Benchmarking: Stream (Memory Bandwidth)

STREAM: The STREAM benchmark is a simple synthetic benchmark program that measures sustainable memory bandwidth (in MB/s) and the corresponding computation rate for simple vector kernels.

• Note: Ensure power saving features are disabled, we need max clock speed to prevent fluctuations in performance:
  • /etc/init.d/cpuspeed stop

Get the source

• Main STREAM website: http://www.cs.virginia.edu/stream/
• Pull the latest copy of STREAM from:

  # (v 5.10 at the time of edit)
  wget http://www.cs.virginia.edu/stream/FTP/Code/stream.c

Compile

• Can use either Intel or GCC to build/compile
• Ensure you build for multi-threaded runs (-fopenmp (gcc) -openmp (icc)
• For large array sizes, include -mcmodel=medium
• Noticed best performance using Intel ICC

Intel

GCC

Open 64

• Best to optimising on AMD arch

/shared/apps/open64-5.0/bin/opencc -march=bdver1 -mp -Ofast -LNO:simd=2 -WOPT:sib=on  \
     -LNO:prefetch=2:pf2=0 -CG:use_prefetchnta=on -LNO:prefetch_ahead=4 -DSTREAM_ARRAY_SIZE=30000000 \
     -DNTIMES=30 -DOFFSET=1840 stream.c -o stream_occ

Run

• Vary the number of threads used by using: export OMP_NUM_THREADS=32

Results