Monthly Archives: March 2011

“SuperMoon” Over Cardinia Reservoir

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So according to NASA:

Full Moons vary in size because of the oval shape of the Moon’s orbit. It is an ellipse with one side (perigee) about 50,000 km closer to Earth than the other (apogee): diagram. Nearby perigee moons are about 14% bigger and 30% brighter than lesser moons that occur on the apogee side of the Moon’s orbit.

Saturday 19th March was meant to be one such and whilst a difference of about 14% isn’t that much to the naked eye I thought it’d be interesting to try and get some photos of the moon anyway. I looked at Google Earth and saw that the moon would be rising over Cardinia Reservoir as seen from the wall of the dam, so that seemed a perfect spot to go. I’d already been there that morning for a walk and got this shot of the early morning sun over the water with my Nokia N900 cameraphone:

Early morning sun over Cardinia Reservoir

So that evening Donna and I headed over to the reservoir with cameras and a tripod and got some nice shots of both the sunset (using the Nikon D90’s “LiveView” mode to avoid looking through the viewfinder) and the “supermoon” itself.

Sunset from Cardinia Reservoir Sunset from Cardinia Reservoir

The "SuperMoon" through trees at Cardinia Reservoir "SuperMoon" over Cardinia Reservoir

The Ada Initiative’s Inaugural Census

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The recently formed Ada Initiative, a non-profit organization dedicated to increasing participation of women in open technology and culture, has been soliciting responses for their inaugural activity, a census of women in open technology and culture. The name is a little misleading as it is open for anyone to respond to, irrespective of gender, the idea being to get a feel of the communities perception of womens participation in this area of society. It’s very quick to take and I would encourage everyone who is involved in this area to participate.

Take the Ada Initiative Census

NUMA, memory binding and how swap can dilute your locality

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On the hwloc-devel mailing list Jeff Sqyres from Cisco posted a message saying:

Someone just made a fairly disturbing statement to me in an Open MPI bug ticket: if you bind some memory to a particular NUMA node, and that memory later gets paged out, then it loses its memory binding information — meaning that it can effectively get paged back in at any physical location. Possibly even on a different NUMA node.

Now this sparked off an interesting thread on the issue, with the best explanation for it being provided by David Singleton from ANU/NCI:

Unless it has changed very recently, Linux swapin_readahead is the main culprit in messing with NUMA locality on that platform. Faulting a single page causes 8 or 16 or whatever contiguous pages to be read from swap. An arbitrary contiguous range of pages in swap may not even come from the same process far less the same NUMA node. My understanding is that since there is no NUMA info with the swap entry, the only policy that can be applied to is that of the faulting vma in the faulting process. The faulted page will have the desired NUMA placement but possibly not the rest. So swapping mixes different process’ NUMA policies leading to a “NUMA diffusion process”.

So when your page gets swapped back in it will drag in a heap of pages that may have nothing to do with it and hence their pages may be misplaced. Or worse still, your page could be one of the bunch dragged back in when a process on a different NUMA node swaps something back in. This will dilute the locality of the pages. Not fun!

How computers fail to entice people into being programmers

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An old friend of mine from the UK, Steve Usher, has pretty much nailed things with this blog on “Enthusing teen minds: Why today’s computers won’t create tomorrow’s programmers“. He says:

The computers of the early 80s were a blank canvas. You plugged them in, switched them on and (hopefully) the input cursor blinked at you. There was no decoration, no clutter and it was something waiting for YOU to do something to it.

Ah yes, I remember those days, when 3.5KB was a lot of memory! But what about today’s computers ?

They’re immediately brimming full of functionality all vying for your attention, but it’s also incredibly locked down. You can do absolutely anything… ANYTHING as long as it’s what the visionary who steered the programming teams thinks that you should want to do. Woe betide you if you want to do anything different. It’ll either ignore you or give you an unhelpful suggestion in a dialog box. You can be creative, but only in the ways you’re told you can be.

But before us free software types get all puffy and “I told you so”, he points out that things aren’t that much better on our systems with all our SDK’s, IDE’s, toolkits, compilers and interpreters:

It’s like taking a 5 year old into an engineering workshop, sitting him down and then complaining when he doesn’t build a car as he had all the tools available to him to do it and hence it must be his fault.

I’m not as sure that we need to build something new from scratch though, I think it might be more the case that what we need to do is to sort through all the various projects that could fit what he is after and build a distro (of whatever OS) that boots up straight into that application and lets them play with it. Perhaps something like SDLbasic (a BASIC interpreter for game development) might be a good start ?

Garden photos – gluten free grains, bees and trees!

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Donna and I had a fun time yesterday gathering in our first harvest of gluten-free grains from the garden – buckwheat and millet. It only took half an hour or so to get that much from the small patches we’d planted so we were quite chuffed about it, and there is still more to come as you can see from the buckwheat flowers yet to set to seed and an ear of millet (one of many) still waiting to be colllected.

Our first harvest of millet and buckwheat from the garden Buckwheat flowers in our garden An ear of millet in our garden

Our bees also seem to be enjoying the good weather of this weekend, and I’m looking forward to a cooler one so we can check the hive to see how they’re doing with filling the top box with honey (there is a queen excluder between it and the rest of the hive so she can’t get up there to lay any brood into it).

An active beehive Busy bees Bee on lavender flower

All in all our garden is coming on really well, it’s a far cry from the boring old lawn – largely of the weed nutgrass – which we inherited!

A view down our garden By Gum!