Friday, May 24th, 2013 at 4:56 pm - Adaptive
Believe it or not, I’ve been working on the Adaptive Clearing strategy recently, attempting to upgrade it to have multi-core capabilities. As you know, the free lunch was declared over 2005 when CPU clock-cycles stopped increasing exponentially. Now, instead, the numbers of cores are increasing. I have 8 cores on my current laptop, and when my state-of-the-art-algorithm runs on it using only 12.5% of the computing capability, it’s embarrassing.
To break the algorithm down into components that can be processed concurrently, I have separated it into 7 working threads, each of which pipes objects to the next layer through a queue. I was told that this is pretty standard architecture — even though it doesn’t look like it can be done using the concurrent.futures module in Python (where I looked for inspiration) because it looked like it needed the complete list of tasks before it could distribute them — at least in an earlier incarnation — and not a pipeline of data. I was also confused by the use of the word “futures” for processes not yet complete, which was similar to the __futures__ module which was features from a later version of Python into an earlier one. I don’t like the terminology anyway, but that’s just my opinion.
Anyway, a Queue is a structure that has functions queue.put(object) [to the front] and queue.get() [returns an object from the back], where each end can be handled by a different operator, like like this:
Let’s say op1 is sending in horizontal slices of the model (the objects obj) and op2 is calculating the clearing toolpath at each of the horizontal layers. We can run these two operations in different threads, and it will all work tickety-boo. The operating characteristics of the threads getting and putting from and into queues is that when a thread gets from a queue that it empty, it automatically sleeps (consuming no processor cycles) until something is put into the queue at the other end, at which point it automatically wakes up and retrieves the object. The opposite happens on the put if you have specified an upper bound for the capacity of the queue and you hit it.
Friday, May 24th, 2013 at 9:26 am - Cave
I have a confession to make. The digging trip in April wasn’t quite as boring as said.
In fact, we broke through. But since it would be about a month before the digging team could get back together and do all the stuff we needed to get done before the teeming hoards went in, we kept it secret.
To recap, the dig started in the dry mud floor in this terribly obvious place here:
Monday, May 20th, 2013 at 7:46 pm - Kayak Dive
I don’t usually talk about plans like this too far in advance, due to the fear of jinxing it by some bad event, but I am too much looking forward to this, and I don’t have anyone to go with yet.
Thursday, May 9th, 2013 at 1:57 pm - FOI
In their new executive-summary-style webpages, the UK Government sets out its case that it is fulfilling its side of the deal that allows them to remain a nuclear weapons state under the Nuclear Non-Proliferation Treaty wherein they promised to “pursue negotiations in good faith on effective measures relating to cessation of the nuclear arms race at an early date and to nuclear disarmament, and on a treaty on general and complete disarmament under strict and effective international control.”
Monday, May 6th, 2013 at 11:48 pm - Hang-glide
The Long Mynd hang gliding site is sort of on the way to LLandrindod Wells where we were going to bury grandfather’s ashes. He once owned a shop in Church Stretton nearby and talked about the gliders up on the Long Mynd in the early 1960s when he was out rambling. So it seemed like a good idea to go there and take advantage of the westerly wind.
Unfortunately at a wind-speed of 20mph, it was a bit breezy, so there were not many gliders there, even though it was a bank holiday. None of the pilots were local; the locals can pick better days when it’s going to be more fun. This was going to be a gale-hang. Two people had flown. Now it was my turn, having delayed until one of them had landed and could tell me the conditions (quite smooth).
Everyone had Wills Wing gliders similar to mine, not the fancy topless kind.
I had a good time — except for the landing. Actually, the landing was fine, it was the 3 seconds before it that weren’t so good. I should consult an instructor to work out what happened and whether the harness configuration needs thinking about.
I don’t know what I’m doing. At least the camera tells me my posture is terrible. You’re supposed to pull your weight sideways to turn the glider, but it looks like my legs go the other way half the time, which means I’m simply twisting and not shifting my weight anywhere. The picture shows me that the VG cord makes a difference to the flex of the wings, though I’m too insensitive to feel it because I can’t even tell the difference between turbulence and crap flying.
Also, this new flight computer doesn’t make much sense. I can plug it into an air speed indicator, and it thought I had already taken off due to the wind speed of 20mph, which was roughly the speed of the glider. When I pulled the bar in it could go up to 30mph.
