Configuring Parameters

The most significant parameters in HPL.dat are P, Q, NB, and N. Specify them as follows:

• P and Q - the number of rows and columns in the process grid, respectively.

  P*Q must be the number of MPI processes that HPL is using.

  Choose P≤Q.

• NB - the block size of the data distribution.

  The table below shows recommended values of NB for different Intel® processors:

  Processor	NB
  Intel® Xeon® Processor X56*/E56*/E7-*/E7*/X7* (codenamed Nehalem or Westmere)	256
  Intel Xeon Processor E26*/E26* v2 (codenamed Sandy Bridge or Ivy Bridge)	256
  Intel Xeon Processor E26* v3/E26* v4 (codenamed Haswell or Broadwell)	192
  Intel® Core™ i3/i5/i7-6* Processor (codenamed Skylake Client)	192
  Intel® Xeon Phi™ Processor 72* (codenamed Knights Landing)	336
  Intel Xeon Processor supporting Intel® Advanced Vector Extensions 512 (Intel® AVX-512) instructions (codenamed Skylake Server)	384

• N - the problem size:

  • For homogeneous runs, choose N divisible by NB*LCM(P,Q), where LCM is the least common multiple of the two numbers.

  • For heterogeneous runs, see Heterogeneous Support in the Intel® Distribution for LINPACK* Benchmark for how to choose N.

  Note

  Increasing N usually increases performance, but the size of N is bounded by memory. In general, you can compute the memory required to store the matrix (which does not count internal buffers) as 8*N*N/(P*Q) bytes, where N is the problem size and P and Q are the process grids in HPL.dat. A general rule of thumb is to choose a problem size that fills 80% of memory.