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gray cousins
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valbert4 committed Nov 23, 2023
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5 changes: 3 additions & 2 deletions codes/classical/bits/nonlinear/gray.yml
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A simple example is the case \(n=2\), also known as the \textit{Gray map}, which produces the ordering \(0\to 00\), \(1\to 01\), \(2\to 11\), and \(3\to 10\).
The Gray map differs in the last two numbers from the usual binary expansion of the natural numbers, which maps \(0\to 00\), \(1\to 01\), \(2\to 10\), and \(3\to 11\).
Layout out the Gray-map output strings counterclockwise on the corners of a 1D square, gray codes have been generalized such that nearest-neighbor strings differ by only one digit when the strings are arranged in higher-dimensional hypercubes \cite{doi:10.1002/j.1538-7305.1958.tb03887.x}.
Further generalizations called \textit{combinatorial Gray codes} \cite{doi:10.1137/0209013} refer to methods to generate organize combinatorial objects such that successive objects differ in some particular way. Particular \(q\)-ary extensions \cite{doi:10.1109/TSMCB.2012.2210706} of Gray codes may be useful in digital imaging and signal processing.
Gray codes have been generalized such that nearest-neighbor strings differ by only one digit when the strings are arranged in higher-dimensional hypercubes \cite{doi:10.1002/j.1538-7305.1958.tb03887.x}.
Further generalizations called \textit{combinatorial Gray codes} \cite{doi:10.1137/0209013} refer to methods to organize combinatorial objects such that successive objects differ in some particular way.
Particular \(q\)-ary extensions \cite{doi:10.1109/TSMCB.2012.2210706} of Gray codes may be useful in digital imaging and signal processing.
features:
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2 changes: 2 additions & 0 deletions codes/classical/bits/nonlinear/kerdock.yml
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cousins:
- code_id: quaternary_over_z4
detail: 'Kerdock codes can be seen, via the Gray map, as extended linear cyclic codes over \(\mathbb{Z}_4\), where the appended bit is a zero sum check \cite{doi:10.1109/18.312154,arxiv:math/0207208}.'
- code_id: gray
detail: 'Kerdock codes can be seen, via the Gray map, as extended linear cyclic codes over \(\mathbb{Z}_4\), where the appended bit is a zero sum check \cite{doi:10.1109/18.312154,arxiv:math/0207208}.'
- code_id: reed_muller
detail: 'Kerdock code is a subcode of a second-order RM Code \cite[pg. 457]{preset:MacSlo}.
It consists of a number of cosets of RM\((2,m)\) created by quotienting with RM\((1,m)\).'
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2 changes: 2 additions & 0 deletions codes/classical/bits/nonlinear/preparata.yml
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cousins:
- code_id: quaternary_over_z4
detail: 'Preparata codes can be seen, via the Gray map, as linear codes over \(\mathbb{Z}_4\) \cite{doi:10.1109/18.312154,arxiv:math/0207208}.'
- code_id: gray
detail: 'Preparata codes can be seen, via the Gray map, as linear codes over \(\mathbb{Z}_4\) \cite{doi:10.1109/18.312154,arxiv:math/0207208}.'
- code_id: quasi_perfect
detail: 'Punctured Preparata codes are quasi-perfect \cite[pg. 475]{preset:MacSlo}.'
- code_id: reed_muller
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2 changes: 2 additions & 0 deletions codes/classical/bits/nonlinear/sphere_packing/julin12.yml
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detail: 'Using Construction \(A\), the Julin-Golay codes yield non-lattice sphere-packings that hold records in 9 and 11 dimensions.'
- code_id: q-ary_over_zq
detail: 'Julin codes can be obtained from simple nonlinear codes over \(\mathbb{Z}_4\) using the Gray map \cite{doi:10.1007/BF01388558}.'
- code_id: gray
detail: 'Julin codes can be obtained from simple nonlinear codes over \(\mathbb{Z}_4\) using the Gray map \cite{doi:10.1007/BF01388558}.'


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2 changes: 2 additions & 0 deletions codes/classical/bits/reed_muller.yml
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detail: 'RM\(^*(r,m)\) codes are equivalent to subcodes of BCH codes of designed distance \(2^{m-r}-1\) while RM\((r,m)\) are subcodes of extended BCH codes of the same designed distance \cite[Ch. 13]{preset:MacSlo}.'
- code_id: quaternary_over_z4
detail: 'RM codes are images of linear quaternary codes over \(\mathbb{Z}_4\) under the Gray map \cite[Sec. 6.3]{preset:HKSrings}.'
- code_id: gray
detail: 'RM codes are images of linear quaternary codes over \(\mathbb{Z}_4\) under the Gray map \cite[Sec. 6.3]{preset:HKSrings}.'
- code_id: dual
detail: 'The codes RM\((r,m)\) and RM\((m-r-1,m)\) are dual to each other.'
- code_id: binary_duadic
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2 changes: 2 additions & 0 deletions codes/classical/rings/pentacode.yml
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cousins:
- code_id: best
detail: 'Codewords of the Best code can be obtained by applying the Gray map to the pentacode \cite[Sec. 2]{doi:10.1007/BF01388558}.'
- code_id: gray
detail: 'Codewords of the Best code can be obtained by applying the Gray map to the pentacode \cite[Sec. 2]{doi:10.1007/BF01388558}.'


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