The top graph shows that I immediately rode the rising air up to 350m above take off, then straight-away bombed back down before anything else happened. This coincided with my brief excursion north along the ridge in the right hand chart. Having lost all this height so quickly, and hated it, I hung out over the take off area for the rest of the flight, not wanting to risk going anywhere else again. A sailplane buzzed up and down the ridge below me. Much later another glider joined me, rising to my altitude in no time. It went along the ridge to the left and then back towards me, and was a lot more interesting to watch than my boring flight, according to Becka.
I want to go somewhere one day so I don’t just have map scribbles. But I don’t have the guts or the skill. I get all these notions when I’m on the ground, but it completely falls apart as soon as I take off. I’m sure there something obvious I’m missing out on. It’s like I’ve learnt the wrong shape of the air.
We stayed in a nice B&B on Saturday night, then in a not so nice hotel on Sunday night with the rest of the folks. Becka headed off early Monday morning for a scary caving trip in Pool Park with its heavy steel padlocked lid over a 100m entrance pitch (she dropped the padlock) on a nasty dry 9mm rope. Too scary for me. They call it a fear of heights, but it’s actually a fear of falling. The height is not a problem if you are flying, just as the depth of water doesn’t matter if you are floating. But if your hands are tied together and you are wearing lead ankle chains, then water gets really scary. I caught a lift to Cambridge for the day, and expect to be on a train home tomorrow night.
Here is a photo from out new local breadshop, the Baltic Bakehouse, which has opened about 2 blocks down the hill from us.
How things change from when we first got to Liverpool and there was nothing but Sayers the Bakers.
Blogging is limited due to effort being expended on an internal blog on the Qontext system in an attempt to annoy people who don’t know how to make a good interactive web system.
At night when I can’t sleep (most nights) I oscillate between reading the Dean Baker blog Beat the Press and the Paul Krugman blog Conscience of a Liberal. The repetitive hammering on at the same points over and over and over again until somebody gets it is comforting.
I particularly like the way Baker regularly appeals to “fans of arithmetic”. The Autodesk pension advisor recently got onto my case and I tried going over the arithmetic of his figures with him, only to find a 10% discrepancy. He says he’ll get back to me next week. Doing the figures raised more fundamental questions about the deal, such as why is it reasonable for their fee to be a percentage of the total saved rather than related to growth? Otherwise they get paid almost exactly the same if they happen to lose money.
So on Saturday we went digging in Rift/Large Pot as usual. Becka was there. I took my old Olympus Tough camera (because my new one has still not been fixed) and it ran out of batteries before I could take any photos of the progress in the dig. This was explained by a 20 minute long video of the inside of the tackle sack after it had been accidentally switched on. So here’s some photos of muddy people afterwards from the phone.
We won’t talk too much about the most effective stance for operating the kayak bilge pump used to drain the dig, except to say that you sit in the water, grip it between your thighs, and young men can go at it for quite some time. It’s surprising it still works after so much silt and mud has been sucked through it.
Later that evening, back at Bull Pot Farm, there was a cake competition.
This was more popular than the more normal photo competition, because it’s possible to bake an amazing cake in any oven, it doesn’t have to be a good one, and all cakes are good. Well, except for some of them. Sam’s Full English Breakfast cake with fried mushroom icing didn’t go down well, so it’s not a real cake. My contribution was a szechuan pepper treacle cake. I didn’t get a chance to taste much of it because after I had sampled everyone else’s cakes I was too caked out and wanted to eat a cabbage.
The next day, having consumed no more than 1.75 pints of weak ale the night before, I had a hangover that lasted till 9pm. I was quite grumpy as I tried to get some programming done in the cafe in Ingleton while Becka went down Rift Pot again to finish surveying the Chism Trail. Now the survey is complete, except a few metres of dig at the end, and the connection from Low Douk Pot that is being slowly blasted by dynamite. (You can smell the fumes in Rift.)
Today I had planned an attempt to go flying at Llangollen. But after a night of worrying and thinking about the stuff I needed to get done I bottled it. Some folks had a good day, according to the forums. Oh well. I got to get this work stuff out of my system and make time.
Friday, April 26th, 2013 at 12:35 pm - Kayak Dive
An excellent 3 days across and then underwater care of Aquaholics. The ferry departed at 10:30pm from about 5 miles away from our house, and the drive from Belfast to Ballycastle the next morning took under an hour, and then we were on the water.
The weather was excellent (after a week of dire forcast warnings so bad that we expected to get seasick on the crossing), but the viz was awful, even on the North Wall of Rathlin Island with its dropoff of 200m and where normal viz is 20 metres (it was about 3m for us).
Maybe its all that crap from the oil platform disaster in the Gulf of Mexico two years ago that’s finally worked its way up on the Gulf Stream. Not that there was much gulf stream in evidence as the water temperature was consistently 7 degrees C — a temperature not usually reached except on a few days in February. Something’s wrong.
