![Convenient functions vs. efficient subroutines: Your choice](https://blogs.sas.com/content/iml/files/2017/01/AdvancedAnalytics-1.png)
I've pointed out in the past that in the SAS/IML language matrices are passed to modules "by reference." This means that large matrices are not copied in and out of modules but are updated "in place." As a result, the SAS/IML language can be very efficient when it computes with