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PolakHeSearchDirectionAndMeritFunction.cpp Go to the documentation of this file. /* ****************************************************************** ** ** OpenSees - Open System for Earthquake Engineering Simulation ** ** Pacific Earthquake Engineering Research Center ** ** ** ** ** ** (C) Copyright 2001, The Regents of the University of California ** ** All Rights Reserved. ** ** ** ** Commercial use of this program without express permission of the ** ** University of California, Berkeley, is strictly prohibited. See ** ** file 'COPYRIGHT' in main directory for information on usage and ** ** redistribution, and for a DISCLAIMER OF ALL WARRANTIES. ** ** ** ** Developed by: ** ** Frank McKenna (fmckenna@ce.berkeley.edu) ** ** Gregory L. Fenves (fenves@ce.berkeley.edu) ** ** Filip C. Filippou (filippou@ce.berkeley.edu) ** ** ** ** Reliability module developed by: ** ** Terje Haukaas (haukaas@ce.berkeley.edu) ** ** Armen Der Kiureghian (adk@ce.berkeley.edu) ** ** ** ** ****************************************************************** */ // $Revision: 1.2 $ // $Date: 2003/10/27 23:45:42 $ // $Source: /usr/local/cvs/OpenSees/SRC/reliability/analysis/direction/PolakHeSearchDirectionAndMeritFunction.cpp,v $ // // Written by Terje Haukaas (haukaas@ce.berkeley.edu) // #include <PolakHeSearchDirectionAndMeritFunction.h> #include <SearchDirection.h> #include <MeritFunctionCheck.h> #include <Vector.h> PolakHeSearchDirectionAndMeritFunction::PolakHeSearchDirectionAndMeritFunction(double pgamma, double pdelta) :SearchDirection(), MeritFunctionCheck() { gamma = pgamma; delta = pdelta; alpha = 0.0; } PolakHeSearchDirectionAndMeritFunction::~PolakHeSearchDirectionAndMeritFunction() { } Vector PolakHeSearchDirectionAndMeritFunction::getSearchDirection() { return searchDirection; } int PolakHeSearchDirectionAndMeritFunction::setAlpha(double palpha) { alpha = palpha; return 0; } int PolakHeSearchDirectionAndMeritFunction::computeSearchDirection( int stepNumber, Vector u, double gFunctionValue, Vector gradientInStandardNormalSpace) { // Advise the user if the start value of the limit-state function // is out of the 'ideal range' for the Polak-He algorithm if (stepNumber == 1) { if (gFunctionValue > 15.0 || gFunctionValue < 2.0) { opserr << "WARNING: The start value of the limit-state function is outside " << endln << " the ideal range for fastest convergence of the Polak-He algorithm. " << endln; } } // Compute elements of the A matrix double oneOverDelta = 1.0/delta; double a11 = oneOverDelta * (u ^ u); double a22 = oneOverDelta * (gradientInStandardNormalSpace ^ gradientInStandardNormalSpace); double a12 = oneOverDelta * (u ^ gradientInStandardNormalSpace); // Compute the elements of the b vector: double b1; if (gFunctionValue <= 0.0) { b1 = 0.0; } else { b1 = gFunctionValue; } double b2 = b1 - gFunctionValue; b1 = gamma*b1; // Compute factors of second order equation double a = 0.5*a11 + 0.5*a22 - a12; double b = b1 - b2 + a12 - a22; double c = 0.5*a22 + b2; // Find coordinates of minimum point [z1 z2] double z1, z2; if (a<0.0) { opserr << "ERROR: PolakHeSearchDirectionAndMeritFunction::computeSearchDirection() " << endln << " the quadratic term is negative! " << endln; return -1; } else if (a < 1.0e-9) { // Here the quadratic term is zero, so we use one of the endpoints double Fend1 = c; // x=0.0 double Fend2 = a+b+c; // x=1.0 if (Fend1 < Fend2) { z1 = 0.0; z2 = 1.0; thetaFunction = -Fend1; } else { z1 = 1.0; z2 = 0.0; thetaFunction = -Fend2; } } else { // The 'normal' case double x = -b/(2.0*a); z1 = x; z2 = 1.0 - x; thetaFunction = -(a*x*x + b*x + c); // Check if the minimum point is outside the 'triangle' if (z1 < 0.0 || z1 > 1.0 || z2 < 0.0 || z2 > 1.0 ) { // Use one of the endpoints double Fend1 = c; // x=0.0 double Fend2 = a+b+c; // x=1.0 if (Fend1 < Fend2) { z1 = 0.0; z2 = 1.0; thetaFunction = -Fend1; } else { z1 = 1.0; z2 = 0.0; thetaFunction = -Fend2; } } } // With the coordinates of the minimum point the direction now reads searchDirection = -z1*u - z2*gradientInStandardNormalSpace; return 0; } double PolakHeSearchDirectionAndMeritFunction::getMeritFunctionValue(Vector u, double g, Vector grad_G) { opserr << "WARNING: PolakHeSearchDirectionAndMeritFunction::getMeritFunctionValue() --" << endln << " no explicit merit function value is computed." << endln; return 0.0; } int PolakHeSearchDirectionAndMeritFunction::updateMeritParameters(Vector u, double g, Vector grad_G) { opserr << "WARNING: PolakHeSearchDirectionAndMeritFunction::updateMeritParameters() --" << endln << " no explicit merit function value is computed." << endln; return 0; } int PolakHeSearchDirectionAndMeritFunction::check(Vector u_old, double g_old, Vector grad_G_old, double stepSize, Vector stepDirection, double g_new) { // New point in standard normal space Vector u_new = u_old + stepSize*stepDirection; // Check that the factor alpha is set (since this is a dual purpose class...) if (alpha == 0.0) { opserr << "ERROR: PolakHeSearchDirectionAndMeritFunction::check()" << endln << " the alpha factor is not set! " << endln; } // Determine the 'g plus' value double g_old_plus; if (g_old <= 0.0 ) { g_old_plus = 0.0; } else { g_old_plus = g_old; } // Evaluate the 'merit' function double term1 = 0.5*(u_new^u_new) - 0.5*(u_old^u_old) - gamma * g_old_plus; double term2 = g_new - g_old_plus; double F; if (term1 > term2) { F = term1; } else { F = term2; } // Do the check if ( F <= (alpha*stepSize*thetaFunction) ) { return 0; // ok } else { return -1; // not ok } } Generated on Mon Oct 23 15:05:25 2006 for OpenSees by  1.5.0

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