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Alternate low pass filter option

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This commit is contained in:
Peter Boyle 2020-01-03 05:29:09 -05:00
parent aa920aa532
commit ba40a3f763
1 changed files with 18 additions and 0 deletions
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18
Grid/algorithms/approx/Chebyshev.h
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@ -94,6 +94,24 @@ public:
Coeffs.assign(0.,order); Coeffs.assign(0.,order);
Coeffs[order-1] = 1.; Coeffs[order-1] = 1.;
}; };
// PB - more efficient low pass drops high modes above the low as 1/x uses all Chebyshev's.
// Similar kick effect below the threshold as Lanczos filter approach
void InitLowPass(RealD _lo,RealD _hi,int _order)
{
lo=_lo;
hi=_hi;
order=_order;
if(order < 2) exit(-1);
Coeffs.resize(order);
for(int j=0;j<order;j++){
RealD k=(order-1.0);
RealD s=std::cos( j*M_PI*(k+0.5)/order );
Coeffs[j] = s * 2.0/order;
}
};
void Init(RealD _lo,RealD _hi,int _order, RealD (* func)(RealD)) void Init(RealD _lo,RealD _hi,int _order, RealD (* func)(RealD))
{ {