66 lines
1.4 KiB
Mathematica
66 lines
1.4 KiB
Mathematica
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function varargout = cabs(varargin)
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%cabs (overloaded)
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switch class(varargin{1})
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case 'double'
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varargout{1} = abs(varargin{1});
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case 'sdpvar'
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varargout{1} = InstantiateElementWise(mfilename,varargin{:});
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case 'char'
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operator = struct('convexity','convex','monotonicity','none','definiteness','positive','model','callback');
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operator.derivative = @derivative;
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operator.bounds = @bounds;
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operator.convexhull = @convexhull;
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varargout{1} = [];
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varargout{2} = operator;
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varargout{3} = varargin{3};
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otherwise
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error('SDPVAR/CABS called with CHAR argument?');
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end
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function df = derivative(x)
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df = zeros(length(x),1);
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df(x>0) = 1;
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df(x<0) = -1;
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% Bounding functions for the branch&bound solver
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function [L,U] = bounds(xL,xU)
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if xL <= 0 && xU >= 0
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L = 0;
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U = max(abs(xL),abs(xU));
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elseif xL >= 0
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L = xL;
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U = xU;
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else
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L = abs(xU);
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U = abs(xL);
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end
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function [Ax, Ay, b, K] = convexhull(xL,xU)
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fL = abs(xL);
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fU = abs(xU);
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if fL == fU || xL>=0
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Ax = -1;
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Ay = 1;
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b = 0;
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K.f = 1;
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K.l = 0;
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elseif xU<=0
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Ax = 1;
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Ay = 1;
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b = 0;
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K.f = 1;
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K.l = 0;
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elseif xL < 0 && xU > 0
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dfL = -1;
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dfU = 1;
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[Ax,Ay,b] = convexhullConvex(xL,xU,fL,fU,dfL,dfU);
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K = [];
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end
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