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<div>Dear developers,</div><div> I tried to use -ndiag options in scf process. Because I read tutorials which says "most CPU time spent in linear-algebra operations, implemented in BLAS and LAPACK libraries, and in FFT". And what linear algebra parallelization does is to "Distribute and parallelize matrix diagonalization and matrix- matrix multiplications needed in iterative diagonalization (SCF) ". So I thought adding -ndiag should have an obvious speedup. To test, I artificially construct a 2x2 supercell of copper which contains 8 atoms, and run</div><div><br></div><div>mpiexec.hydra -n 12 pw.x -ndiag 9 -in cu_supercell.scf.in > <span style="line-height: 23.8px;">cu_supercell.scf.out</span></div><div><span style="line-height: 23.8px;"><br></span></div><div><span style="line-height: 23.8px;">But I didn't see any improvement over no -ndiag run. The timing is almost the same. I check the output file, it does show that</span></div><div><span style="line-height: 23.8px;"><br></span></div><div>Subspace diagonalization in iterative solution of the eigenvalue problem:</div><div> one sub-group per band group will be used</div><div> scalapack distributed-memory algorithm (size of sub-group: 3* 3 procs)</div><div><span style="line-height: 23.8px;"><br></span></div><div><span style="line-height: 23.8px;">I also test a more practical case with a material of 23 atoms in primitive cell, and see no improvement. So I am wondering what is wrong? Is -ndiag not effective for scf? </span></div><div><span style="line-height: 23.8px;"><br></span></div><div><span style="line-height: 23.8px;"><br></span></div><div><span style="line-height: 23.8px;">best regards</span></div><div><span style="line-height: 23.8px;"><br></span></div><div><span style="line-height: 23.8px;"><br></span></div><div> </div><div id="ntes-pcmail-signature" style="font-family:'微软雅黑'"><font style="padding: 0; margin:0;"> </font>
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