The de facto standard is that the standard BLAS/CBLAS functions take 32-bit integers in their API. Julia experimented with changing this so that they could use 64-bit integers in their main BLAS wrappers, and this worked great for a little while until they discovered that when people started trying to link in other existing BLAS-using code, this code was assuming that BLAS uses 32-bit integers and was causing segfaults. Their solution was to continue to use a 64-bit integer version of BLAS, but with symbols renamed to avoid collisions (so e.g. dgemm_ uses 32-bit integers, and dgemm_64_ uses 64-bit integers... [edited to get the 64-bit symbol names correct])

As mentioned in #37 (comment) , it would be great if a single BLIS library could export both 32- and 64-bit versions of these symbols simultaneously. It doesn't look like this would be too hard, since both the BLAS2BLIS interface is already generated using C preprocessor magic, and the CBLAS wrapper is already getting programmatically patched...