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Correct algorithm to pass testbench #90

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6ea5e28
Merge pull request #89 from Forceflow/dev
Forceflow Jun 16, 2026
69110d2
Fixed license badge
Forceflow Jun 16, 2026
5ca5746
fix compilation error due to type mismatch for template functions.
RechieKho Aug 15, 2026
72a2ea6
Use correct formatting in morton test.
RechieKho Aug 15, 2026
207399f
Regenerate LUTs.
RechieKho Aug 15, 2026
c09b12b
Fix decoder incorrect LUTs.
RechieKho Aug 16, 2026
8f9456b
Fix `compute3D_ET_LUT_encode`.
RechieKho Aug 16, 2026
008d63d
Fix forloop.
RechieKho Aug 16, 2026
d188b66
Fix morton2d by referring to morton3d.
RechieKho Aug 16, 2026
548a7c0
Fix `compute3D_ET_LUT_encode` to be logically similar to `compute2D_E…
RechieKho Aug 16, 2026
bb86c43
Use preshifted x as unshifted x, y, and z LUT.
RechieKho Aug 16, 2026
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2 changes: 1 addition & 1 deletion README.md
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Original file line number Diff line number Diff line change
@@ -1,5 +1,5 @@
# Libmorton v0.2.12
[![CMake](https://github.com/Forceflow/libmorton/actions/workflows/cmake.yml/badge.svg)](https://github.com/Forceflow/libmorton/actions/workflows/cmake.yml) [![license](https://img.shields.io/github/license/mashape/apistatus.svg)](https://opensource.org/licenses/MIT)
[![CMake](https://github.com/Forceflow/libmorton/actions/workflows/cmake.yml/badge.svg)](https://github.com/Forceflow/libmorton/actions/workflows/cmake.yml) [![License: MIT](https://img.shields.io/badge/License-MIT-yellow.svg)](https://opensource.org/licenses/MIT)

* Libmorton is a **C++ header-only library** with methods to efficiently encode/decode 64, 32 and 16-bit Morton codes and coordinates, in 2D and 3D. *Morton order* is also known as *Z-order* or *[the Z-order curve](https://en.wikipedia.org/wiki/Z-order_curve)*.
* Libmorton is a **lightweight and portable** library - the only dependencies are standard C++ headers. Architecture-specific optimizations are available.
Expand Down
89 changes: 67 additions & 22 deletions include/libmorton/morton2D.h
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Expand Up @@ -38,8 +38,21 @@ namespace libmorton {
unsigned int shift = (i - 1) * 8;
answer =
answer << 16 |
Morton2D_encode_y_256[(y >> shift) & EIGHTBITMASK] |
Morton2D_encode_x_256[(x >> shift) & EIGHTBITMASK];
Morton2D_encode_y_256_32[(y >> shift) & EIGHTBITMASK] |
Morton2D_encode_x_256_32[(x >> shift) & EIGHTBITMASK];
}
return answer;
}

template<typename morton, typename coord, typename = std::enable_if_t<std::is_same<coord, uint_fast64_t>::value>>
inline morton m2D_e_sLUT(const coord x, const coord y) {
morton answer = 0;
for (unsigned int i = sizeof(coord); i > 0; --i) {
unsigned int shift = (i - 1) * 8;
answer =
answer << 16 |
Morton2D_encode_y_256_64[(y >> shift) & EIGHTBITMASK] |
Morton2D_encode_x_256_64[(x >> shift) & EIGHTBITMASK];
}
return answer;
}
Expand All @@ -52,22 +65,36 @@ namespace libmorton {
unsigned int shift = (i - 1) * 8;
answer =
answer << 16 |
(Morton2D_encode_x_256[(y >> shift) & EIGHTBITMASK] << morton(1)) |
(Morton2D_encode_x_256[(x >> shift) & EIGHTBITMASK]);
(Morton2D_encode_x_256_32[(y >> shift) & EIGHTBITMASK] << morton(1)) |
(Morton2D_encode_x_256_32[(x >> shift) & EIGHTBITMASK]);
}
return answer;
}

