Hello, Given that apparently HMatrix uses the same underlying representation as F arrays in REPA, I've wrote some utilities to convert to and from these types, and ported HMatrix functions to work with REPA arrays. http://hackage.haskell.org/package/repa-linear-algebra-0.0.0.0 All functions return F arrays. In general, unqualified functions take F array(s), and the postfixed functions take D array(s), allocating them before feeding to HMatrix: * -S functions allocate sequentially (using computeS) * -SIO functions allocate sequentially inside the IO monad (using computeIntoS) * -P functions allocate in parallel (using computeP) * -PIO functions allocate in parallel inside the IO monad (using computeIntoP) Writing all that boilerplate was quite mind-numbing, so sorry if there are any mistakes or inconsistencies (I wish this was a way to automate it, but it's not always straightforwards, for example I've decided that arguments that will be often supplied unchanged to multiple calls (like the kernel of convolution) shouldn't be changed to take D arrays in the preallocating functions). Please have in mind that the module is HIGHLY experimental, as it does just plain rude casts under the hood. Before you use it for anything serious first check if it works as you expect it to. Best regards, Marcin Mrotek