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Jacobi and Gauss Seidel give a formula for xk in terms of x(k-1) call this xbasick
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Overrelaxation forms xSORk = ? xbasick + (1- ?)xbasic(k-1)
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Typically only 0 < ? < 2 is sensible and ? < 1 is relaxation 1 < ? < 2 is over relaxation
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It is "over" because if ? > 1, you go "further" in direction of new estimate than calculated
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In "relaxation", you conservatively, average prediction with old value
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Unfortunately, the best value of ? cannot be calculated except in simple cases and so SOR is not so reliable for general problems
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