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| Poor polynomialsolve accuracy? http://forum.alglib.net/viewtopic.php?f=2&t=3861 |
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| Author: | pde [ Fri Aug 03, 2018 4:48 pm ] |
| Post subject: | Poor polynomialsolve accuracy? |
Using alglib.polynomialsolve from C# runtime version 2.0.50727: Polynomial coefficients: 1 0 4 0 6 0 4 0 1 Actual roots are (0, +/-1) x 4 but calculated roots are: -7.74748397136954E-05, +/-0.999922521609102 7.74739404654778E-05, +/-0.999922520701244 -7.74828498355251E-05, +/-1.00007747929019 7.74837490837565E-05, +/-1.00007747839946 This is not a completely artificial test, this polynomial cropped up when designing a 4th order Butterworth bandstop filter. Is this the expected accuracy of the polynomial solver? |
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