It is in include/petsccusp.h but has includes from the PETSc source code tree (which won't even work for --prefix installs). Likely this need to be refactored or discarded or something #if !defined(__PETSCCUSP_H) #define __PETSCCUSP_H /* This should only be included in user code that uses CUSP directly and hence the file name ends with .cu */ #include <../src/vec/vec/impls/dvecimpl.h> #include <../src/vec/vec/impls/seq/seqcusp/cuspvecimpl.h> #endif