2 Copyright (C) 2008-2015 EDF R&D
4 This file is part of SALOME ADAO module.
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18 Foundation, Inc., 59 Temple Place, Suite 330, Boston, MA 02111-1307 USA
20 See http://www.salome-platform.org/ or email : webmaster.salome@opencascade.com
22 Author: Jean-Philippe Argaud, jean-philippe.argaud@edf.fr, EDF R&D
24 .. index:: single: 3DVAR
25 .. _section_ref_algorithm_3DVAR:
27 Calculation algorithm "*3DVAR*"
28 -------------------------------
33 This algorithm performs a state estimation by variational minimization of the
34 classical :math:`J` function in static data assimilation:
36 .. math:: J(\mathbf{x})=(\mathbf{x}-\mathbf{x}^b)^T.\mathbf{B}^{-1}.(\mathbf{x}-\mathbf{x}^b)+(\mathbf{y}^o-\mathbf{H}.\mathbf{x})^T.\mathbf{R}^{-1}.(\mathbf{y}^o-\mathbf{H}.\mathbf{x})
38 which is usually designed as the "*3D-VAR*" function (see for example
41 Optional and required commands
42 ++++++++++++++++++++++++++++++
44 .. index:: single: AlgorithmParameters
45 .. index:: single: Background
46 .. index:: single: BackgroundError
47 .. index:: single: Observation
48 .. index:: single: ObservationError
49 .. index:: single: ObservationOperator
50 .. index:: single: Minimizer
51 .. index:: single: Bounds
52 .. index:: single: MaximumNumberOfSteps
53 .. index:: single: CostDecrementTolerance
54 .. index:: single: ProjectedGradientTolerance
55 .. index:: single: GradientNormTolerance
56 .. index:: single: StoreSupplementaryCalculations
57 .. index:: single: Quantiles
58 .. index:: single: SetSeed
59 .. index:: single: NumberOfSamplesForQuantiles
60 .. index:: single: SimulationForQuantiles
62 The general required commands, available in the editing user interface, are the
66 *Required command*. This indicates the background or initial vector used,
67 previously noted as :math:`\mathbf{x}^b`. Its value is defined as a
68 "*Vector*" or a *VectorSerie*" type object.
71 *Required command*. This indicates the background error covariance matrix,
72 previously noted as :math:`\mathbf{B}`. Its value is defined as a "*Matrix*"
73 type object, a "*ScalarSparseMatrix*" type object, or a
74 "*DiagonalSparseMatrix*" type object.
77 *Required command*. This indicates the observation vector used for data
78 assimilation or optimization, previously noted as :math:`\mathbf{y}^o`. It
79 is defined as a "*Vector*" or a *VectorSerie* type object.
82 *Required command*. This indicates the observation error covariance matrix,
83 previously noted as :math:`\mathbf{R}`. It is defined as a "*Matrix*" type
84 object, a "*ScalarSparseMatrix*" type object, or a "*DiagonalSparseMatrix*"
88 *Required command*. This indicates the observation operator, previously
89 noted :math:`H`, which transforms the input parameters :math:`\mathbf{x}` to
90 results :math:`\mathbf{y}` to be compared to observations
91 :math:`\mathbf{y}^o`. Its value is defined as a "*Function*" type object or
92 a "*Matrix*" type one. In the case of "*Function*" type, different
93 functional forms can be used, as described in the section
94 :ref:`section_ref_operator_requirements`. If there is some control :math:`U`
95 included in the observation, the operator has to be applied to a pair
98 The general optional commands, available in the editing user interface, are
99 indicated in :ref:`section_ref_assimilation_keywords`. Moreover, the parameters
100 of the command "*AlgorithmParameters*" allows to choose the specific options,
101 described hereafter, of the algorithm. See
102 :ref:`section_ref_options_Algorithm_Parameters` for the good use of this
105 The options of the algorithm are the following:
108 This key allows to choose the optimization minimizer. The default choice is
109 "LBFGSB", and the possible ones are "LBFGSB" (nonlinear constrained
110 minimizer, see [Byrd95]_, [Morales11]_ and [Zhu97]_), "TNC" (nonlinear
111 constrained minimizer), "CG" (nonlinear unconstrained minimizer), "BFGS"
112 (nonlinear unconstrained minimizer), "NCG" (Newton CG minimizer). It is
113 strongly recommended to stay with the default.
