2 Copyright (C) 2008-2016 EDF R&D
4 This file is part of SALOME ADAO module.
6 This library is free software; you can redistribute it and/or
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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: DerivativeFreeOptimization
25 .. _section_ref_algorithm_DerivativeFreeOptimization:
27 Calculation algorithm "*DerivativeFreeOptimization*"
28 ----------------------------------------------------
32 in its present version, this algorithm is experimental, and so changes can be
33 required in forthcoming versions.
38 This algorithm realizes an estimation of the state of a system by minimization
39 of a cost function :math:`J` without gradient. It is a method that doesn't use
40 the derivatives of the cost function. It fall for example in the same category
41 then the :ref:`section_ref_algorithm_ParticleSwarmOptimization`.
43 This is an optimization method allowing for global minimum search of a general
44 error function :math:`J` of type :math:`L^1`, :math:`L^2` or :math:`L^{\infty}`,
45 with or without weights. The default error function is the augmented weighted
46 least squares function, classicaly used in data assimilation.
48 Optional and required commands
49 ++++++++++++++++++++++++++++++
51 .. index:: single: AlgorithmParameters
52 .. index:: single: Background
53 .. index:: single: BackgroundError
54 .. index:: single: Observation
55 .. index:: single: ObservationError
56 .. index:: single: ObservationOperator
57 .. index:: single: Minimizer
58 .. index:: single: MaximumNumberOfSteps
59 .. index:: single: MaximumNumberOfFunctionEvaluations
60 .. index:: single: StateVariationTolerance
61 .. index:: single: CostDecrementTolerance
62 .. index:: single: QualityCriterion
63 .. index:: single: StoreSupplementaryCalculations
65 The general required commands, available in the editing user interface, are the
69 *Required command*. This indicates the background or initial vector used,
70 previously noted as :math:`\mathbf{x}^b`. Its value is defined as a
71 "*Vector*" or a *VectorSerie*" type object.
74 *Required command*. This indicates the background error covariance matrix,
75 previously noted as :math:`\mathbf{B}`. Its value is defined as a "*Matrix*"
76 type object, a "*ScalarSparseMatrix*" type object, or a
77 "*DiagonalSparseMatrix*" type object.
80 *Required command*. This indicates the observation vector used for data
81 assimilation or optimization, previously noted as :math:`\mathbf{y}^o`. It
82 is defined as a "*Vector*" or a *VectorSerie* type object.
85 *Required command*. This indicates the observation error covariance matrix,
86 previously noted as :math:`\mathbf{R}`. It is defined as a "*Matrix*" type
87 object, a "*ScalarSparseMatrix*" type object, or a "*DiagonalSparseMatrix*"
91 *Required command*. This indicates the observation operator, previously
92 noted :math:`H`, which transforms the input parameters :math:`\mathbf{x}` to
93 results :math:`\mathbf{y}` to be compared to observations
94 :math:`\mathbf{y}^o`. Its value is defined as a "*Function*" type object or
95 a "*Matrix*" type one. In the case of "*Function*" type, different
96 functional forms can be used, as described in the section
97 :ref:`section_ref_operator_requirements`. If there is some control :math:`U`
98 included in the observation, the operator has to be applied to a pair
101 The general optional commands, available in the editing user interface, are
102 indicated in :ref:`section_ref_assimilation_keywords`. Moreover, the parameters
103 of the command "*AlgorithmParameters*" allows to choose the specific options,
104 described hereafter, of the algorithm. See
105 :ref:`section_ref_options_Algorithm_Parameters` for the good use of this
108 The options of the algorithm are the following:
111 This key allows to choose the optimization minimizer. The default choice is
112 "POWELL", and the possible ones are "POWELL" (modified Powell unconstrained
113 minimizer, see [Powell]_), "SIMPLEX" (simplex or Nelder-Mead unconstrained
114 minimizer, see [Nelder]_). It is recommended to stay with the default.
115 Remark: the default "POWELL" method perform a dual outer/inner loops
116 optimization, leading then to less control on the cost function evaluation
117 number because it is the outer loop limit than is controled. If precise
118 control on this cost function evaluation number is required, choose the
121 Example : ``{"Minimizer":"POWELL"}``
124 This key indicates the maximum number of iterations allowed for iterative
125 optimization. The default is 15000, which is very similar to no limit on
126 iterations. It is then recommended to adapt this parameter to the needs on
127 real problems. For some optimizers, the effective stopping step can be
128 slightly different of the limit due to algorithm internal control
131 Example : ``{"MaximumNumberOfSteps":50}``
133 MaximumNumberOfFunctionEvaluations
134 This key indicates the maximum number of evaluation of the cost function to
135 be optimized. The default is 15000, which is very similar to no limit on
136 iterations. The calculation can be over this limit when an outer
137 optimization loop has to be finished. It is strongly recommended to adapt
138 this parameter to the needs on real problems.
