Last summer, I played a bit with RF propagation modeling, hoping to determine whether low-power VHF radios would work for communications for the annual Gore Fest kayak race through Gore Canyon in Colorado. The local hams typically use something called Radio Mobile Online which seems to work pretty well but isn't open-source and requires an account to use. Instead, I've been using a tool called “SPLAT!" which is free under the GPLv2 and also seems to work pretty well once you get it setup. Read more

Something that has been annoying me for a while is OSX's X implementation's behavior when trying to paste into an Xterm. Using the usual hotkey doesn't paste as you'd expect (though, oddly, copy does work). After a perusal of the man page, it turns out this is rather easy to fix: Read more

Normally I'm not a fan of closed tools and even less a fan of closed file formats, but lately I've been struggling with some numerical code and the FOSS tools haven't been working well enough (which is a topic for another day). Simply put, I need something that does matrix arithmetic correctly and that is easy to manipulate/debug data structures in. I could use SciPy, but I've never liked Python and Matlab makes what I need trivial. Read more

My old (great, reliable – until it got wet) TomTom One series finally died a while back, and the android phone isn't cutting it in areas without cell coverage so I finally upgraded to a new Via series. Unfortunately, it refused to talk to OSX at first. The status icon would say “Connecting” and the right part number would show up in their web interface, but I was unable to associate the device with my account or add any updates. Read more

NMatrix is a Ruby library providing some linear algebra functions and sparse data-structures. Unfortunately, it's surprisingly difficult to get running on OSX. Here's a hackish method, using rvm and macports (I'll show what I had to install on my system, you may need more – the documentation is rather sparse at this point). sudo port install atlas cd rvm use ruby-1.9.3 gem install isolate hoe rspec rake-compiler hoe-git json packable git clone https://github. Read more

Apple's search indexer “Spotlight” likes to run and use all the disk bandwidth and most of the CPU on my machine quite regularly. It seems to correlate with large numbers of file changes, and can keep running for hours. For example, it can't handle doing a git checkout which changes a few thousand files. Backup programs which generate a large number of short lived temporary files also seem to incapacitate the indexer (for example, BackBlaze). Read more

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Tracing tools for executables are surprisingly hard to come by. Profilers are plentiful, but if you're willing to take the performance hit and want to see a complete, recorded, call tree your options are rather limited. In the HPC world, the “standard” is probably Tau, but it's a pain to integrate with non-trivial build systems and complicated to use. I also found a tool called “etrace” which uses a lesser known feature of gcc that adds a callback at each function entrance/exit ("-finstrument-functions”). Read more

If you deal with “enterprise” hardware at all, you're probably familiar with LSI's RAID controllers. Their stuff seems to generally work rather well, though the user interface could be improved. In any case, one of the machines I run with 12 disks on an LSI controller recently started exhibiting some unusual performance characteristics. For the most part things were working fine, but maybe once a week the system would slow to a crawl until it was rebooted or left alone for a few hours. Read more

I was asked today about how to log the output of a command on Linux. It turns out that there are a number of ways of capturing output in *NIX environments. The well known method is to make the shell take care of it, for example, if you use bash you could: echo "test" &>log.txt Unfortunately, this does have some limitations. It will capture standard output and standard error, but it won't (directly) capture any input from the user and it won't capture anything directly written to the pty by the program. Read more