Using PALM to integrate variational data assimilation algorithms with OPA ECMWF, 29 june 2005, Reading. Nicolas Daget CERFACS, Toulouse
Mar 28, 2015
Using PALM to integrate variational data assimilation algorithms with OPA
ECMWF, 29 june 2005, Reading.
Nicolas DagetCERFACS, Toulouse
Dynamic coupling for parallel programs
Easy and user friendly to set up different assimilation systems
Independence of the components
High performance communications for data exchanges
Components can be launch dynamically
Complete independence between components and the algorithm
Distributed data exchange
Physics and algebraic computations are separated
PALM Philosophy
Algebraic computations can be done by PALM
PALM unit
Unit
Inputs
Outputs
Direct communication
Communication with a buffer
Priority
Inside a loop
Branch
Data assimilation algorithmsDirect model, tangent model
and adjoint model
Data assimilation
3DVAR Shallow Water
Model Read observations
Minimization
3DVAR with OPA
In situ temperature only
No background quality control
First prototype
3DVAR with OPA
Rea
d O
bser
vatio
nsC
ompu
te f
irst
Jo
Model
Compute first Jb and grad J
Minimizer
Com
pute Jo
Compute Jb and grad J
3DVAR with OPA
Read data
H
Initialization of R
1R
Reset variables
THFirst Jo
3DVAR with OPA
Read restart file, nit000, nitend, etc
Model initialization (opa.F without step.F)
Tangent model initialization
Model integration (step.F)
Mem
ory shared
Initialization of B
3DVAR with OPA
2BT
First grad J
First Jb
First Jo
Put inputs to minimizer
Control vector
2BT
Grad J
Jb2
1
B Put J and grad J
Minimizer : Lanczos algorithm linear equation and eigenvalue solver
Jo
3DVAR with OPA
Loop inside minimizer
Loop synchronized
with the minimizer
3DVAR with OPA
HTH
-1RJo
3DVAR with OPA
Direct Model
Read observation
H
H
HT
R-1
B1/2
BT/2
Minimizer
3DVAR
inner loop
outer loop
First version will come soon
In progress
Conclusions
• Hard work to split OPAVAR in units
• Direct, tangent and adjoint model can't be separated
• First 3DVar with OPA8.2 is not yet finished
• Easy to understand and modify algorithms
• Easiest to replace OPA8.2 by NEMO
• No information about optimization