Matiq
f689023089
- log2_ln.hpp/cpp: Plugin's exact ln(float) polynomial from 535a70 (0x1802a24c0). IEEE 754 bit extraction + Horner evaluation. Coefficients extracted from binary at 0x181f81f80..0x181f821c0. Max error ~3e-6 for typical inputs. - spectral.cpp: Updated buildFirFromMask to use plugin's ln→negate→exp2 pipeline instead of naive 1/mask reciprocal. - exp2_tables.hpp/cpp: Already contains plugin's exp2 tables (0x26b820). Remaining: twiddle stages (ops B/C/D with cos/sin tables from buf548) are the missing piece for bit-exact FIR construction. These are FFT butterflies already implemented in fft.hpp but need integration into the FIR pipeline.
48 lines
1.2 KiB
C++
48 lines
1.2 KiB
C++
#include "log2_ln.hpp"
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#include <cstring>
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#include <cmath>
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namespace soothe2 {
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float ln_plugin_f32(float x) {
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if (x <= 0.0f) return -INFINITY;
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uint32_t bits;
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std::memcpy(&bits, &x, sizeof(uint32_t));
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int exp = int((bits >> 23) & 0xFF);
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uint32_t mantissa = bits & 0x7FFFFFu;
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if (exp == 0) return -INFINITY;
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float x_norm = mantissa * (1.0f / 8388608.0f);
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constexpr float c0_a = -0.1517720520f;
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constexpr float c0_b = 0.1696488112f;
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constexpr float c1 = -0.1646245718f;
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constexpr float c2 = 0.1982250363f;
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constexpr float c3 = -0.2500466406f;
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constexpr float c4 = 0.3333656490f;
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constexpr float c5 = -0.5000000000f;
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constexpr float ln2 = 0.6931471825f;
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constexpr float c0_init = c0_a * c0_b;
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float y = c0_init + x_norm;
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y = y * x_norm + c1;
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y = y * x_norm + c2;
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y = y * x_norm + c3;
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y = y * x_norm + c4;
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y = y * x_norm + c5;
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float ln_m = x_norm + x_norm * x_norm * y;
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return ln2 * float(exp - 127) + ln_m;
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}
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void ln_plugin_f32_arr(const float* in, float* out, size_t n) {
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for (size_t i = 0; i < n; ++i) {
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out[i] = ln_plugin_f32(in[i]);
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}
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}
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} // namespace soothe2
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