# Morning Session: Petaflop challenges

From ALPS

- Speaker&Chair: Thomas A. Maier "Petscale Computing"

- Discussions on talk
- Ten years from now: will technical aspects of petaflop computing be
**standardized**?- High diversity of algorithms/methods prevents standardization
- Large teams from different fields are required and actually growing over time
- Speedup of machines comes at a price of more complicated machines
- Even now, some applications are not run at teraflop scale

- Is there always a way to do
**in-situ data analysis**?- Filesystems scales to a few hundred nodes at most, even with HDF5
- Use small runs to explore physics, large-scale runs for big systems when questions are clear

- Is any method besides petaflop currently living on
**teraflop**?- Series expansion: possible
- Exact diagonalization: has been done
- Depends on Hamiltonian and geometry
- Use of symmetries
- Often O(N^2) communication tasks

- Tensor network states
- Terascale possible, petaflop still open
- Difficult linear algebra operations

- DMRG
- Many small matrices, high impact of communication latency
- Shared-memory very easy & efficient: linear scaling
- Huge matrix-matrix multiply
- Using GPUs can help a lot

- Which fields get most FLOPs at Oakridge?
- Material science, BEC
- Industry projects: BOEING
- Climate

- Ten years from now: will technical aspects of petaflop computing be