Using plans

PEXSI is written in C++, and the subroutines cannot directly interface with other programming languages such as C or FORTRAN. To solve this problem, the PEXSI internal data structure is handled using a datatype PPEXSIPlan. The idea and the usage of PPEXSIPlan is similar to fftw_plan in the FFTW package.

In PEXSI, a matrix is generally referred to as a "pole". The factorization and selected inversion procedure for a pole is computed in parallel using numProcRow * numProcCol processors.

When only selected inversion (PSelInv) is used, it is recommended to set the mpisize of the communicator comm to be just numProcRow * numProcCol.

When PEXSI is used to evaluate a large number of inverse matrices such as in the electronic structure calculation, mpisize should be numPole*numProcRow*numProcCol, where numPole inverse matrices can be processed in parallel.

#include  "c_pexsi_interface.h"
...
{
  PPEXSIPlan   plan;

  plan = PPEXSIPlanInitialize( 
      comm, 
      numProcRow,
      numProcCol,
      outputFileIndex, 
      &info );

  /* ... Computation using plan ... */

  PPEXSIPlanFinalize(
      plan,
      &info );
}