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HPCG Performance study with Intel Skylake processors

Author: Somanath Moharana and Ashish Kumar Singh, Dell EMC HPC Innovation Lab,

September 2017

This blog presents analysis of the High Performance Conjugate Gradient (HPCG) benchmark on

the Intel(R) Xeon(R) Gold 6150 CPU codename “Skylake”. It also compares the performance of

Intel(R) Xeon(R) Gold 6150 processors with its previous generation Intel(R) Xeon(R) CPU E5-

2697 v4 Codename “Broadwell-EP” processors.

Introduction to HPCG

The High Performance Conjugate Gradients (HPCG) Benchmark is a metric for ranking HPC

systems. HPCG can be considered as a complement to the High Performance LINPACK (HPL)

benchmark. HPCG is designed to exercise computational and data access patterns that more

closely match a different and broad set of applications that have impact on the collective

performance of these applications.

The HPCG benchmark is based on a 3D regular 27-point discretization of an elliptic partial

differential equation. The 3D domain is scaled to fill a 3D virtual process grid for all of the

available MPI ranks. The preconditioned conjugate gradient (CG) algorithm is used to solve the

intermediate systems of equations and incorporates a local and symmetric Gauss-Seidel pre-

conditioning step that requires a triangular forward solve and a backward solve. The benchmark

exhibits irregular accesses to memory and fine-grain recursive computations.

HPCG has four computational blocks: Sparse Matrix-vector multiplication (SPMV), Symmetric

Gauss-Seidel (SymGS), vector update phase (WAXPBY) and Dot Product (DDOT), while two

communication blocks MPI_Allreduce and Halos Exchange.

Introduction to Intel Skylake processor

Intel Skylake is a microarchitecture redesign using the same 14 nm manufacturing process

technology with support for up to 28 cores per socket, serving as a "tock" in Intel's "tick-tock"

manufacturing and design model. It supports 6 DDR4 memory channels per socket with 2 DPC

(DIMMs per channel), where supported full memory bandwidth is up to 2666 MT/s.

Please visit BIOS characteristics of Skylake processor-blog for a better understanding of Skylake

processors and their bios features on Dell EMC platforms.

Summary of content (4 pages)

PAGE 1
HPCG Performance study with Intel Skylake processors Author: Somanath Moharana and Ashish Kumar Singh, Dell EMC HPC Innovation Lab, September 2017 This blog presents analysis of the High Performance Conjugate Gradient (HPCG) benchmark on the Intel(R) Xeon(R) Gold 6150 CPU codename “Skylake”. It also compares the performance of Intel(R) Xeon(R) Gold 6150 processors with its previous generation Intel(R) Xeon(R) CPU E52697 v4 Codename “Broadwell-EP” processors.
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Table 1: Details of Servers used for HPCG analysis Platforms PowerEdge C6420 PowerEdge R630 Processor 2 x Intel(R) Xeon(R) Gold 6150 @2.7GHz, 18c 192GB (12 x 16GB) DDR4 2 x Intel(R) Xeon(R) CPU E5-2697 v4 @2.3GHz, 18c 128GB(8 x 16GB ) DDR4 @2666MT Intel Omni Path @2400MT Intel Omni path Compiler Red Hat Enterprise Linux Server release 7.3 version 2017.0.4.196 Red Hat Enterprise Linux Server release 7.2 version 2017.0.098 MKL Intel® MKL 2017.0.3 Intel® MKL 2017.0.
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Figure 1: HPCG Performance on multiple grid sizes with Intel Xeon Gold 6150 processors As shown in figure 1, we can observe that the local dimension grid size of 192^3 gives the best performance compared to other local dimension grid sizes i.e. 160^3 and 224^3. Here we are getting a performance of 36.14 GFLOP/s for a single node and we can observe a linear increase in performance with the increase in number of nodes.
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Figure 3: HPCG performance over multiple generation of Intel processors Figure 3 compares HPCG performance between Intel Broadwell-EP processors and Intel Skylake processors. Dots in the figure shows the performance improvement of Intel Skylake over Broadwell-EP processors. For a single node, we can observe ~65% better performance with Skylake processor than Broadwell-EP processors and ~67% better performance for both two nodes and four nodes.