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PAPR is the Power Architecture Platform Reference document. It’s a short read at only 890 pages and defines the virtualised environment that guests run in on PowerKVM and PowerVM (i.e. what is referred to as ‘pseries’ platform in the Linux kernel).
As part of the OpenPower Foundation, we’re looking at ensuring this is up to date, documents KVM specific things as well as splitting out the bits that are common to OPAL and PAPR into their own documents.
Being involved with teaching young students to code, I have come to the tentative conclusion that many coding kids have not actually been taught programming. This has been going on for a while, so some of this cohort are now themselves teaching others.
I have noticed that many people doing programming actually lack many of the fundamental skills that would make their programs efficient, less buggy and even just functional.
A few years back, Esther Schindler wrote an article Old-school programming techniques you probably don’t miss (ComputerWorld, April 2009).
Naturally, many (most!) of the things described there are familiar to me, and it’s interesting to review them. But contrary to Esther, I still do apply some of those techniques – I don’t want to miss them, as they serve a very important purpose, in understanding as well as for producing better code. And I teach them to students.
Programming is about smartly applied laziness. Students are typically aghast when I use that word, which is exactly why I use it, but the point is that smartly applied laziness is not the same as slackness. It’s simply a juicy way of describing “efficient”.
Suppose you need to shift some buckets of water. You could carry one bucket at a time, but you’ll quickly find that it’s hard on your arm and shoulders, as well as wasting the other arm you have. So we learn that if you have more than one bucket to shift, carrying only one bucket at a time is not the best way of going about it. Similarly, trying to carry three or more buckets is probably going to cost more time than it saves, as well as likely spilling water all over the place.
Thus, and this was of course worked out many centuries ago, carrying two buckets works best and is the most efficient as well as being quite comfortable – particularly when using a neat yet simple tool called a yoke (as pictured).
Inevitably, most kids will have at some time explored this issue themselves (perhaps while camping), and generally come to the same conclusion and insight. This is possible because the issue is fairly straightforward, and not obscured by other factors. In programming, things are not always so transparent.
Our modern programming tools (high-level languages, loose typing, visual programming, extensive APIs and libraries) enable us to have more convenience. But that convenience can only be applied judiciously when the programmer has the knowledge and skills required to make appropriate judgements. Without that, code can still be produced rapidly, but the results are not so good.
Some would say “good enough”, and that is somewhat true – when you have an abundance of computing power, memory and storage, what do a few bytes or cycles matter? But add together many of those inefficiencies, and it does become a rather dreadful mess. These days the luxury of abundance has become seriously abused. In our everyday life using laptops, smart-phones, tablets and other devices, we frequently encounter the consequences, and somehow regard it as “normal”. However, crashing apps (extreme case but very common) are not normal, and we should not regard any of this as good enough.
I see kids being taught to code using tools such as MIT’s Scratch. I reckon that’s fine as a tool, but in my observations so far the kids are only being shown how the system works. Some kids will have a natural knack for it and figure out how to do things properly, others will plod along and indeed get through by sheer determination, and some will give up – they might conclude that programming is not for them. I think that’s more than a pity. It’s wrong.
When you think about it, what’s actually happening… in natural language, do we just give a person a dictionary and some reference to grammar, and expect them to effectively use that language? We wouldn’t (well actually, it is what my French teachers did, which is why I didn’t pick up that language in school). And why would computer programming languages be different?
Given even a few fundamental programming techniques, the students become vastly more competent and effective and produce better code that actually works reliably. Is such understanding an optional extra that we don’t really care about, or should it be regarded as essential to the teaching?
I think we should set the bar higher. I believe that anyone learning programming should learn fundamentals of how and why a computer works the way it does, and the various techniques that make a computer program efficient and maintainable (among other attributes). Because programming is so much more than syntax.
Dark narrow streaks, up to a few hundred yards long, are seen along many slopes on Mars including Garni Crater. The identification of waterlogged salts in these streaks fits with the idea that they are formed by the underground flow of briny water that wets the surface.
Proof-of-concept study shows possibilities for mind-controlled technology.
In the preliminary proof-of-concept study, led by UCI biomedical engineer Zoran Nenadic and neurologist An Do, a person with complete paralysis in both legs due to spinal cord injury was able – for the first time – to take steps without relying on manually controlled robotic limbs.
So this is using brainwave-detecting technology to reconnect a person’s brain with part of their body. A very practical example of how science can (re)enable people, in this case give them back their freedom of mobility. That’s fantastic.
Complementary, Honda’s ASIMO robot research can enable people to walk with artificial legs.
Don’t think this is just something that happens in labs! The basic tech is accessible. I have a single sensor EEG headset here, and some years ago I did a demo at a conference entitled “look ma, no hands” where I controlled the slide advance of the presentation on my laptop by doing a “long blink”.
