked at in the EU didn't have the English speaking uni scams of the professes textbook being the course book or his buddies. Some of my engineering books were over $200. I just went for old editions that where fine. They really didn't change anything.  
Haha, yes that's prevalent in Australia too. Another trick they use is to take a US book and 'Australianise' it with a handful of new questions or case studies, and then become a joint author and make the students buy that odd new version, making more money for the new author and the publisher.

Long story short it was always easier to use copyleft or free as in beer text books and resources for the class.
Free textbooks are pretty hard to find in my subject area which is business. Of course that makes sense, why would a business-minded person give away things for free? Lol.
But I think that a project to make an opens-source textbook, modeled on the wiki community, would be very useful for many teachers and students. I haven't heard of any successful endeavor in the business subject area yet.

Statistical genetics, plain statistics, Bayesian statics, MCMC methods, population genetics, and Public DNA databases and how to not be bad on computers. Also some plain CS stuff.
Interesting subjects. Have you thought about taking a casual teaching job in Auckland for cash flow while you start your exciting business? I do some casual tutoring in Sydney and it helps pay the bills. 'Data scientist' skills are in vogue these days so your subject area will probably be in demand for competent teachers.
29  Discussions / Miscellaneous Topics / Re: What I did today on: 2016-03-06 18:00:16
it is often easier for us to grasp when you use actual numbers in an example to show where they are inserted into the formula and what the result should be.
Thanks for the feedback! I will definitely add more examples with actual real numbers.

they always have to start again rather than edit the existing text, due to copyright restrictions or because the author didn't provide their source document or because it's in an incompatible format.
I'm not entirely sure what you mean by that...Text should not be something modular like a Java class Smiley but highly integrated and well-structured, where every paragraph logically follows on its predecessor, to keep the "read flow." Little changes to something can then lead to a complete restructuring of the whole text, yes.

I agree that nicely crafted paragraphs are good. But look at the success of wikipedia where each article is written by hundreds of different people who sometimes disagree. Wiki articles contain lots of sub-headings that can address quite separate ideas relating to the article's topic. An open-source textbook constructed in this way would be very useful for students who can consume it, teachers who can take the parts of it that they want, and expert contributors who could add so much more than a single author making an ordinary textbook whose copyrights are sold to the publisher, leaving the material to languish without updates.
The current textbook situation is laughable at uni where publishers release a new book every year with the same end-of-chapter question, but the question numbers are switched-around just to make the old versions of the textbook unusable for students who must complete the set question numbers for homework. This forces students to buy a new text for $150. Also, to prevent electronic copying many publishers still only make texts available in paper form rather than pdf or web page form so students carry kilos of useless paper in their backpacks.
Sorry for taking this off-topic from your excellent book chapters, but I think it's an interesting issue.
30  Discussions / Miscellaneous Topics / Re: What I did today on: 2016-03-06 03:15:54
Okay, just finished the next 6 pages in which I try to explain how to derive the general sin/cos formula for angular vector rotation in 2D Cartesian coordinates, so that people understand what the whole rotate/rotation methods in JOML do. Learnt a lot myself and had to find a way to actually explain that stuff, since I never found a good explanation of that myself. Even the excellent book "Real-Time Rendering", 3rd ed. just gives the formula straight away on page 57 and never says, why this actually works.
Here is an excerpt:

It's well written. I'm very interested in learning that maths properly.
When you explain these concepts to noobs like myself, it is often easier for us to grasp when you use actual numbers in an example to show where they are inserted into the formula and what the result should be.

By the way, I'm always dismayed that whenever someone smart like yourself sees improvements that could be made to existing texts, they always have to start again rather than edit the existing text, due to copyright restrictions or because the author didn't provide their source document or because it's in an incompatible format.

I learn most maths theory from wikipedia which is a great source but they don't have enough worked examples. Unfortunately, people who try to add worked examples to wikipedia usually have their additions deleted by the wiki stasi since wikipedia is supposed to be an encyclopedia, not a textbook.
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