5,702 reputation
11333
bio website inspirehep.net/…
location Duchy of Grand Fenwick
age 43
visits member for 5 years, 5 months
seen 2 days ago

Experimental nuclear and particle physicist. These days I'm teaching, but I've spent a lot of time on nucleon structure in fixed target electron scattering and neutrino oscillations using reactors and beam sources.


Jan
20
comment Are there ASCII characters that have the same keyboard input for both PC and Mac?
You seem to be conflating concepts from several (many?) different levels of interpretation. Hardware, character set, OS level interpretation and program level interpretation. I think you need to be much more precise about what you are asking. Note, that almost all the ASCII characters use the same keystrokes on Macs and Wintel boxes, but that just the Latin alphabet, Arabic numerals a bit of punctuation and some control codes. Almost everything that you have to jump through hoops to enter is not ASCII.
Jan
12
comment Hardware/IO Bottlenecks
A poorly written piece of code will stall the pipeline over and over waiting for data to arrive from RAM. Nothing is getting done while that happens, so the code takes longer to finish. It really does affect the speed of a computation.
Jan
9
comment Hardware/IO Bottlenecks
The question is really ill-specified. It always depends on what you propose to do.
Jan
9
comment Hardware/IO Bottlenecks
RAM speed (as opposed to cache speed) matters a lot when you're doing medium sized computation. I've gotten a order of magnitude on occasion just be changing a program to make better use of the cache (matrix summation is a classic example of this kind of thing).
Jan
7
comment How do I log all UNIX shell commands submitted by all users?
I alert user would be able to disable this be resetting the variable and because it is executed "prior to issuing each primary prompt" this fact would not be logged.
Jan
6
comment Which malfunctions cause old computers to slow down and crash?
This would be somewhat enhanced by pointing out the importance of environment regulations against lead content: leaded solder doesn't do this, but to protect the water supply we either need to eliminate it (hard) or insure the proper disposal of all electronic kit (even harder).
Jan
6
comment Which malfunctions cause old computers to slow down and crash?
@Daniel: There are other types of capacitors which don't share all the failure modes of the electrolytic variety. So why do people use electrolytic ones at all: cost and availability---electrolytics are cheap, compact in the few millifarad to few farad range, and easy to get. I have no idea how much of an increment to expect.
Jan
6
comment Which malfunctions cause old computers to slow down and crash?
@Daniel: It should help.
Jan
6
comment Which malfunctions cause old computers to slow down and crash?
@petrus: That's my second link...
Jan
6
comment Which malfunctions cause old computers to slow down and crash?
Related: Why does hardware get slower with time?.
Jan
5
comment Ubuntu terminal characters required in Makefiles
I've had one more brain-storm: if you have unpacked onto a windows-native filesystem I'd look to see it tar or the filesystem might be diddling the line-endings for you. After that I'm stuck. The INSTALL file has a lot of advice further down, but it does require that you can guess at what's going wrong in the first place. Finally, do you have a non-VM environment you could try this in just for comparison?
Jan
5
comment Ubuntu terminal characters required in Makefiles
That pretty much shoots all my good ideas down, unless ./configure has missed something important.
Jan
5
comment Can computers be linked to work together?
So called "close-coupled clusters", of which Beowolf was the earliest example do function as a single, multiple CPU computer. Certainly the usual overheads apply, but they are distinct from the more common loosely couple clusters.
Jan
5
comment How to UNDO in Bash?
In addition to "Here's a nickle, kid. Get yourself a better computer." old unix programers and admins like to say "You recover from your backup. You do have a backup don't you?". Though in this case it is only the original contents of the sub-directory that are likely to be lost.
Jan
5
comment MacOS: How to “cd” into a symlink?
Well, you can create them...they just don't work.
Dec
30
comment Trying to start a GUI process on a second machine
The machine on which the program is going to be displayed must be running a X server (note that startx and similar scripts start the "server" in the X notation---the program that makes the screen available to "client"s like xclock, xeyes and so on). The machine where the code runs need not be running a X server. Finally, ave you checked that you have X forwarding enabled in ssh?
Dec
30
comment Trying to start a GUI process on a second machine
Right now I am unclear on what programs are running on which machines; what hardware is connected to each machine; and what shells are running (directly or by ssh) on which machines. So the advice below is necessarily general. If you want better advice you'll have to be very specific. Try listing the machines by name and purpose and telling us what shell you open on which machines.
Dec
17
comment Making a directory on unix readable,writeable,executable by me and no one else?
@ppuschmann: Yeah, that was pretty unclear. Is the edit better?
Dec
10
comment Linux less behavior and stderr
@cYrus: It occurs to me that the difference is probably the terminal we're using, as both my tests were in xterms (version 269) from the XQuartz 2.6.3. Indeed, the Mac OS 10.5 Terminal.app gets it "wrong" the first time then "right" subsequently. Huh? I guess that argues in favor of a buffering explanation, but I'm not going to try to figure it out any more.
Dec
10
comment Linux less behavior and stderr
Yeah, I opened a shell of Scientific Linux 5.3 box at work and got the expected behavior with bash 3.0.15 and less 382. Could there be a regression in there?