Epidemic Genetic Algorithm for Solving Inverse Problems: Parallel Algorithms

Author(s):  
Sabrina B. M. Sambatti ◽  
Haroldo F. de Campos Velho ◽  
Leonardo D. Chiwiacowsky
2009 ◽  
Vol 11 (1) ◽  
pp. 51-64 ◽  
Author(s):  
Xin Jin ◽  
G. (Kumar) Mahinthakumar ◽  
Emily M. Zechman ◽  
Ranji S. Ranjithan

Finding the location and concentration of groundwater contaminant sources typically requires the solution of an inverse problem. A parallel hybrid optimization framework that uses genetic algorithms (GA) coupled with local search approaches (GA-LS) has been developed previously to solve groundwater inverse problems. In this study, the identification of an emplaced source at the Borden site is carried out as a test problem using this optimization framework by using a Real Genetic Algorithm (RGA) as the GA approach and a Nelder–Mead simplex as the LS approach. The RGA results showed that the minimum objective function did not always correspond to the minimum solution error, indicating a possible non-uniqueness issue. To address this problem, a procedure to identify maximally different starting points for LS is introduced. When measurement or model errors are non-existent or minimal it is shown that one of these starting points leads to the true solution. When these errors are significant, this procedure leads to multiple possible solutions that could be used as a basis for further investigation. Metrics of mean and standard deviation of objective function values was adopted to evaluate the possible solutions. A new selection criterion based on these metrics is suggested to find the best alternative. This suggests that this alternative generation procedure could be used to address the non-uniqueness of similar inverse problems. A potential limitation of this approach is the application to a wide class of problems, as verification has not been performed with a large number of test cases or other inverse problems. This remains a topic for future work.


Geophysics ◽  
1997 ◽  
Vol 62 (5) ◽  
pp. 1524-1532 ◽  
Author(s):  
Andrew Curtis ◽  
Roel Snieder

The better conditioned an inverse problem is, the more independent pieces of information may be transferred from the data to the model solution, and the less independent prior information must be added to resolve trade offs. We present a practical measure of conditioning that may be calculated swiftly even for large inverse problems. By minimizing this measure, a genetic algorithm can be used to find a model parameterization that gives the best conditioned inverse problem. We illustrate the method by finding an optimal, irregular cell parameterization for a cross‐borehole tomographic example with a given source‐receiver geometry. Using the final parameterization, the inverse problem is almost a factor of three better conditioned than that using an average random parameterization. In addition, this method requires little additional programming when solving a linearized inverse problem. Hence, the improvement in conditioning and corresponding increase in independent information available for the model solution essentially come for free.


Volume 4 ◽  
2004 ◽  
Author(s):  
Keith A. Woodbury ◽  
Courtney Graham ◽  
John Baker ◽  
Charles Karr

The ill-posed nature of inverse problems suggests that a solution be obtained through an optimization method. Genetic algorithms (GAs) effectively locate the global optimum, and are therefore an appealing technique to solve inverse problems. GAs mimic biological evolution, refining a set of solutions until the best solution is found. In this report, a genetic algorithm is developed and demonstrated based on a simple problem of determining the equation of a straight line. Then the GA is modified and implemented to estimate the temperature distribution in a gas based on the measured infrared tranmissivity distribution. The ulitimate task of this inverse method will be determination of the gas composition based on these transmissivity measurements.


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