115 Example : ``{"Minimizer":"LBFGSB"}``
118 This key allows to define upper and lower bounds for every state variable
119 being optimized. Bounds have to be given by a list of list of pairs of
120 lower/upper bounds for each variable, with possibly ``None`` every time
121 there is no bound. The bounds can always be specified, but they are taken
122 into account only by the constrained optimizers.
124 Example : ``{"Bounds":[[2.,5.],[1.e-2,10.],[-30.,None],[None,None]]}``
127 This key indicates the maximum number of iterations allowed for iterative
128 optimization. The default is 15000, which is very similar to no limit on
129 iterations. It is then recommended to adapt this parameter to the needs on
130 real problems. For some optimizers, the effective stopping step can be
131 slightly different of the limit due to algorithm internal control
134 Example : ``{"MaximumNumberOfSteps":100}``
136 CostDecrementTolerance
137 This key indicates a limit value, leading to stop successfully the
138 iterative optimization process when the cost function decreases less than
139 this tolerance at the last step. The default is 1.e-7, and it is
140 recommended to adapt it to the needs on real problems.
142 Example : ``{"CostDecrementTolerance":1.e-7}``
144 ProjectedGradientTolerance
145 This key indicates a limit value, leading to stop successfully the iterative
146 optimization process when all the components of the projected gradient are
147 under this limit. It is only used for constrained optimizers. The default is
148 -1, that is the internal default of each minimizer (generally 1.e-5), and it
149 is not recommended to change it.
151 Example : ``{"ProjectedGradientTolerance":-1}``
153 GradientNormTolerance
154 This key indicates a limit value, leading to stop successfully the
155 iterative optimization process when the norm of the gradient is under this
156 limit. It is only used for non-constrained optimizers. The default is
157 1.e-5 and it is not recommended to change it.
159 Example : ``{"GradientNormTolerance":1.e-5}``
161 StoreSupplementaryCalculations
162 This list indicates the names of the supplementary variables that can be
163 available at the end of the algorithm. It involves potentially costly
164 calculations or memory consumptions. The default is a void list, none of
165 these variables being calculated and stored by default. The possible names
166 are in the following list: ["APosterioriCovariance", "BMA", "CostFunctionJ",
167 "CurrentState", "OMA", "OMB", "Innovation", "SigmaObs2",
168 "MahalanobisConsistency", "SimulatedObservationAtBackground",
169 "SimulatedObservationAtCurrentState", "SimulatedObservationAtOptimum",
170 "SimulationQuantiles"].
172 Example : ``{"StoreSupplementaryCalculations":["BMA","Innovation"]}``
175 This list indicates the values of quantile, between 0 and 1, to be estimated
176 by simulation around the optimal state. The sampling uses a multivariate
177 gaussian random sampling, directed by the *a posteriori* covariance matrix.
178 This option is useful only if the supplementary calculation
179 "SimulationQuantiles" has been chosen. The default is a void list.
181 Example : ``{"Quantiles":[0.1,0.9]}``
184 This key allow to give an integer in order to fix the seed of the random
185 generator used to generate the ensemble. A convenient value is for example
186 1000. By default, the seed is left uninitialized, and so use the default
187 initialization from the computer.
189 Example : ``{"SetSeed":1000}``
191 NumberOfSamplesForQuantiles
192 This key indicates the number of simulation to be done in order to estimate
193 the quantiles. This option is useful only if the supplementary calculation
194 "SimulationQuantiles" has been chosen. The default is 100, which is often
195 sufficient for correct estimation of common quantiles at 5%, 10%, 90% or
198 Example : ``{"NumberOfSamplesForQuantiles":100}``
200 SimulationForQuantiles
201 This key indicates the type of simulation, linear (with the tangent
202 observation operator applied to perturbation increments around the optimal
203 state) or non-linear (with standard observation operator applied to
204 perturbated states), one want to do for each perturbation. It changes mainly
205 the time of each elementary calculation, usually longer in non-linear than
206 in linear. This option is useful only if the supplementary calculation
207 "SimulationQuantiles" has been chosen. The default value is "Linear", and
208 the possible choices are "Linear" and "NonLinear".
