I just uploaded version 0.7 of the Haskell BLAS bindings! This is a major milestone– it is finally the library with all of the features that I want.

Here’s what the library is:

• It provides basic data types necessary for doing linear algebra. There are dense vectors and matrices, banded matrices, triangular and Hermitian dense matrices, and triangular and Hermitian banded matrices.
• It provides mutable types and operations that mutate them in either the ST or the IO monad.
• It maintains a clean distinction in the monadic functions between arguments that get mutated and arguments that get read. This allows passing immutable objects without calls to “unsafeThaw” everywhere.
• It gives a convenient interface to the Fortran BLAS functions. The emphasis here is on convenient. When using the Fortran functions directly, “dgemm”, the function that multiplies a dense matrix by another dense matrix, takes no fewer than 13 arguments. In the GNU Scientific Library, the binding for the function takes 7 arguments. The Haskell version takes 5.
• It uses BLAS calls internally to perform elementwise vector addition, subtraction, multiplication, and division, so these operations should be very efficient.
• It gives nearly complete access to all of the functionality in the Fortran libraries. The only missing functions for the dense matrix types are the are the matrix updating functions (ger, syr, etc.). Support for packed storage of triangular matrices is absent. Either of these would be a good project for anyone interested. Neither would be too difficult.
• Other than the matrix updated and the packed storage (and one other small thing, which I will talk about below), anything you can do in Fortran can be done in Haskell. Since most of the computation time in a numerical routine is in the floating point operations, this means that in principle you can write code in Haskell that will be just as fast the equivalent Fortran, at least for moderately-sized inputs.

Here’s what the library is not:

• It will never provide support for multiplication by the transpose of a complex matrix without making a copy. This is the missing feature hinted at above. Even though Fortran BLAS supports this, it is fundamentally impossible for the Haskell bindings. It is debatable how important this is, since multiplying by the conjugate of the transpose is supported.
• It is not a general array library. The only supported element types are Double and Complex Double. This will likely never change. If you want something general, use array, carray, uvector, or one of the thousand other Haskell array libraries.
• It is not a full-featured linear algebra library. You cannot compute an eigenvalue. You cannot perform a matrix decomposition. You cannot solve a linear system. This is a library for writing a full-featured linear algebra library. It is no good alone for doing anything substantial.

Interested in hacking? Please do. There is a list of project ideas in the TODO FILE. If any of these sounds worthwhile and you would like to work on it, let me know and I will give you some guidance.

Now that that’s out of the way, I can (finally) start LAPACK bindings.