I have built octave 3.8.2 from source on Ubuntu 14.04 (LTS) using standard instructions. I have installed libblas-dev, liblapack-dev and libpcre3-dev. I have also used apt-get build-dep octave to resolve dependences. The build works and passes the tests.
I see that the resulting executable does not use multiple cores on an Amazon EC2 c3 16 core instance. I have the same experience installing 3.8.1 binary package on 14.04 LTS.
To contrast that, I have built octave 3.6.4 from source on Mac OSX 10.9.2 using fink. Upon using octave-atlas-364-dev, it can use multiple cores efficiently for standard dense matrix operations.
I would ideally like to use a tuned matrix library such as atlas for blas/lapack for octave 3.8.2. Any pointers / help is appreciated.