Hi, There was a discussion few months ago where the problem of single precision f2cblas routines returning double precision values was fixed by creating a new f2cblaslapack package. However, the maint branch still uses f2cblaslapack-3.1.1.q.tar.gz where the signature is wrong: doublereal sdot_ and all that. The fix is in master, which uses f2cblaslapack-3.4.1.q.tar.gz. Perhaps maint should be updated? maint - https://bitbucket.org/petsc/petsc/src/fa9e63e24d90a9e99336ca74ae004b9b5f1da8... t=maint master - https://bitbucket.org/petsc/petsc/src/cee652cbe889c53a5c397ca74d3ef6fdcdf8b9... t=master Chetan