On the other hand, I’ve heard you talking about vectorising MATLAB programs to squeeze down your computation time…

For many of the things that I do it is the development time that is the limiting factor – how long will it take me to go from an idea in my head to something running on my machine?

Scripting languages such as Python or Perl (and also, for me, Mathematica and MATLAB) tend to be my weapons of choice for this very reason. My viewpoint is probably coloured by the fact that I tend to wrote lots of small demonstrations rather than enterprise level applications though.

Sorta, yes, but it’s more about what proportion of time in a ‘run’ is spent doing useful work.

Say for example you’re writing some code to run as a command line application to grab the content from a URL and write it to a file. You might expect the app to take a couple of hundred milliseconds to execute, so doing it in Java and incurring several hundred ms at to start would mean much more time taken starting the JVM than running the app.

On the other hand, if you’re writing the web application behind that URL, it’d make sense to be running already, waiting for requests. In this case, the startup time doesn’t matter so much, as you might spend days, weeks, months running, until you get shut down.

Somewhere inbetween, say you’re writing a command line app to do some complex processing to a load of scientific data. In this case, you’ll want something that can do your computation as quickly as possible and again, you’ll happily trade off a few hundred ms starting up for that runtime speed.