[…] interactive flow chart for people who struggle with self care, executive dysfunction, and/or who have trouble reading internal signals. It’s designed to take as much of the weight off of you as possible, so each decision is very easy and doesn’t require much judgement.
Some readers may find it of use. I think it’d be useful to have the source code for this available so that a broad group of people can tweak and improve it, or make personalised versions.
So I finally managed to catch up with Chris Arnade and have a chat about his Faces of Addiction project last friday night. I don't think I was at my best (but, after a year off and the interview being at 11pm I'm going to cut myself a little slack).
I'll be putting the episode out this weekend and will let everyone know when it's up.
XKCD’s Randall nails it beautifully, as usual…
sure you can code around this particular “attack vector”, but there are infinite possibilities… these are things we do have to consider along the way.
This is something that I feel quite strongly about. Both of my parents have tried to commit suicide when I was young, at different times and stages of my life. The first one was when I was about 11 and I don’t remember too much about it, there was a lot of pain flying around the family at that time and I was probably shielded from the details. The second parent (by then long divorced from the other parent) tried when I was 21 and away at uni in a different city. That one I remember vividly, even though I wasn’t there.
My reactions to the second were still those of a child. Perhaps when it’s a parent, one’s reactions are always those of a child. For me the most devastating thought was a purely selfish one (as fits a child) “Do I mean that little to them? Am I not even worth staying alive for?” The pain of that thought was overwhelming.
At the time I was young, saw myself as an optimist and simply could not relate in any way to the amount of pain that would bring one to such an action. I was angry. I described suicide as “the most selfish act anyone could do”.
Now decades of time and a world of life experience later, I have stared into that dark abyss myself and I know the pain that leads one there. I know how all-encompassing the pain and darkness seems and how the needs of others fade. An end to the pain is all one wants and it seems inconceivable that one’s life has any relevance any more. In fact, one can even argue to oneself that others would be better off without one there.
In those dark times it was the certain knowledge of that pain I had experienced myself as one (almost) left behind that kept me from that road more firmly than anything else. By then I was a parent myself and there was just no way I was going to send my children the message that they meant so little to me they were not even worth living for. Although living seemed to be the hardest thing I could do, there was no hesitation that they were worth it.
And beyond the children there are always others. Others who will be affected by a suicide, no matter of whom. None of us is truly alone. We all have parents, we may have siblings. Even if all our family is gone and we feel we have no friends, it is likely that there are people who care. The person at the corner shop from whom you buy milk on weekends and who may think “should I have known? Is there anything I could have done?” Even if you can argue that there is no-one that would notice or care, let’s be frank, someone is going to have to deal with the body and winding up of financial and other affairs. And I’m sure it’s really going to make their day!
Whenever I hear about trains being delayed because of incidents on the track I am immediately concerned for those on the train, not least of all the drivers. What have they ever done to that person to deserve the images that will now be impossible to erase from memory, which will haunt their nights and dark moments and which may lead them to require therapy.
There are many people, working for many organisations, some sitting at telephones in shifts 24 hrs a day, who want more than anything else to help people wrestling with these dark issues. They care. They really do. About everyone.
Help is always available. So let’s all acknowledge that suicide Always causes pain to others.Need help?
The ArduPilot development team is proud to announce the release of version 3.4.0 of APM:Plane. This is a major release with a lot of changes so please read the notes carefully!
First release with EKF by default
This is the also the first release that enables the EKF (Extended Kalman Filter) for attitude and position estimation by default. This has been in development for a long time, and significantly improves flight performance. You can still disable the EKF if you want to using the AHRS_EKF_USE parameter, but it is strongly recommended that you use the EKF. Note that if an issue is discovered with the EKF in flight it will automatically be disabled and the older DCM system will be used instead. That should be very rare.
In order to use the EKF we need to be a bit more careful about the setup of the aircraft. That is why in the last release we enabled arming and pre-arm checks by default. Please don't disable the arming checks, they are there for very good reasons.
Last release with APM1/APM2 support
This will be the last major release that supports the old APM1/APM2 AVR based boards. We have finally run out of flash space and memory. In the last few releases we spent quite a bit of time trying to squeeze more and more into the small flash space of the APM1/APM2, but it had to end someday if ArduPilot is to continue to develop. I am open to the idea of someone else volunteering to keep doing development of APM1/APM2 so if you have the skills and inclination do please get in touch. Otherwise I will only do small point release changes for major bugs.
Even to get this release onto the APM1/APM2 we had to make sacrifices in terms of functionality. The APM1/APM2 release is missing quite a few features that are on the Pixhawk and other boards. For example:
that is just the most obvious major features that are missing on APM1/APM2. There are also numerous other smaller things where we need to take shortcuts on the APM1/APM2. Some of these features were
available on older APM1/APM2 releases but needed to be removed to allow us to squeeze the new release onto the board. So if you are happy with a previous release on your APM2 and want a feature that is in that older release and not in this one then perhaps you shouldn't upgrade.