210 Example : ``{"SimulationForQuantiles":"Linear"}``
212 Information and variables available at the end of the algorithm
213 +++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++
215 At the output, after executing the algorithm, there are variables and
216 information originating from the calculation. The description of
217 :ref:`section_ref_output_variables` show the way to obtain them by the method
218 named ``get`` of the variable "*ADD*" of the post-processing. The input
219 variables, available to the user at the output in order to facilitate the
220 writing of post-processing procedures, are described in the
221 :ref:`subsection_r_o_v_Inventaire`.
223 The unconditional outputs of the algorithm are the following:
226 *List of vectors*. Each element is an optimal state :math:`\mathbf{x}*` in
227 optimization or an analysis :math:`\mathbf{x}^a` in data assimilation.
229 Example : ``Xa = ADD.get("Analysis")[-1]``
232 *List of values*. Each element is a value of the error function :math:`J`.
234 Example : ``J = ADD.get("CostFunctionJ")[:]``
237 *List of values*. Each element is a value of the error function :math:`J^b`,
238 that is of the background difference part.
240 Example : ``Jb = ADD.get("CostFunctionJb")[:]``
243 *List of values*. Each element is a value of the error function :math:`J^o`,
244 that is of the observation difference part.
246 Example : ``Jo = ADD.get("CostFunctionJo")[:]``
248 The conditional outputs of the algorithm are the following:
250 APosterioriCovariance
251 *List of matrices*. Each element is an *a posteriori* error covariance
252 matrix :math:`\mathbf{A}*` of the optimal state.
254 Example : ``A = ADD.get("APosterioriCovariance")[-1]``
257 *List of vectors*. Each element is a vector of difference between the
258 background and the optimal state.
260 Example : ``bma = ADD.get("BMA")[-1]``
263 *List of vectors*. Each element is a usual state vector used during the
264 optimization algorithm procedure.
266 Example : ``Xs = ADD.get("CurrentState")[:]``
269 *List of vectors*. Each element is an innovation vector, which is in static
270 the difference between the optimal and the background, and in dynamic the
273 Example : ``d = ADD.get("Innovation")[-1]``
275 MahalanobisConsistency
276 *List of values*. Each element is a value of the Mahalanobis quality
279 Example : ``m = ADD.get("MahalanobisConsistency")[-1]``
282 *List of vectors*. Each element is a vector of difference between the
283 observation and the optimal state in the observation space.
285 Example : ``oma = ADD.get("OMA")[-1]``
288 *List of vectors*. Each element is a vector of difference between the
289 observation and the background state in the observation space.
291 Example : ``omb = ADD.get("OMB")[-1]``
294 *List of values*. Each element is a value of the quality indicator
295 :math:`(\sigma^o)^2` of the observation part.
297 Example : ``so2 = ADD.get("SigmaObs")[-1]``
299 SimulatedObservationAtBackground
300 *List of vectors*. Each element is a vector of observation simulated from
301 the background :math:`\mathbf{x}^b`.
303 Example : ``hxb = ADD.get("SimulatedObservationAtBackground")[-1]``
305 SimulatedObservationAtCurrentState
306 *List of vectors*. Each element is an observed vector at the current state,
307 that is, in the observation space.
309 Example : ``Ys = ADD.get("SimulatedObservationAtCurrentState")[-1]``
311 SimulatedObservationAtOptimum
312 *List of vectors*. Each element is a vector of observation simulated from
313 the analysis or optimal state :math:`\mathbf{x}^a`.
315 Example : ``hxa = ADD.get("SimulatedObservationAtOptimum")[-1]``
318 *List of vectors*. Each element is a vector corresponding to the observed
319 state which realize the required quantile, in the same order than the
320 quantiles required by the user.
322 Example : ``sQuantiles = ADD.get("SimulationQuantiles")[:]``
327 References to other sections:
328 - :ref:`section_ref_algorithm_Blue`
329 - :ref:`section_ref_algorithm_ExtendedBlue`
330 - :ref:`section_ref_algorithm_LinearityTest`
332 Bibliographical references: