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["Scott P. Beckman" <sbeckman@ices.utexas.edu>]

Hello,

I'm trying to parallize over bands, but the SCF loop seems to not 
converge, or it blows up (if I pick nbdblock to be large).

I've read the archives and I've looked at the Test_v3/t41.in example 
file.  The only advice regarding the stability is to keep nbdblock 
small.  Even when I set nbdblock 1 which is unparalized (right?) the 
convergence is a problem.

Are there other parameters that I can change to improve convergence?  
Do I need to tweak the parameters of the CG minimization?  In the 
example Test_v3/t41.in the SCF loop is run using the default (CG 
minimization), is it better to switch to Anderson mixing (iscf=3)?

When I run the cell for nbdblock of 1, 2, and 4 it does seem to 
parallize because for a given wall-clock-time 4 times as many loops are 
calculated for nbdblock=4 than for nbdblock=1, but the ETOT ceases to 
reduce after the first 3 or 4 iterations.

Below I've attached the details of my calculation as well as a summary 
of the SCF loop run for nbdblock=2

I'd appreciate any advice.

Thank you,
Scott

=============

In my calculation I have 1 kpoint at gamma, no spin, and 448 states.

I'm running abinit 4.5.3 on the NERSC SP2 computer called, "seaborg"

Here is my input file (truncated):

#Definition of the unit cell
acell 3*30.78
rprim  0.0  0.0  1.0
           1.0  0.0  0.0
            0.0  1.0  0.0

#Definition of the atom types
ntypat 1          # There is only one type of atom
znucl 14         # It is Silicon

#number of states
nband 448

#parallelization parameters
localrdwf 0
wfoptalg 1
nbdblock 2
#mffmem 0
#mkmem 0

#Definition of the atoms
natom 216                 # There are eight atoms
typat 216*1
# They all of type 1, that is, Silicon.

xcart
      .000000      .000000      .000000
      .000000      .000000    10.254159
#  <214 other atoms which I've cut from this message...>

#Definition of the planewave basis set
ecut  16.0 Ry        # Maximal kinetic energy cut-off, in Hartree

#Definition of the k-point grid
kptopt 0          # Pick one point at Gamma

#Definition of the SCF procedure
nstep 100             # Maximal number of SCF cycles
toldfe 2.0d-4 Ry  # SCF tolerance

diemac 12.0        #For Silicon

==========

Here are the results from when I try using ndblock 2

-bash-2.05b$ grep 'ETOT' s*.out
s00509.0.out: ETOT  1  -751.47821637601    -7.515E+02 9.686E-03 
4.012E+02 7.504E-03 7.504E-03
s00509.0.out: ETOT  2  -747.33285059714     4.145E+00 3.070E-03 
7.908E+02 1.048E-02 7.148E-03
s00509.0.out: ETOT  3  -958.38383973537    -2.111E+02 5.495E-02 
1.511E+02 6.166E-03 1.878E-03
s00509.0.out: ETOT  4  -956.70213692513     1.682E+00 3.084E-02 
8.664E+02 3.306E-03 3.396E-03
s00509.0.out: ETOT  5  -956.62261883621     7.952E-02 2.473E-02 
4.942E+02 4.401E-03 3.986E-03
s00509.0.out: ETOT  6  -955.91889202857     7.037E-01 4.237E-02 
2.621E+02 6.614E-03 8.539E-03
s00509.0.out: ETOT  7  -957.68210559965    -1.763E+00 7.069E-02 
2.466E+02 7.053E-03 4.627E-03
s00509.0.out: ETOT  8  -956.68684912222     9.953E-01 1.178E-01 
6.697E+02 6.181E-03 6.405E-03
s00509.0.out: ETOT  9  -956.60608351456     8.077E-02 2.344E-02 
1.446E+02 5.416E-03 4.662E-03
s00509.0.out: ETOT 10  -957.08065326697    -4.746E-01 2.926E-01 
2.483E+01 5.151E-03 3.356E-03
s00509.0.out: ETOT 11  -956.36743550574     7.132E-01 2.268E-02 
1.044E+02 3.775E-03 4.755E-03
s00509.0.out: ETOT 12  -957.56864369269    -1.201E+00 5.286E-02 
4.373E+01 5.937E-03 4.396E-03
s00509.0.out: ETOT 13  -956.09735922438     1.471E+00 1.271E-02 
3.193E+01 5.647E-03 4.728E-03
s00509.0.out: ETOT 14  -956.37022803816    -2.729E-01 2.906E-02 
3.309E+01 5.269E-03 4.129E-03
s00509.0.out: ETOT 15  -956.67570978833    -3.055E-01 2.764E-02 
3.440E+01 5.590E-03 5.024E-03
s00509.0.out: ETOT 16  -956.48829691245     1.874E-01 2.715E-02 
5.744E+01 1.232E-02 7.456E-03
s00509.0.out: ETOT 17  -957.00396225354    -5.157E-01 7.132E-02 
2.999E+01 5.378E-03 4.806E-03
s00509.0.out: ETOT 18  -956.76329776060     2.407E-01 2.874E-02 
2.421E+01 6.049E-03 5.195E-03
s00509.0.out: ETOT 19  -955.60989295271     1.153E+00 2.172E-02 
6.916E+01 4.324E-03 5.136E-03
s00509.0.out: ETOT 20  -841.59537695346     1.140E+02 1.282E-01 
4.586E+04 1.667E-01 1.616E-01
s00509.0.out: ETOT 21  -949.31863557768    -1.077E+02 1.369E-01 
4.715E+02 1.672E-01 1.295E-02
s00509.0.out: ETOT 22  -957.41192412422    -8.093E+00 1.197E-02 
5.254E+01 1.418E-02 4.192E-03
s00509.0.out: ETOT 23  -838.38884562380     1.190E+02 2.301E-01 
2.640E+04 6.352E-02 6.183E-02
s00509.0.out: ETOT 24  -944.16123848793    -1.058E+02 3.139E-01 
3.868E+02 5.708E-02 1.139E-02
s00509.0.out: ETOT 25  -955.55830652936    -1.140E+01 1.534E-02 
1.131E+01 1.333E-02 4.026E-03