While most people are happy with autotune to tune the PIDs for their planes, it is nice also to be able to do fine tuning by hand. This release includes new dataflash and mavlink messages to help with that
tuning. You can now see the individual contributions of the P, I and D components of each PID in the logs, allowing you to get a much better picture of the performance.
A simple application of this new tuning is you can easily see if your trim is off. If the Pitch I term is constantly contributing a signifcant positive factor then you know that ArduPilot is having to
constantly apply up elevator, which means your plane is nose heavy. The same goes for roll, and can also be used to help tune your ground steering.
This release includes a lot more options for diagnosing vibration issues. You will notice new VIBRATION messages in MAVLink and VIBE messages in the dataflash logs. Those give you a good idea of your
(unfiltered) vibration levels. For really detailed analysis you can setup your LOG_BITMASK to include raw logging, which gives you every accel and gyro sample on your Pixhawk. You can then do a FFT on the
result and plot the distribution of vibration level with frequency. That is great for finding the cause of vibration issues. Note that you need a very fast microSD card for that to work!
This is the first release that allows you to disarm using the rudder if you want to. It isn't enabled by default (due to the slight risk of accidentially disarming while doing aerobatics). You can enable it
with the ARMING_RUDDER parameter by setting it to 2. It will only allow you to disarm if the autopilot thinks you are not flying at the time (thanks to the "is_flying" heuristics from Tom Pittenger).
This release includes support for a bunch more sensors. It now supports 3 different interfaces for the LightWare range of Lidars (serial, I2C and analog), and also supports the very nice Septentrio RTK
dual-frequency GPS (the first dual-frequency GPS we have support for). It also supports the new "blue label" Lidar from Pulsed Light (both on I2C and PWM).
For the uBlox GPS, we now have a lot more configurability of the driver, with the ability to set the GNSS mode for different constellations. Also in the uBlox driver we support logging of the raw carrier phase and pseudo range data, which allows for post-flight RTK analysis with raw-capable receivers for really accurate photo missions.
Better Linux support
This release includes a lot of improvements to the Linux based autopilot boards, including the NavIO+, the PXF and ERLE boards and the BBBMini and the new RasPilot board. If you like the idea of flying
with Linux then please try it out!
On-board compass calibrator
We also have a new on-board compass calibrator, which also adds calibration for soft iron effects, allowing for much more accurate compass calibration. Support for starting the compass calibration in the
various ground stations is still under development, but it looks like this will be a big improvement to compass calibration.
Lots of other changes!
The above list is just a taste of the changes that have gone into this release. Thousands of small changes have gone into this release with dozens of people contributing. Many thanks to everyone who helped!
Other key changes include:
Note that the documentation hasn't yet caught up with all the changes in this release. We are still working on that, but meanwhile if you see a feature that interests you and it isn't documented yet then please ask.
German Hams Helmut and Alfred have been doing some fine work with FreeDV 700B at power levels as low as 50mW and SNRs down to 0dB over a 300km path. I thought it might be useful to show how SNR relates to Eb/No and Bit Error Rate (BER). Also I keep having to work this out myself on scraps of paper so nice to get it written down somewhere I can Google.
This plot shows the Eb/No versus BER for of a bunch of modems and channels. The curves show how much (Eb/No) we need for a certain Bit Error Rate (BER). Click for a larger version.
The lower three curves show the performance of modems in an AWGN channel – a channel that just has additive noise (like a very slow fading HF channel or VHF). The Blue curve just above the Red (ideal QPSK) is the cohpsk modem in an AWGN channel. Time for some math:
The energy/bit Eb = power/bit rate = S/Rb. The total noise the demod sees is No (noise power in 1Hz) multiplied by the bandwidth B, so N=NoB. Re-arranging a bit we get:
or in dB:
So for FreeDV 700B, the bit rate Rb = 700, B = 3000 Hz (for SNR in a 3000Hz bandwidth) so we get:
Now, say we need a BER of 2% or 0.02 for speech, the lower Blue curve says we need an Eb/No = 4dB, so we get:
So if the modem is working down to “just” 0dB we are about 2dB worse than theoretical. This is due to the extra bandwidth taken by the pilot symbols (which translates to 1.5dB), some implementation “loss” in the sync algorithms, and non linearities in the system.
I thought it worth explaining this a little more. These skills will be just as important to people experimenting with the radios of the 21st century as Ohms law was in the 20th.
Justin, VK7TW, has published a video of my recent presentation at Gippstech, which was held in July 2015. Good summary of FreeDV, the SM1000, and the exciting possibilities for VHF Digital Voice. Thanks Justin! Here are the Open Office slides of the presentation.