But we had a great time. You can see me smiling underwater. I’ll be going again.
Sunday, April 14th, 2013 at 1:37 am - Kayak Dive
Have just finished a quick edit of the fun and games underwater with other divers and SMBs (surface marker buoys) on the Cornwall trip. I’m keeping up with the rate of new footage.
Last week I went into town to buy myself a logbook. I have been very slack for many years by not keeping a diving logbook. And I haven’t required a hang gliding logbook obviously, though that went AWOL towards the tail end of my activities. And it’s eccentric to keep a personal caving logbook, though there are usually club and expedition ones.
I thought maybe I’d do it if I made a combined one of everything. For a period I wrongly believed that the blog was sufficient. But the logbook records the names of who you went with, something that does not belong on the internet. So hopefully I’ll be able to keep it up this time. And continue to do stuff that requires logging.
In two entirely different places this week I have seen the world change. With the invention of a new machine tool architecture not based on the floppy cubical structure of all current machine tools that therefore need to be over-engineered to keep them together; and with the witnessing of a hand-held 50kHz distance measuring laser scanning device that renders obsolete the last 25 years of cave surveying I have participated in.
And I got a nice flight on my glider last Sunday. To be honest, I’d like a few more of those, and a little less of this world-changing nonsense, but that’s how it goes. It’s one reason I have never been very career ambitious, to the extent of locking in my advancement with positions of power or appointment. At all times I literally know what I’d rather be doing with my time.
Speaking of which, I notice that the CEO, about whom [I should steer clear of any references to --ed], has been sent to Coventry.
He’s giving a keynote at the Develop3D Live conference next Tuesday that happens to be in Coventry.
I’m half wondering about hopping over there next week and heckling from the audience. There’s this phone app I want to pioneer known as The Question From Hell. Originally I had targeted this idea at politicians, but it is actually CEOs who would be more entertaining.
I don’t have a Question From Hell for Carl right now, and even if I did I would probably try not to disclose it here, because you got to make it feel like it’s coming from Hell, and not from some guy you can possibly do something about when things have quietened down. The promise of revenge is a consolation at the time, however no one feels they can make revenge against Hell.
The App works in the following way:
Suppose I happen to be in the audience of some keynote presentation or panel discussion, where questions are taken from the floor, and Mr Bernard Charles, CEO of Dassault is speaking. So I text the name “Bernard Charles” to the Question From Hell phone number, and back it comes with the message:
Last May you told an audience that you were dropping Parasolid from SolidWorks. What’s the schedule for this development, and what are the technical issues that are stopping you from carrying this out?
My heart starts thundering like crazy for the next 20 minutes, which it does when I think I’ve got a good question for someone powerful and the opportunity to deliver it. If I haven’t passed out, or my feet haven’t gone cold, I stand up right away for the first question.
Mr Charles knows how to dodge the question, as one should expect, and the chairman knows how to move on and pick someone else in the audience for a second question to avoid the session being monopolized by this weirdo. Anyway, I can’t formulate a follow-up question, because I probably don’t even know what the hell Parasolid is, because I’m just someone reading the Question from Hell off their phone, so I can’t do a follow up question.
However, the text message goes out to anyone else in the audience who has done the same thing, advising them of the follow up questions, depending on the known dodges he’s going to do.
All of this has been crowd-sourced from insiders and experts close to the industry, even though today he thought he was simply giving a talk to a room full of school students.
When the Question From Hell system is going really well, there will be a whole industry of consultants able to take over the system and seed it with softballs, or those special non-melting snowballs that seem to last a long time in Hell.
Why don’t they just give us the list of questions worth asking on a sheet of paper at the door when we come in? The audience gets to pick the subject of the talk, so that’s fine. This would be in the spirit of total disclosure, like when you engage a legal representative and they explain to you in no uncertain terms that they expect you to tell them everything they should know about your involvement in the case, and that they will be extremely angry if they later find out something that you deliberately kept hidden from them.
This leads on to a slight improvement on the whole talk, presentation, speech, Q&A session tradition that we’ve got going here — which maybe I will try to put into action next time I am on the delivering end of one of these ceremonies. Take the last two minutes of your presentation to outline the range of interesting and difficult questions the audience could think about and ask you during the Q&A. Help them out a bit, and don’t leave them floundering.
It helps the poor chairman as well do their duty, because they are the ones left with thinking up a question to fill in the space in the event that everyone in the audience is sitting on their hands.