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Thursday, March 5 • 10:45 - 11:05
Reservoir/Production: 'Vectorization of Equation of State Calculations in Compositional Reservoir Simulation,” Shaji Chempath, Kjetil Haugen and Bret Beckner, ExxonMobil

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Reservoir simulations are computationally intensive and the next generation simulators will be using all available modern high performance computing tools for achieving maximum performance. ExxonMobil’s next generation simulator is designed to run in parallel on a large number of processors. Vectorization provides another way to further improve speedups by accelerating the calculations within a single cpu-core. A significant fraction of compositional reservoir simulations is spent on equation of state (EoS) calculations within each cell. We will present results of applying vectorization of EoS calculations within ExxonMobil’s next generation massively parallel reservoir simulator.

Vectorization in the traditional sense deals with an SIMD model were the SSE/AVX registers are used for parallelizing simple operations such as additions, and multiplications within a loop. We will present a different way of vectorizing an entire algorithm - Equation of State calculation - on SSE and AVX registers, with resulting speedup of 4-8 on a single CPU core. Ideal speed-ups are 4x on 128-bit SSE registers for 32-bit floating point operations (8x for the 256-bit AVX registers for 32-bit floating point operations). Rather than relying on individual loops being vectorized, we run the entire EoS calculation using vectorized variables, allowing 4 or 8 EoS calculations to be done simultaneously. To realize ideal speedups, we exploit the fact that, while there may be different branches within the EoS algorithm, the branching is very similar for spatially contiguous points in a reservoir simulation. For example, 8 adjacent cells in a reservoir simulation will have similar phase behavior and similar number of iterations during a phase-split calculation. EoS calculations within a compositional reservoir simulation have been scaled up by a factor of 4x-8x using this approach.


Thursday March 5, 2015 10:45 - 11:05 CST
BioScience Research Collaborative 6500 Main Street, Houston, Tx 77005

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