[CP2K-user] Weird "convergence" of L-BFGS CELL_OPT

[Daniele Ongari]

Thanks you all for your replies, 
I will then consider that this is just a "fake" convergence and I will 
doublecheck always the SCF convergence in my parser. 

Daniele

Il giorno venerdì 22 febbraio 2019 14:39:15 UTC+1, Daniele Ongari ha 
scritto:
>
> Dear CP2K mailing list,
>
> We experience a strange behavior of the L-BFGS optimization algorithm when 
> dealing with cases where SCF convergence is problematic.
>
> After 20 minimization steps the cp2k printed the following:
>
>
> --------  Informations at step =    21 ------------
>  Optimization Method        =                LBFGS
>  Total Energy               =     -2345.6430825804
>  Internal Pressure [bar]    =        23.9760390703
>  Real energy change         =         0.0028283710
>  Decrease in energy         =                   NO
>  Used time                  =             5864.105
>
>  Convergence check :
>  Max. step size             =         0.0000000000
>  Conv. limit for step size  =         0.0030000000
>  Convergence in step size   =                  YES
>  RMS step size              =         0.0000000000
>  Conv. limit for RMS step   =         0.0015000000
>  Convergence in RMS step    =                  YES
>  Max. gradient              =         0.0082916384
>  Conv. limit for gradients  =         0.0004500000
>  Conv. for gradients        =                   NO
>  RMS gradient               =         0.0009846623
>  Conv. limit for RMS grad.  =         0.0003000000
>  Conv. for gradients        =                   NO
>  Pressure Deviation [bar]   =       -76.0239609297
>  Pressure Tolerance [bar]   =       100.0000000000
>  Conv. for  PRESSURE        =                  YES
> ---------------------------------------------------
>
> --------------------------
> OPTIMIZATION STEP:     22
> --------------------------
>
> ***********************************************
> * Specific L-BFGS convergence criteria
> * WANTED_PROJ_GRADIENT and WANTED_REL_F_ERROR
> * satisfied .... run CONVERGED!
> ***********************************************
>
>
>
> The two things that look strange for us are:
>
> 1) Max. step size and RMS step size were 'artificially' set to 0.0000000000
> 2) Not all checks are showing convergence, while L-BFGS algorithm has 
> decided to stop.
>
>
> Therefore, we would like to know if this is an expected behavior of the 
> L-BFGS algorithm and if yes, what is the reason behind working this way?
>
> Please see input and output files attached.
>
> With best regards,
> Daniele and Sasha
>
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