Posts by Christopher Lee

1) Message boards : The Lounge : The last to post at a secret date and time, wins (Message 28034)
Posted 15 Oct 2009 by Christopher Lee
The suspense is getting terrible
2) Message boards : The Lounge : The last to post at a secret date and time, wins (Message 27205)
Posted 9 Sep 2009 by Christopher Lee
Not a very active thread. Only 16 posts in over three months :-)


Still waiting for my spambot
3) Message boards : The Lounge : Analog(ue) computing: do we really need all those teraflops? (Message 26821)
Posted 27 Aug 2009 by Christopher Lee

I'm sorting out my bookshelves and, as usually happens, browsing is slowing the work down.

A book on analog(ue) computing (ref. below) reminded me of an old project. Can't really follow it now - it must be my brain that's slowed down. Anyway, I thought I'd write a note as the silly season is coming to an end.

Early analogue machines were mechanical; bombsights, gunsites and similar nasties were very sophisticated.

The technique became quite widespread with the introduction of electronics. Quantities are usually represented by voltages, all arithmetic functions are available, and you arrange to integrate and differentiate with respect to time.

Horrendously difficult differential equations, and more, solved for mathematical dummies while you watch.

An advantage for end users (as opposed to mathematiciens and programmers) is that implementations are relatively easy to understand as the problem is mapped more-or-less directly onto the hardware. Programmers didn't like it because of the hard-wiring, though you don't need to know much about electronics.

There was renewed interest in analogue computing in the 1970s, when the key component - the operational amplifier - became very inexpensive, and digital computers could be used for timing and to control the electromechanical control relays (hybrid computing). I used a very simple machine to model metabolic processes in different body compartments, and saw a big setup being used to model vehicle suspension systems. Digital computers were nowhere near powerful enough for that. Even now, you need a supercomputer or Boinc.

The technique seems to have died out, although with modern technology the main practical difficulties that drove us mad would exist no more: generating and recording arbitrary functions, accurate and inexpensive multiplication and division, relays and manual patchboards replaced by semiconductors.

The usable dynamic range of an operational amplifier is about 10e5 or 10e6; not too bad compared to some compilers still in use, but you did have to worry about scaling. Nowadays, this could be managed automatically by the digital computer.

Digital computing techniques are getting more and more powerful, and although analogue could be reconsidered at least for add-on accelerators, I don't suppose anyone would be interested in a change of mindset. Analogue computers were proprietary commercial products. A modern implementation would be no great challenge for an electronic engineer, who would perhaps use existing control and monitoring hardware and software (high accuracy, low noise and drift, but speeds as slow as you like). You need only a very limited set of hardware module types.

However, defining suitable (presumably open) hardware and software standards would involve some effort that may or may not be justified.

Perhaps someone brighter than me and with a bit of time to spare would like to review the subject, if only from the cultural/historical point of view.


Christopher R. Lee

Analogue and Iterative Methods in Computation, Simulation, and Control
Wilkins, B. R.
ISBN 10: 0412099608
ISBN 13: 9780412099601
Publisher: Chapman and Hall, 1970
Publication Date: 1970
Binding: Hardcover
Paperback 0412214202
Available secondhand from the usual sources.
4) Message boards : The Lounge : The last to post at a secret date and time, wins (Message 26820)
Posted 27 Aug 2009 by Christopher Lee
Can you tell me how to set up a spambot so I won't have to keep posting?
5) Message boards : Questions and problems : Facebook (Message 26497)
Posted 5 Aug 2009 by Christopher Lee
Despite Jord's warning I did manage to attach GridRepublic to Boinc (5.10.45) by following the instructions. It's still running OK.

Can I leave it like that to save the hassle of starting over?

In the long run, will this arrangement survive the inevitable software updates (apparantly I'm already out of date...)?

Finally (it may be another topic), you recommend we install a software security application. I'd like to know if GridRepublic / Boinc users make themselves more vulnerable than normal. The point may be important because life is already complicated for people who just want to use their computer. Potential volunteers may be dissuaded by recommendations to download what they could fear might become an unending stream of auxiliary applications.

6) Message boards : Questions and problems : Facebook (Message 26494)
Posted 5 Aug 2009 by Christopher Lee
I think I've sorted it out, even if Jord reminded us it is a beta.

My problem was that Facebook didn't make a tag or anything else visible on my wall or elsewhere. After a bit of messing around I found Progress thru Computers under (in French) Parameters - Applications, with some parameters you can set.

Managed to post the blue box on my wall and join the fan club; the buttons work OK.

7) Message boards : Questions and problems : Facebook (Message 26492)
Posted 5 Aug 2009 by Christopher Lee

I went to the Boinc link which provided some hoops to jump through to connect the existing application to facebook. Had to recover some passwords, of course!

Decided not to invite any friends for the moment and may not have clicked on the correct button.

Nothing on my wall after about half an hour, not even the promised badge - sob, sob. Boinc manager still indicates activity.

I guess we can expect some more user-friendly publicity and documentation shortly.

8) Message boards : Questions and problems : Facebook (Message 26488)
Posted 5 Aug 2009 by Christopher Lee
I've been running native Boinc for some time, and have just read about the Facebook interface.

This should be a Good Thing for attracting new volunteers.

The link provided goes straight into facebook and I don't want to activate this in case it messes up.

I know this is a very new development, but can we have a rundown on how to make the switch?


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