59 lines
1.9 KiB
C++
59 lines
1.9 KiB
C++
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#include <cmath>
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#include <cstdint>
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#include <iostream>
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#include <vector>
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#include "grotto.hpp"
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// Haar and bior(5,3) lookup tables (Reis, Ugurbil, Wagh, Henry, de Vega,
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// PoPETs 2025, ePrint 2025/013). The grid is sigmoid on [0, 4), stored as
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// Q4.4. Depth 2 keeps the top 4 bits of a 6-bit index.
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//
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// c++ -std=c++17 -march=native -I include -I thirdparty examples/grotto/dwt_lut.cpp
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int main()
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{
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//! [dwt-lut]
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constexpr unsigned domain_bits = 6;
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constexpr unsigned fractional_bits = 4;
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constexpr unsigned depth = 2;
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auto samples = grotto::sample_dwt_signal(domain_bits, fractional_bits,
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[](double x) {
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return 1.0 / (1.0 + std::exp(-(x - 2.0)));
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});
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auto haar = grotto::make_haar_dwt_lut(samples, fractional_bits, depth);
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auto bior = grotto::make_bior53_dwt_lut(samples, fractional_bits, depth);
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// Haar is the mean of each block of 2^depth samples, then quantized.
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const std::uint64_t raw = 32;
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double block = 0;
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for (unsigned k = 0; k < 4; ++k)
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block += samples[(raw & ~std::uint64_t{3}) + k];
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const auto haar_expect = static_cast<std::int64_t>(
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std::floor(block / 4.0 * 16.0));
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// bior(5,3), lsb = 0: only the first tap, at index msb+2, divided by 2^j.
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const std::uint64_t msb = raw >> depth;
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const auto c0 = bior.coeff[(msb + 2) % bior.coeff.size()];
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const auto bior_at_32 = c0 / 4;
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// lsb = 1: both taps, weights (2^j - lsb) and lsb, then divide by 2^{2j}.
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const auto c1 = bior.coeff[(msb + 3) % bior.coeff.size()];
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const auto bior_at_33 = (c0 * 3 + c1) / 16;
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//! [dwt-lut]
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if (haar(raw) != haar_expect || haar(raw) != 8)
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{
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std::cerr << "haar lut\n";
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return 1;
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}
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if (bior(raw) != bior_at_32 || bior(33) != bior_at_33 || bior(raw) != 8)
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{
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std::cerr << "bior lut\n";
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return 1;
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}
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std::cout << haar(raw) << " " << bior(raw) << " " << bior(33) << "\n";
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return 0;
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}
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