blas-hs

blas-hs provides a complete low-level interface to Blas via the foreign function interface, allowing Haskell programs to take advantage of optimized routines for vector and matrix operations in Haskell. For more information about Blas, see http://netlib.org/blas

blas-hs is compatible with any library that implements the standard C interface for Blas. If your implementation does not provide a C interface or uses a nonstandard interface, consider installing the CBlas binding from Netlib: http://netlib.org/blas/blast-forum/cblas.tgz

Documentation is available on Hackage.

Take note of the versioning policy of this package.

Quick start

Before you install, be sure to read up on how linking is handled. The linking process is not fully automated and may require some manual intervention depending on your system configuration.

Since package is available on Hackage, it can be installed via cabal-install in the usual way:

cabal install blas-hs

Interface

The package provides two complete interfaces:

The Blas.Primitive.* modules expose the raw C interface. All functions are named in the same fashion as the original Blas interface with the cblas_ prefix removed. This interface is stable.
The Blas.Generic.* modules expose a slightly more sophisticated interface via type classes, allowing the functions to work on any of the 4 types supported by Blas. This interface is experimental.
The Blas.Specialized.* modules expose a more uniform interface similar to Blas.Generic.* but without any type classes. This interface is experimental.

Both of these two interfaces have Safe and Unsafe versions, of which the only difference is the type of foreign call used. Refer to the GHC documentation for more information regarding appropriate use of safe and unsafe foreign calls.

Requirements

blas-hs requires either the reference implementation of Blas from Netlib or any alternative implementation of Blas that is compliant with the de facto Blas interface (e.g. ACML, ATLAS, OpenBLAS, MKL, and many others). In addition, the implementation must supply a C interface (not the Fortran one). Fortunately, as long as the Fortran interface is available, one can use the CBlas bindings from Netlib to remedy this: http://netlib.org/blas/blast-forum/cblas.tgz

Linking to Blas

By default, blas-hs will link using -lblas. On Darwin or Mac OS X, blas-hs will instead use the Accelerate framework.

For any other configuration, you will need to tweak this process.

Note that linking blas-hs to the Blas library directly is optional: if you avoid linking while building blas-hs, then the linking is deferred to the user of the blas-hs library instead.

Predefined flags

The blas-hs.cabal file provides a set of predefined flags to cover a few of the common use cases. If you want to do something more exotic, you may need to edit the blas-hs.cabal file directly.

To override the default settings, you will need to give additional arguments to cabal-install:

cabal install blas-hs FLAGS...
# note: also works for `cabal configure`

Each flag is preceded by -f, so to turn on a flag named openblas, you would specify -fopenblas. To turn off the flag, specify -f-openblas instead.

The flags here are listed in order of precedence: each flag will override all preceding flags, so if you (for example) turn both openblas and mkl on, then mkl takes precedence. All flags are off by default.

no-netlib: Do not link with the reference Blas from Netlib.
no-accelerate: Do not link with the Accelerate Framework. Has no effect except on Darwin / Mac OS X.
openblas: Link with the OpenBLAS library.
mkl: Link with the Intel Math Kernel Library.

Additionally, there is also the cblas flag that can be used to link to the CBlas bindings, in case your Blas implementation doesn't provide a C interface. This flag may be used in conjunction with any of the other flags.

Custom configuration

In a more complicated situation, you will have to modify the blas-hs.cabal file. First, you need to figure out which libraries to link to, as well as any additional options that need to be passed to the linker. This usually comes as a set of command-line arguments. For example,

-fopenmp -L/usr/local/foobar/lib -lfoo -lbar

The exact meaning of the flags can be found in the manual of ld. For our purposes we only care about two kinds: those preceded by -l and those that aren't. The ones preceded by -l will go into the extra-libraries entry (without the -l prefix), while those that aren't will go into the ld-options entry.

Now it's just a matter of modifying the package.

Download the package:
```
cabal get blas-hs
```

Edit the blas-hs.cabal to add the custom configuration:

  -- custom configuration
  extra-libraries: foo bar
  ld-options:      -fopenmp -L/usr/local/foobar/lib

Change the current directory to that of the package, then run
```
cabal install -fno-netlib -fno-accelerate
```