template<typename morton, typename coord, typename = std::enable_if_t<std::is_same<coord, uint_fast64_t>::value>>
inline morton m2D_e_LUT(const coord x, const coord y) {
morton answer = 0;
for (unsigned int i = sizeof(coord); i > 0; --i) {
unsigned int shift = (i - 1) * 8;
answer =
answer << 16 |
(Morton2D_encode_x_256_64[(y >> shift) & EIGHTBITMASK] << morton(1)) |
(Morton2D_encode_x_256_64[(x >> shift) & EIGHTBITMASK]);
}
return answer;
}

// HELPER METHOD for Early Termination LUT Encode
template<typename morton, typename coord>
inline morton compute2D_ET_LUT_encode(const coord c, const coord *LUT) {
template<typename morton, typename coord, typename lutT>
inline morton compute2D_ET_LUT_encode(const coord c, const lutT *LUT) {
unsigned long maxbit = 0;
if (findFirstSetBit<coord>(c, &maxbit) == 0) { return 0; }
// highest byte index containing any set bit
int highest_byte = static_cast<int>((maxbit + 1) / 8);
morton answer = 0;
unsigned int i = 0;
while (maxbit >= i) {
answer |= ((morton)LUT[(c >> i) & EIGHTBITMASK]) << i * 2;
i += 8;
for (int i = highest_byte; i >= 0; --i) {
unsigned int shift = i * 8;
answer = (answer << 16) | static_cast<morton>(LUT[(c >> shift) & EIGHTBITMASK]);
}
return answer;
}
Expand All @@ -77,16 +104,34 @@ namespace libmorton {
// Figuring this out is probably too costly in most cases.
template<typename morton, typename coord>
inline morton m2D_e_sLUT_ET(const coord x, const coord y) {
morton answer_x = compute2D_ET_LUT_encode<morton, coord>(x, Morton2D_encode_x_256);
morton answer_y = compute2D_ET_LUT_encode<morton, coord>(y, Morton2D_encode_y_256);
morton answer_x = compute2D_ET_LUT_encode<morton, coord, uint_fast32_t>(x, Morton2D_encode_x_256_32);
morton answer_y = compute2D_ET_LUT_encode<morton, coord, uint_fast32_t>(y, Morton2D_encode_y_256_32);
return answer_y | answer_x;
}

template<typename morton, typename coord, typename = std::enable_if_t<std::is_same<coord, uint_fast64_t>::value>>
inline morton m2D_e_sLUT_ET(const coord x, const coord y) {
morton answer_x = compute2D_ET_LUT_encode<morton, coord, uint_fast64_t>(x, Morton2D_encode_x_256_64);
morton answer_y = compute2D_ET_LUT_encode<morton, coord, uint_fast64_t>(y, Morton2D_encode_y_256_64);
return answer_y | answer_x;
}

// ENCODE 2D Morton code : LUT (Early termination version)
template<typename morton, typename coord>
inline morton m2D_e_LUT_ET(const coord x, const coord y) {
morton answer_x = compute2D_ET_LUT_encode<morton, coord>(x, Morton2D_encode_x_256);
morton answer_y = compute2D_ET_LUT_encode<morton, coord>(y, Morton2D_encode_x_256);
morton answer_x = compute2D_ET_LUT_encode<morton, coord, uint_fast32_t>(x, Morton2D_encode_x_256_32);
// This is because `Morton2D_encode_(y|z)_256_*` is basically just `Morton3D_encode_x_256_*` with some pre-shifting.
// And we don't want any pre-shifting in this case.
morton answer_y = compute2D_ET_LUT_encode<morton, coord, uint_fast32_t>(y, Morton2D_encode_x_256_32);
return (answer_y << 1) | answer_x;
}

template<typename morton, typename coord, typename = std::enable_if_t<std::is_same<coord, uint_fast64_t>::value>>
inline morton m2D_e_LUT_ET(const coord x, const coord y) {
morton answer_x = compute2D_ET_LUT_encode<morton, coord, uint_fast64_t>(x, Morton2D_encode_x_256_64);
// This is because `Morton2D_encode_(y|z)_256_*` is basically just `Morton3D_encode_x_256_*` with some pre-shifting.
// And we don't want any pre-shifting in this case.
morton answer_y = compute2D_ET_LUT_encode<morton, coord, uint_fast64_t>(y, Morton2D_encode_x_256_64);
return (answer_y << 1) | answer_x;
}

