  A combined N--body/SPH code is presented which benefits from the high speed
of the special purpose hardware GRAPE (GRAvity PipE). Besides gravitational
forces, GRAPE also returns the list of neighbours and can, therefore, be used
to speed up the hydrodynamical part, too. After the interaction list has been
passed, density, pressure forces, propagation and interpolation of particles
etc. are calculated on the front end, a 50 MHz SUN SPARC 10. In order to
combine SPH and GRAPE, possible limitations due to the hardware design of GRAPE
are carefully analyzed and modifications compared to current SPH codes are
discussed. The resulting code, GRAPESPH, is similarly flexible as TREESPH. It
seems especially well suited to investigate the formation of individual objects
in a large scale structure environment, like eg. galaxies or clusters. The
total performance is at least half as good as treesph on a CRAY and for most
applications it seems to be even better. The CPU time per time step is only
slightly dependent on the clustering state. GRAPESPH, therefore, provides a
very attractive alternative to the use of supercomputers in cosmology.
