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a8b9109cc8
but non-identity matrix l1 0 0 0 .... 0 l2 0 0 .... 0 0 l3 0 ... . . . . . . . . . And apply the multishift CG to it. Sum the poles and residues. Insist that this be the same as the exactly taken square root where l1,l2,l3 >= 0.
29 lines
800 B
C++
29 lines
800 B
C++
#ifndef MULTI_SHIFT_FUNCTION
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#define MULTI_SHIFT_FUNCTION
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namespace Grid {
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class MultiShiftFunction {
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public:
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int order;
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std::vector<RealD> poles;
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std::vector<RealD> residues;
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std::vector<RealD> tolerances;
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RealD norm;
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RealD lo,hi;
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MultiShiftFunction(int n,RealD _lo,RealD _hi): poles(n), residues(n), lo(_lo), hi(_hi) {;};
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RealD approx(RealD x);
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void csv(std::ostream &out);
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void gnuplot(std::ostream &out);
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MultiShiftFunction(AlgRemez & remez,double tol,bool inverse) :
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order(remez.getDegree()),
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tolerances(remez.getDegree(),tol),
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poles(remez.getDegree()),
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residues(remez.getDegree())
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{
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remez.getBounds(lo,hi);
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if ( inverse ) remez.getIPFE (&residues[0],&poles[0],&norm);
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else remez.getPFE (&residues[0],&poles[0],&norm);
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}
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};
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}
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#endif
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