quantum-espresso/TODO

TODO LIST - January 2010

1) Organization

1.1 www.quantum-espresso.org:
  1.1.1 update sample applications
  1.1.2 pseudopotential upload facility: done, to be checked
1.2 Wiki:
  1.2.1 move to qe-forge? is its current contents sensible?
1.3 CVS restructuring:
  1.3.1 no pseudopotentials in CVS any longer
  1.3.2 only general-purpose modules in Modules/
1.4 mailing lists:
  1.4.1 move to qe-forge
  1.4.2 better search facility. Use google with site:democritos.it ?
1.5 Interoperability:
  1.5.1 we should maintain somewhere (user guide? wiki? web page?)
        a list of external "QE-interoperable codes", that either
        provide input data for QE or read output/data files from QE

2) Documentation

2.1 "Manuale delle giovani marmotte". Start from my notes for the course
    of Electronic Structure, add more examples, with a short theoretical
    introduction followed by explanation of practical calculations, ending
    up with examples using QE. To begin with:
    - convergence tests with USPP
    - convergence tests with metals
    - cohesive energies
    - formation energies in defects (including charged defects)
    - variable-cell optimization
    - XPS spectra calculations
2.2 QE-Tutorial: should be moved to the cvs of qe-forge. 
    What are our plans for it, if any???
2.3 We should decide a strategy on where to put the documentation.
    Now it is in Doc/ for everything, except for atomic and GWW.
    We should decide which packages should have the documentation
    in other places. The same applies to examples.
2.4 Documentation on how to generate PP for GIPAW calculation is missing

3) Pseudopotentials 

3.1 Add Coulomb PPs - require first that we fix 1.1.2
3.2 Implement Goedecker PPs
3.3 Extend documentation in pseudo-gen.tex to the case of multiple
    projectors and to USPP (eventually to PAW)
3.4 Various proposals to extend the PP table with extensive/automated
    tests  (FM, NM, etc.)
3.5 Add default cutoff values as well as radii of augmented charge
    in pseudopotential files (they are present in recent PP only)

4) Development

4.1 Big new developments to add:
  4.1.0 ready: QHA (remove pwtools/fqha.f90)
  4.1.1 ready: TD-DFPT
  4.1.2 coming soon (?): vdW with nonlocal xc functional
  4.1.3 coming soon (?): new GWW
  4.1.4 coming soon (?): electron-phonon with Wannier stuff
  4.1.5 almost ready: interface with plumed for metadynamics
        once it works, old metadynamics stuff can be removed
  4.1.6 almost ready: G-space symmetrization. Once ready, the
        wrappers should be removed and the algorithm made final.
  4.1.7 next: bio-oriented stuff (Solvent Models, PCM, QM-MM)
  4.1.8 not big but ongoing (or not going) since a long time:
        Wyckoff interface
  4.1.9 not big but useful: collection of tools and utilities 
        for data analysis (things like g(r) from MD simulations)

4.2 Small new developments, desirable or to be added:
  4.2.1 configure issues:
        - ifort+acml
        - maybe we should use AC_PROG_FC instead of AC_PROG_F77
        - check if all MKL versions are recognized
        - add search for -lfftw3xf_intel 
        - remove obsolete stuff: mips alpha alinux macppc
  4.2.2 Add check if constraints break the symmetry
  4.2.3 inversion symmetry should allow real hamiltonian and wavefunctions
  4.2.4 nscf calculations are slow. There must be a way to make a better
        usage of the available information from the scf calculation:
        wavefunctions are just discarded. Same for phonon calculation: 
        it shouldn't be needed to recalculate everything almost from
        scratch at each different q-point
  4.2.5 Fermi-Dirac: pass T instead of "broadening", make it possible
        to use it on top of smearing for free-energy calculations
  4.2.6 add traceback in error (error_handler module)
  4.2.7 dynmat should write frequencies in a format that is suitable
        for direct plotting by gnuplot/xmgrace - see also Eyvaz' script
        for phonon plotting
  4.2.8 Move to a xml-based format for the dynamical matrix files
  4.2.9 Interface to RESP calculation - requires adding radii to xml file
  4.2.10 PH: C(R) should be calculated at the end of a dispersion run
  4.2.11 Gamma: same input as for PH
  4.2.12 stop with 'prefix.EXIT' and restart in D3 and Gamma (KK)
  4.2.13 PP, PH, etc., should read and use DFT written to xml file 
  4.2.14 Various defaults for CP (proposed from Princeton):
       - emass(emass=300), dt (dt=7), for preconditioning cutoff (3)
       - automatic box grid for USPP from radii of augmented charge
      - Electronic minimization: damp as default, sd discouraged
         introduce an automatic default schedule, something as:
         1st step sd followed by 5 steps with with damp= 0.8,
                     followed by 5 steps with damp=0.5,
                     followed by 10 steps with damp=0.3,
                     followed by 10 steps with damp=0.2,
                     followed by as many steps as necessary
                     to achieve the required convergence with damp=0.1
        A max number of steps should be included to ensure program termination.
        The other option allowed should be conjugate gradients:
       see NM - it could one day become the default
      -  Ionic minimization: again SD should be discouraged
         A default scheme for simultaneous damped dynamics should be given
         (to be tested) for example: zero damp on ions and start with damp=0.5
         on electrons to become then 0.1 or perhaps the values should be set
         given the forces on the ions
         When moving ions and electrons simultaneously an important parameter
         is the ratio between electron and ion masses - For minimization it 
         is better to set up all the ion masses equal - A default value for
         the ion masses (considering the defaults for emass and dt) is perhaps
         10 AMU (we should do some test to see if 20 AMU is s a safer value)
      - Default values for randomization should be given
        amprp=0.1 is a decent value - amprp=0.01 is too small
      - Car-Parrinello dynamics: the proper masses for the ions, an optimal
        value for emass and dt should be set up by the code, based on the 
        smaller atomic mass and the default value used in the minimization
        e.g. Amass_default=10 AMU. If the minimum physical AMASS is 20 then
        dt=sqrt(2) dt_default and emass should be increased so to keep
        emass^2/dt constant
      - defaults for the Nose thermostat