Expand Down Expand Up @@ -176,15 +221,15 @@ namespace libmorton {
// DECODE 2D Morton code : Shifted LUT
template<typename morton, typename coord>
inline void m2D_d_sLUT(const morton m, coord& x, coord& y) {
x = morton2D_DecodeCoord_LUT256<morton, coord>(m, Morton2D_decode_x_256, 0);
y = morton2D_DecodeCoord_LUT256<morton, coord>(m, Morton2D_decode_y_256, 0);
x = morton2D_DecodeCoord_LUT256<morton, coord>(m, Morton2D_decode_preshifted_x_256, 0);
y = morton2D_DecodeCoord_LUT256<morton, coord>(m, Morton2D_decode_preshifted_y_256, 0);
}

// DECODE 2D 64-bit morton code : LUT
template<typename morton, typename coord>
inline void m2D_d_LUT(const morton m, coord& x, coord& y) {
x = morton2D_DecodeCoord_LUT256<morton, coord>(m, Morton2D_decode_x_256, 0);
y = morton2D_DecodeCoord_LUT256<morton, coord>(m, Morton2D_decode_x_256, 1);
y = morton2D_DecodeCoord_LUT256<morton, coord>(m, Morton2D_decode_y_256, 1);
}

// DECODE 2D Morton code : Shifted LUT (early termination)
Expand All @@ -197,8 +242,8 @@ namespace libmorton {
unsigned int shiftback = 0;
while (firstbit_location > i) {
morton m_shifted = (m >> i) & EIGHTBITMASK;
x |= (coord)Morton2D_decode_x_256[m_shifted] << shiftback;
y |= (coord)Morton2D_decode_y_256[m_shifted] << shiftback;
x |= (coord)Morton2D_decode_preshifted_x_256[m_shifted] << shiftback;
y |= (coord)Morton2D_decode_preshifted_y_256[m_shifted] << shiftback;
shiftback += 4;
i += 8;
}
Expand All @@ -214,7 +259,7 @@ namespace libmorton {
unsigned int shiftback = 0;
while (firstbit_location > i) {
x |= (coord)Morton2D_decode_x_256[(m >> i) & EIGHTBITMASK] << shiftback;
y |= (coord)Morton2D_decode_x_256[(m >> (i + 1)) & EIGHTBITMASK] << shiftback;
y |= (coord)Morton2D_decode_y_256[(m >> (i + 1)) & EIGHTBITMASK] << shiftback;
shiftback += 4;
i += 8;
}
Expand Down Expand Up @@ -257,7 +302,7 @@ namespace libmorton {
inline void m2D_d_for(const morton m, coord& x, coord& y) {
x = 0; y = 0;
unsigned int checkbits = sizeof(morton) * 4;
for (unsigned int i = 0; i <= checkbits; ++i) {
for (unsigned int i = 0; i < checkbits; ++i) {
morton selector = 1;
unsigned int shift_selector = 2 * i;
x |= (m & (selector << shift_selector)) >> i;
Expand All @@ -271,7 +316,7 @@ namespace libmorton {
x = 0; y = 0;
unsigned long firstbit_location = 0;
if (!findFirstSetBit<morton>(m, &firstbit_location)) return;
float defaultbits = sizeof(morton) * 4;
float defaultbits = (sizeof(morton) * 8) / 2;
unsigned int checkbits = static_cast<unsigned int>(std::min(defaultbits, firstbit_location / 2.0f));
for (unsigned int i = 0; i <= checkbits; ++i) {
morton selector = 1;
Expand Down
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