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polynomial: use correct coefficients for newtons

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Danny Robson 2015-01-29 15:38:32 +11:00
parent 57d5538717
commit 4d12dabb5f
1 changed files with 14 additions and 8 deletions
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polynomial.cpp
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@ -24,6 +24,10 @@
#include <limits> #include <limits>
#include <cmath> #include <cmath>
#include <iostream>
static const size_t NEWTON_ITERATIONS = 1u;
//----------------------------------------------------------------------------- //-----------------------------------------------------------------------------
namespace util { namespace polynomial { namespace util { namespace polynomial {
@ -130,19 +134,21 @@ namespace util { namespace polynomial {
for (auto &i: s) for (auto &i: s)
i -= sub; i -= sub;
// Run an iteration of Newtons method to make the results slightly // Run some iterations of Newtons method to make the results slightly
// more accurate, they're a little loose straight out of the bat. // more accurate, they're a little loose straight out of the bat.
const float da = 3; const float da = 3 * _a;
const float db = 2 * a; const float db = 2 * _b;
const float dc = b; const float dc = 1 * _c;
for (auto &i: s) { for (auto &i: s) {
for (size_t j = 0; j < NEWTON_ITERATIONS; ++j) {
float deriv = da * i * i + db * i + dc; float deriv = da * i * i + db * i + dc;
if (almost_zero (deriv)) if (almost_zero (deriv))
continue; continue;
i = i - eval (coeffs, i) / deriv; i = i - eval (coeffs, i) / deriv;
} }
}
return s; return s;
} }