PaSTRI: A Novel Data Compression Algorithm for Two-Electron Integrals in Quantum Chemistry

Event Sponsor: 
Mathematics and Computer Science Division
Start Date: 
Aug 21 2017 - 10:00am
Building 240/Room 4301
Argonne National Laboratory
Ali Murat Gok
Speaker(s) Title: 
Northwestern University
Franck Cappello

Integral computations for two-electron repulsion energies are very frequently used applications in quantum chemistry. Computational complexity, energy consumption and the size of the output data generated by these computations scales with O(N4 ), where N is the number of atoms simulated in the system. In many applications, the same integrals are required to be calculated multiple times. Storing these values and reusing them requires impractical amounts of storage space; whereas recalculating them requires a lot of computations. On the other hand, generated data typically requires much less precision than the built-in floating point data types. We propose PaSTRI (Pattern Scaling for Two-electron Repulsion Integrals), a fast novel compression algorithm which makes it possible to calculate these integrals only once, store them, and reuse them at much smaller computational cost then recalculation. PaSTRI is “lossy” compared to floating point numbers, but still maintains the precision level required by the integral computations. PaSTRI is a part of ECP-EZ project, implemented as one of the compression algorithms in the SZ compressor. We have evaluated our compressor using GAMESS dataset, and achieved 17.5:1 compression ratio whereas compression ratios for original SZ was 8.0:1 and ZFP was 7.1:1.
Ali Murat Gok is a Ph.D. student(exp. 2018) from Northwestern University. He received his master degrees from Northwestern University(USA) and Bogazici University(Turkey).  His research interests are energy-efficient parallel architectures, approximate computing, power efficiency and reliability, hardware characterization, voltage over-scaling and compression algorithms. He is a summer intern in Argonne for three months, working with Franck Cappello, Sheng Di and Dingwen Tao in the data compression team under the ECP-EZ project.