• It uses simple and fast memory management routines; it allocates all the needed memory at the starting time and borrows/returns a chunk of memory from/to the memory reservoir during the simulation run. All the information on memory requested by the client function is stacked in the list. We manage to alleviate the overload of memory movement/copy that occurs when it tries to realloc and free the memory chunk that resides in the middle of the memory stack in the reservoir.

  • It uses z-directional domain decompsitions; we decided to use this DD scheme because of the fftw which wants it. Also this kind of DD is very simple to implement.

  • It uses the FFTW of the parallel MPI version 2.

  • It adopts a dynamic DD with a variabel height equalizing the number of particles in each domain within sub % levels.

  • It uses Oct-sibling trees to correct short-range g-force; the Oct-sibling tree is a good choice to enhance the speed of the tree walks. A more advanced Oct-sibling tree and tree walking are adopted in the GOTPM-II and the resulting speed is about three times faster than the original one.

  • It uses particle-structure exchanages (for GOTPM-II only); The PM particle structure has 7 members (x,y,z,vx,vy,vz, indexing) and Tree particle structure has 8 members (x,y,z,vx,vy,vz,indexing, pointer). And the PM part needs additional memory similar in size to two members of each particle for the dynamic PM mesh and static fftw mesh. If not using the particle indexing, the GOTPM-II code needs 2.2 Terabytes for the 4096^3 particle simulation.

  • It does not use the force array (for GOTPM-II only) in order to reduce the memory overload. Temporal variables to save the forces measured in the PM/Tree are instantly applied to update the velocity of the particle and it is recycled for another particle.

  • 60 words for a particle info.
  • static DD in PM + dynamic DD in Tree

  • 32 words for a pm particle/40 words for a tree particle
  • dynamic DD in PM + dynamic DD in Tree

  • Any more information on the code can be also provided if requested.

    If more information is needed, please email to

    Korea Insititute for Advanced Study, 207-43 Cheongnyangni 2-dong, Dongdaemun-gu, Seoul, 130-722, Korea
    Fax: 82-2-958-3770