ROMS/TOMS Developers

Algorithms Update Web Log

arango - August 16, 2006 @ 18:02
4DVAR Conjugate Gradient Step-Size- Comments (0)

The minimization in the descent algorithm for inner loop iteration n is given by

     last page eq1

where αn is the step size and dn are the conjugate direction vectors:

     last page eq2

     last page eq3


     last page eq4

The steepest descent occurs when β = 0. This happens either every NiterSD iterations or when dot2 > CGtol * dot1, where

     last page eq5

     last page eq6

The refined step size is computed in the second inner loop pass, m = 2, as

     last page eq7

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