4.3 Performance enhancements/Parallelization:
  4.3.1 make hpsi/spsi/CG  faster
        - remove complex factor i**l from beta fct and q(r)
        - shift structure factor from beta to psi when computing becp 
          (reduce memory)
        - use real BLAS routine instead of COMPLEX one in hpsi/spsi 
          (at least 2 times faster).
        - use only half of the G's when computing real integrals
          (2 times faster)
        - seek for CG and DIIS algoritms that only use (H-eS)|psi>
          and not the two vector separately ... compute it in one single
          call. In this way S|psi> is inexpensive
  4.3.2 Try the new "Density-Matrix-Based" diagonalization algorithm
  4.3.3 grid-ization/parallelization of the phonon code: irreps and
        q-vectors should be distributed across processors/grid computers
  4.3.4 PH: use charge mixing instead of potential mixing
  4.3.5 D3: verify status of parallelization, clean it up if needed

4.4 Cleanup
  4.4.1 Increase modularization by 
        - collecting variables and routines acting on those variables
          into modules (e.g.: symmetry)
        - classifying modules in a hierarchical way
        - avoiding as much as possible that modules depend on many
          other modules
  4.4.2 Avoid monster routines that do too many things at the same time
        depending on the value of too many variables. An example:
        read_file
  4.4.3 There is some confusion in the various initialization steps:
         - default values at startup
         - reading of the input data and copy into internal variables
         - reading from data file
         - initialization of general variables (that presumably will
           be written to or read from file)
         - initialization of variables used in a specific calculation
          (that may not be written to or read from the data file)
        All these steps are intermixed and/or replicated and it is 
        never clear what is initialized where. Same for variable
        allocation: see recent GIPAW workaround for an example of
        allocation confusion (qnorm, cell_factor in allocate_nlpot)
  4.4.4 More PW/CP merge:
        - "cell_base_init" from CP to PW
        - "cellmd" module of PW and "cell_base" of CPV
        - PW "real-space" approach / CP "small boxes" 
        - there should be a single function or routine for periodic boundary 
          conditions (i.e. bringing all atoms inside the unit cell)
        - spherical harmonics and integration routines
        - merge of atomic positions! currently CP uses a complex logic
          that is very hard to follow
  4.4.5 Use qexml for xml file processing so that a single, easily
        exportable routine, is used everywhere. Requires some though
        on how to deal with parallelism without filling qexml with
        parallel stuff
  4.4.6 adding/removing/modifying input variables is too complex
        Why are some checks on input variables performed in read_namelist,
        while others apparently similar are in */input.f90?
  4.4.7 Units: all units should be clearly documented and reprinted 
        on output (and also exactly what the printed quantites are)
  4.4.8 There should be a function calculating dj_l/dx;
        j_l with l=-1 should not be needed
  4.4.9 too many confusing error messages are still around
  4.4.10 Output should be more informative and less confused, better
         structured, and ready for automatic reading by xcrysden
  4.4.11 any possibility to merge the various solve_* in PH ?
  4.4.12 Replace "use pwcom" with more "use" statements
  4.4.13 The calculation of P_c x|\psi> should be extracted from PH, 
         since it may be used for other calculations as well
         (TDDFT, photoemission cross sections, etc)
  4.4.14 All allocated variables should be deallocated at the end:
         it makes easier to find memory leaks. Currently most variables
         are deallocated, but a few (mostly in ffts and in pseudopotential
         reading) aren't

4.5 Trouble-makers. inconsistencies, etc
  4.5.1 Negative Charge problems (see qe-forge, H on graphene)
  4.5.2 Miller indices: a potential memory bottleneck, used only for GWW!!!
  4.5.3 G-vector shells, especially in the variable-cell case, and the 
        various tricks to reduce cpu by not re-calculating things that 
        depend on |G| only (see e.g. qvan2). Maybe we should move to 
        interpolation of all quantities and get rid of shells and tricks
  4.5.4 PP: complete postprocessing in Gamma case (only average missing),
        and with CP data (in the latter case: when the data file does
        not contain the charge/potential, issue an error message saying
        what is missing and why instead of just crashing in iotk)
  4.5.5 default 'atomic+random' for starting wavefunctions (NM),
        or else add a "hole finder" at the end of the scf run (SB)
        to prevent nasty unphysical results in some cases
  4.5.6 CP: add error check if dt^2/emass too large does not allow ortho
        to converge or cause energy to increase as time step evolve
  4.5.7 epsilon.x should be extended at least to have the nonlocal
        contribution included; there should be a pointer in the
        documentation explaining how to make a better calculation.
  4.5.8 There should be a check on the FFT grid preventing a bad 
        choice of Nr1,Nr2,Nr3 (e.g. different Nr for axis of the
        same length or even worse related by symmetry): this is a
        frequent source of trouble with electron-phonon calculations
  4.5.9 Still a few quirks with the atomic coordinate parser, if 
        DOS characters or tabulators are present (Lorenzo)
  4.5.10 Scratch files are a big mess. It should be possible
	 to open files in places other than tmp_dir without resorting 
	 to obscure coding. This is especially serious for PH, D3 etc
  4.5.11 Pseudopotential files are read in parallel by all processors.
         Maybe this is not a great idea