BFGS: the initial step is reduced when the forces are smaller than a given threshold.

The linear scaling algorithm has been removed (never used and bad performance) allowing for
a considerable clean up of the module.
A new Pulay mixing has been added on top of the BFGS scheme which improves (sometimes considerably)
the performace of the relaxation (similar to the GDIIS). It is activated by setting bfgs_ndim (default is 1
which corresponds to no Pulay mixing). The algorithm has to be tested against difficoult problems.
C.S.


git-svn-id: http://qeforge.qe-forge.org/svn/q-e/trunk/espresso@1823 c92efa57-630b-4861-b058-cf58834340f0

Doc/INPUT_PW

@@ -578,13 +578,12 @@ upscale        REAL ( default = 10.D0 )
                but conv_thr will not be reduced to less that 
                conv_thr / upscale
 
-lbfgs_ndim     INTEGER ( default = 1 )
+bfgs_ndim      INTEGER ( default = 1 )
                number of old forces and displacements vectors used in the
-	       linear scaling BFGS algorithm. When lbfgs_ndim = 1 the complete
-	       inverse Hessian is stored (suggested for small/medium-size 
-	       systems).
-	       On large systems (some hundreds of atoms) a good performance can 
-	       be achieved with only 4 or 6 old vectors 
+	       PULAY mixing of the residual vectors obtained on the basis
+               of the inverse hessian matrix given by the BFGS algorithm.
+               When bfgs_ndim = 1, the standard quasi-Newton BFGS method is
+               used.
                (bfgs only)
 
 trust_radius_max

Modules/input_parameters.f90

@@ -1030,7 +1030,7 @@ MODULE input_parameters
         ! ... variables added for new BFGS algorithm
         !
         
-        INTEGER ::  lbfgs_ndim = 1
+        INTEGER ::  bfgs_ndim = 1
                             
         REAL(KIND=DP)  :: trust_radius_max = 0.5D0
         REAL(KIND=DP)  :: trust_radius_min = 1.D-5
@@ -1106,7 +1106,7 @@ MODULE input_parameters
                           fixed_tan, use_freezing, use_fourier,           &
                           trust_radius_max, trust_radius_min,             &
                           trust_radius_ini, trust_radius_end, w_1, w_2,   &
-                          lbfgs_ndim, sic_rloc,                           &
+                          bfgs_ndim, sic_rloc,                            &
                           smd_polm, smd_kwnp, smd_linr, smd_stcd,         &
                           smd_stcd1, smd_stcd2, smd_stcd3, smd_codf,      &
                           smd_forf, smd_smwf, smd_lmfreq, smd_tol,        &

Modules/read_namelists.f90

@@ -380,7 +380,7 @@ MODULE read_namelists_module
        !
        ! ... BFGS defaults
        !
-       lbfgs_ndim       = 1
+       bfgs_ndim        = 1
        trust_radius_max = 0.8D0
        trust_radius_min = 1.D-5
        trust_radius_ini = 0.5D0
@@ -781,7 +781,7 @@ MODULE read_namelists_module
        !
        ! ... BFGS
        !
-       CALL mp_bcast( lbfgs_ndim, ionode_id )
+       CALL mp_bcast( bfgs_ndim, ionode_id )
        CALL mp_bcast( trust_radius_max, ionode_id )
        CALL mp_bcast( trust_radius_min, ionode_id )
        CALL mp_bcast( trust_radius_ini, ionode_id )

PW/input.f90

@@ -163,7 +163,7 @@ SUBROUTINE iosys()
   !
   USE constraints_module, ONLY : nconstr, constr_tol, constr, target
   !
-  USE bfgs_module,   ONLY : lbfgs_ndim_       => lbfgs_ndim, &
+  USE bfgs_module,   ONLY : bfgs_ndim_        => bfgs_ndim, &
                             trust_radius_max_ => trust_radius_max, &
                             trust_radius_min_ => trust_radius_min, &
                             trust_radius_ini_ => trust_radius_ini, &
@@ -218,7 +218,7 @@ SUBROUTINE iosys()
                                ds, use_fourier, use_freezing, fixed_tan,       &
                                free_energy, write_save, trust_radius_max,      &
                                trust_radius_min, trust_radius_ini,             &
-                               trust_radius_end, w_1, w_2, lbfgs_ndim
+                               trust_radius_end, w_1, w_2, bfgs_ndim
   !
   ! CELL namelist
   !
@@ -1001,9 +1001,9 @@ SUBROUTINE iosys()
   fixed_tan_          = fixed_tan
   free_energy_        = free_energy
   !
-  ! ... new BFGS specific
+  ! ... BFGS specific
   !
-  lbfgs_ndim_       = lbfgs_ndim
+  bfgs_ndim_        = bfgs_ndim
   trust_radius_max_ = trust_radius_max
   trust_radius_min_ = trust_radius_min
   trust_radius_ini_ = trust_radius_ini

PW/move_ions.f90

@@ -41,7 +41,6 @@ SUBROUTINE move_ions()
   USE symme,         ONLY : s, ftau, nsym, irt
   USE ener,          ONLY : etot
   USE force_mod,     ONLY : force
-  USE bfgs_module,   ONLY : lbfgs_ndim
   USE control_flags, ONLY : upscale, lbfgs, loldbfgs, lconstrain, &
                             lmd, conv_ions, history, alpha0, beta0, tr2, istep
   USE relax,         ONLY : epse, epsf, starting_scf_threshold
@@ -52,7 +51,7 @@ SUBROUTINE move_ions()
   !
   ! ... external procedures
   !
-  USE bfgs_module,            ONLY : new_bfgs => bfgs, lin_bfgs, terminate_bfgs
+  USE bfgs_module,            ONLY : new_bfgs => bfgs, terminate_bfgs
   USE constraints_module,     ONLY : dist_constrain, check_constrain, &
                                      new_force
   USE basic_algebra_routines, ONLY : norm
@@ -129,23 +128,8 @@ SUBROUTINE move_ions()
         pos      =   RESHAPE( SOURCE = tau,   SHAPE = (/ 3 * nat /) ) * alat
         gradient = - RESHAPE( SOURCE = force, SHAPE = (/ 3 * nat /) )
         !
-        IF ( lbfgs_ndim == 1 ) THEN
-           !
-           ! ... standard BFGS 
-           !
-           CALL new_bfgs( pos, etot, gradient, tmp_dir, stdout, epse,        &
-                          epsf, energy_error, gradient_error, step_accepted, &
-                          conv_ions )
-           !
-        ELSE
-           !
-           ! ... linear scaling BFGS
-           !
-           CALL lin_bfgs( pos, etot, gradient, tmp_dir, stdout, epse,        &
-                          epsf, energy_error, gradient_error, step_accepted, &
-                          conv_ions )
-           !
-        END IF
+        CALL new_bfgs( pos, etot, gradient, tmp_dir, stdout, epse, epsf, &
+                       energy_error, gradient_error, step_accepted, conv_ions )
         !
         IF ( conv_ions ) THEN
            !