a function like foo :: (BLAS1 e) => Matrix (m,n) e -> Matrix (n,k) e -> Int -> Vector m e foo a b i = let x = row b i in a <*> x will not type-check. (”<*>” is the function to multiply a matrix by a vector. Everything is ok if you replace “row” by “col”.) This feature has caught a few bugs in my code.
If I understand this correctly, the compiler can catch dimension mismatches so that using `col' will result in a compilation error when m and k are different, is it so?
Yes, the compiler infers the type of expression to be Matrix(m,n) e -> Matrix (l,m) e -> Int -> Vector n e which is different from the declared type. The error will be something like "Expected type Vector m e, but got type Vector a1 e instead".
I haven't look through the code, yet. But it looks like there are certain levels of similarities between blas and hmatrix. Is it possible for these two libraries to cooperate well with each other? (I didn't look at HBlas, so can't say much about that.)
This is more work than you might think. The data structures are different, many of the function names are different, and the module namespaces overlap. I wouldn't recommend any switch from hmatrix to blas right now unless you really need mutable types-- hmatrix has a lot more linear algebra functionality.
Apart from some warnings, the library compiles fine in my system. But there is a minor issue about the library it links against when `./Setup test'. I need to use `-lcblas' instead of `-lblas' to get it to link to correct libraries. I don't know other people's system. But in my system, Gentoo Linux, I use blas library provided by atlas, and libblas.so is a fortran library and libcblas.so is for C.
I don't know of a good way to get around this. It seems like every system has a different convention for the location and name of the cblas libraries. So, everyone has to edit the "extra-libraries" and the "extra-lib-dirs" field in the blas.cabal file. Does anyone know of a better way of doing this? Patrick