CYANA Command: minimize

Parameters

steps=integer

(default: 100)

level=integer

(default: 0)

flat=integer

(default: 100)

angdev=real

(default: 10.0)

vdwupdate=integer

(default: 100)

Description

Performs conjugate gradient minimization steps. Restraints up to the given minimization level are included in the target function. The conjugate gradient minimizer is stopped if within flat minimization steps the target function cannot be reduced by at least 1%. The van der Waals interaction list is updated every vdwupdate steps or each time a torsion angle has changed its value by more than angedev degrees since the last update of the van der Waals interaction list. If the information level is normal or higher, one line of information will be printed out as in the following example from the macro vtfmin:

 Minimization (standard strategy):
  lev    upper    lower        vdw   angle target funct. |grad| #up #f stop
         # act    # act     #  act   # act  begin    end    end
    0  115  13    0   0   313   26  84   9 282.65   0.13 1.8E-2   0 150 maxit
    1  271  47    0   0   925   73  84   5 163.09   3.79   0.16  34 150 maxit
    2  299  51    0   0  1067   81  84   5  24.71   3.79   0.11  18 150 maxit
    3  381  57    0   0  1240   92  84   8 694.27   4.22   0.27  20 116 flat
    4  431  74    0   0  1335   90  84  10  21.83   4.47   0.16   9 130 flat

The first column gives the minimization level. Then, there are four times two columns giving the total number of restraints and the number of "active" restraints for the upper limit restraints, the lower limit restraints, the intrinsic van der Waals lower limit restraints, and the angle restraints, respectively. “Active” restraints are those that yield non-vanishing (but often small) contributions to the target function. The next columns give the value of the target function at the beginning and at the end of the minimization step, the norm of the gradient of the target function at the end of the minimization step, the number of updates of the van der Waals contact list, the number of target function evaluations, and a stop code. The following stop codes may occur:

gradtl

The squared norm of the gradient of the target function is small.

maxit

The maximal number of target function evaluations, given by the parameter steps, has been exceeded.

linmin

The maximal number of target function evaluations during the one-dimensional line minimization has been exceeded without decreasing the target function value.

nostep

The step size during line minimization became too small.

uphill

The direction of a conjugate gradient minimization step was uphill.

const

Several conjugate gradient steps did not succeed in decreasing the target function.

flat

The target function was minimized by less than 1% during the preceding flat iterations.

stuck

Several attempts to restart the conjugate minimizer after an update of the steric interaction pair list failed.

Normal stop criteria are gradtl, maxit, and flat. Others should occur only rarely.

See also

• vtfmin