140 Example : ``{"MaximumNumberOfFunctionEvaluations":50}``
142 StateVariationTolerance
143 This key indicates the maximum relative variation of the state for stopping
144 by convergence on the state. The default is 1.e-4, and it is recommended to
145 adapt it to the needs on real problems.
147 Example : ``{"StateVariationTolerance":1.e-4}``
149 CostDecrementTolerance
150 This key indicates a limit value, leading to stop successfully the
151 iterative optimization process when the cost function decreases less than
152 this tolerance at the last step. The default is 1.e-7, and it is
153 recommended to adapt it to the needs on real problems.
155 Example : ``{"CostDecrementTolerance":1.e-7}``
158 This key indicates the quality criterion, minimized to find the optimal
159 state estimate. The default is the usual data assimilation criterion named
160 "DA", the augmented weighted least squares. The possible criteria has to be
161 in the following list, where the equivalent names are indicated by the sign
162 "=": ["AugmentedWeightedLeastSquares"="AWLS"="DA",
163 "WeightedLeastSquares"="WLS", "LeastSquares"="LS"="L2",
164 "AbsoluteValue"="L1", "MaximumError"="ME"].
166 Example : ``{"QualityCriterion":"DA"}``
168 StoreSupplementaryCalculations
169 This list indicates the names of the supplementary variables that can be
170 available at the end of the algorithm. It involves potentially costly
171 calculations or memory consumptions. The default is a void list, none of
172 these variables being calculated and stored by default. The possible names
173 are in the following list: ["CurrentState", "CostFunctionJ",
174 "CostFunctionJAtCurrentOptimum", "CurrentOptimum", "IndexOfOptimum",
175 "InnovationAtCurrentState", "BMA", "OMA", "OMB",
176 "SimulatedObservationAtBackground", "SimulatedObservationAtCurrentOptimum",
177 "SimulatedObservationAtCurrentState", "SimulatedObservationAtOptimum"].
179 Example : ``{"StoreSupplementaryCalculations":["BMA", "Innovation"]}``
181 Information and variables available at the end of the algorithm
182 +++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++
184 At the output, after executing the algorithm, there are variables and
185 information originating from the calculation. The description of
186 :ref:`section_ref_output_variables` show the way to obtain them by the method
187 named ``get`` of the variable "*ADD*" of the post-processing. The input
188 variables, available to the user at the output in order to facilitate the
189 writing of post-processing procedures, are described in the
190 :ref:`subsection_r_o_v_Inventaire`.
192 The unconditional outputs of the algorithm are the following:
195 *List of vectors*. Each element is an optimal state :math:`\mathbf{x}*` in
196 optimization or an analysis :math:`\mathbf{x}^a` in data assimilation.
198 Example : ``Xa = ADD.get("Analysis")[-1]``
201 *List of values*. Each element is a value of the error function :math:`J`.
203 Example : ``J = ADD.get("CostFunctionJ")[:]``
206 *List of values*. Each element is a value of the error function :math:`J^b`,
207 that is of the background difference part.
209 Example : ``Jb = ADD.get("CostFunctionJb")[:]``
212 *List of values*. Each element is a value of the error function :math:`J^o`,
213 that is of the observation difference part.
215 Example : ``Jo = ADD.get("CostFunctionJo")[:]``
218 *List of vectors*. Each element is a usual state vector used during the
219 optimization algorithm procedure.
221 Example : ``Xs = ADD.get("CurrentState")[:]``
223 The conditional outputs of the algorithm are the following:
225 SimulatedObservationAtBackground
226 *List of vectors*. Each element is a vector of observation simulated from
227 the background :math:`\mathbf{x}^b`.
229 Example : ``hxb = ADD.get("SimulatedObservationAtBackground")[-1]``
231 SimulatedObservationAtCurrentState
232 *List of vectors*. Each element is an observed vector at the current state,
233 that is, in the observation space.
235 Example : ``Ys = ADD.get("SimulatedObservationAtCurrentState")[-1]``
237 SimulatedObservationAtOptimum
238 *List of vectors*. Each element is a vector of observation simulated from
239 the analysis or optimal state :math:`\mathbf{x}^a`.
241 Example : ``hxa = ADD.get("SimulatedObservationAtOptimum")[-1]``
246 References to other sections:
247 - :ref:`section_ref_algorithm_ParticleSwarmOptimization`
249 Bibliographical references: