So, now you are in your working directory (say ATLAS/src/lapack), and you type make -f Make.ext, and nothing happens, no new files show up. This is because you need to re-extract your Make.ext file. This can of course be done by removing your whole ATLAS tree and reinstalling, but less brutally you can ``just'' use something like this: extract -b /home/soender/AtlasBase/make.base -o Make.ext rout=ATLAS/src/lapack -langM. The -langM switch is required for extract to properly handle makefiles, so you cannot skip it.
This is the basic procedure for this sort of stuff. When you need a makefile in a BLDdir subdirectory, the appropriate makefile is copied by Make.top from the ATLAS/makes/ directory. Check Make.ext to see which basefile they come from, and add your routine name among the names of the other routines.
Remember to update the Makefiles for both ATLAS/bin and ATLAS/src/testing, and to get these makefiles into the appropriate subdirs. In order to extract new makefiles, and get them put into the appropriate subdirs, I typically do something like (from the BLDdir:
pushd ~/TEST/ATLAS/makes/ ; make -f Make.ext ; cd .. ; \ make refresh ; popd(replace the path and arch appropriately, obviously).
Clint Whaley 2012-07-10