Merge pull request #133 from muralidhar-nalabothula/master

Change default ELPA solver when running on GPUs
yambo-code · Sep 9, 2024 · 58e3770 · 58e3770
2 parents 3ac7e23 + cef1182
commit 58e3770
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Showing 2 changed files with 17 additions and 5 deletions.
diff --git a/src/bse/K_diago_driver.F b/src/bse/K_diago_driver.F
@@ -252,8 +252,8 @@ subroutine K_diago_driver(iq,W,X_static)
        ! SL and diagonalize entire hamilitonian
        ! NM : BS_V_left are only referenced in non-hermitian case
        ! Note that in coupling case, if the user requested n values,
-       ! This means that the we compute the first n posive and n 
-       ! negative, making it a total of 2n.
+       ! This means that the we compute the first min(n,BS_H_dim/2) positive and 
+       ! min(n,BS_ham/2) negative eigvals and eigvectors, making it a total of 2*min(n,BS_ham/2)
        !
        if (.not. l_eval_range) then
          ! Use index range

diff --git a/src/bse/K_diagonalize.F b/src/bse/K_diagonalize.F
@@ -64,11 +64,11 @@ subroutine K_diagonalize(i_BS_mat, BS_energies, BS_VR, &
   !
   ! Local variables
   type(c_ptr)                        :: mpicxt, diago_mat, evecs
-  integer                            :: nProcs, my_rank, blacs_blk_size
+  integer                            :: nProcs, my_rank
   integer(YDIAGO_INT)                :: SL_H_dim, ProcX, ProcY, elpa_nthreads
   integer(ERROR_INT)                 :: error_diago ! diagonalization error code
-  integer                            :: ierr, i_c, i_r !! mpi error code 
-  integer(YDIAGO_INT)                :: neig_found
+  integer                            :: ierr !! mpi error code 
+  integer(YDIAGO_INT)                :: neig_found, i_c, i_r, blacs_blk_size 
   integer(YDIAGO_LL_INT)             :: nelements
   ! optional local vars with their defaults
   character                          :: solver_type_aux   = 's'
@@ -103,6 +103,14 @@ subroutine K_diagonalize(i_BS_mat, BS_energies, BS_VR, &
   call set_elpa_gpu_str(gpu_device_elpa)
   if (gpu_device_elpa(1:3) /= c_char_"not") then 
     gpu_str = c_loc(gpu_device_elpa)
+    ! NM: ELPA GPU for now does not support solver type =2, 
+    ! in this case we force the solver to be type=1 (i.e standard QR)
+    ! In future, if it works, we need to remove this.
+    ! See https://github.com/marekandreas/elpa/blob/master/src/elpa2/elpa2_template.F90#L1742
+    if (elpa_solver_aux .eq. 2) then 
+      call msg("s", 'Warning : ELPA Solver 2 is not GPU Ported. Switching to QR Solver.') 
+      elpa_solver_aux = 1
+    endif
   else 
     call msg("s", 'Warning : Ydiago not compiled with GPU. using CPU version')
     gpu_str = c_null_ptr
@@ -187,6 +195,7 @@ subroutine K_diagonalize(i_BS_mat, BS_energies, BS_VR, &
     !
   endif
   !
+#if defined _ELPA
   if (solver_type_aux .eq. 'e') then
     !
     call section('=','ELPA Diagonalization')
@@ -196,6 +205,9 @@ subroutine K_diagonalize(i_BS_mat, BS_energies, BS_VR, &
     call section('=','Scalapack Diagonalization')
     !
   endif
+#else 
+  call section('=','Scalapack Diagonalization')
+#endif
   !
   ! Call the solvers
   !