galois.ReedSolomon.detect(codeword: ArrayLike) → bool_ | ndarray

Detects if errors are present in the Reed-Solomon codeword \(\mathbf{c}\).

The \([n, k, d]_q\) Reed-Solomon code has \(d_{min} = d\) minimum distance. It can detect up to \(d_{min}-1\) errors.

Parameters
codeword: ArrayLike

The codeword as either a \(n\)-length vector or \((N, n)\) matrix, where \(N\) is the number of codewords. For systematic codes, codeword lengths less than \(n\) may be provided for shortened codewords.

Returns

A boolean scalar or array indicating if errors were detected in the corresponding codeword True or not False.

Examples

Encode a single message using the \(\textrm{RS}(15, 9)\) code.

In [1]: rs = galois.ReedSolomon(15, 9)

In [2]: GF = rs.field

In [3]: m = GF.Random(rs.k); m
Out[3]: GF([ 2, 15, 15, 10,  9,  9,  4, 12, 13], order=2^4)

In [4]: c = rs.encode(m); c
Out[4]: GF([ 2, 15, 15, 10,  9,  9,  4, 12, 13,  5,  7,  8,  1,  8,  3], order=2^4)

Detect no errors in the valid codeword.

In [5]: rs.detect(c)
Out[5]: False

Detect \(d_{min}-1\) errors in the codeword.

In [6]: rs.d
Out[6]: 7

In [7]: e = GF.Random(rs.d - 1, low=1); e
Out[7]: GF([6, 3, 8, 1, 4, 8], order=2^4)

In [8]: c[0:rs.d - 1] += e; c
Out[8]: GF([ 4, 12,  7, 11, 13,  1,  4, 12, 13,  5,  7,  8,  1,  8,  3], order=2^4)

In [9]: rs.detect(c)
Out[9]: True

Encode a single message using the shortened \(\textrm{RS}(11, 5)\) code.

In [10]: rs = galois.ReedSolomon(15, 9)

In [11]: GF = rs.field

In [12]: m = GF.Random(rs.k - 4); m
Out[12]: GF([15, 13,  6,  2, 12], order=2^4)

In [13]: c = rs.encode(m); c
Out[13]: GF([15, 13,  6,  2, 12, 13,  2,  5,  5,  3,  6], order=2^4)

Detect no errors in the valid codeword.

In [14]: rs.detect(c)
Out[14]: False

Detect \(d_{min}-1\) errors in the codeword.

In [15]: rs.d
Out[15]: 7

In [16]: e = GF.Random(rs.d - 1, low=1); e
Out[16]: GF([10, 12,  7,  3, 14, 10], order=2^4)

In [17]: c[0:rs.d - 1] += e; c
Out[17]: GF([5, 1, 1, 1, 2, 7, 2, 5, 5, 3, 6], order=2^4)

In [18]: rs.detect(c)
Out[18]: True

Encode a matrix of three messages using the \(\textrm{RS}(15, 9)\) code.

In [19]: rs = galois.ReedSolomon(15, 9)

In [20]: GF = rs.field

In [21]: m = GF.Random((3, rs.k)); m
Out[21]: 
GF([[11, 12,  2, 11,  5,  0, 11,  1,  5],
    [ 0, 15, 15,  4, 10, 13,  2,  8,  8],
    [ 0, 14,  6,  3, 10, 12, 13,  5, 12]], order=2^4)

In [22]: c = rs.encode(m); c
Out[22]: 
GF([[11, 12,  2, 11,  5,  0, 11,  1,  5, 12, 13,  9, 13, 10,  9],
    [ 0, 15, 15,  4, 10, 13,  2,  8,  8, 12, 15, 11,  2,  3, 10],
    [ 0, 14,  6,  3, 10, 12, 13,  5, 12,  6,  9, 13,  9, 15, 13]],
   order=2^4)

Detect no errors in the valid codewords.

In [23]: rs.detect(c)
Out[23]: array([False, False, False])

Detect one, two, and \(d_{min}-1\) errors in the codewords.

In [24]: rs.d
Out[24]: 7

In [25]: c[0,0:1] += GF.Random(1, low=1)

In [26]: c[1,0:2] += GF.Random(2, low=1)

In [27]: c[2, 0:rs.d - 1] += GF.Random(rs.d - 1, low=1)

In [28]: c
Out[28]: 
GF([[ 5, 12,  2, 11,  5,  0, 11,  1,  5, 12, 13,  9, 13, 10,  9],
    [ 3,  6, 15,  4, 10, 13,  2,  8,  8, 12, 15, 11,  2,  3, 10],
    [ 5,  8, 14,  4,  0, 10, 13,  5, 12,  6,  9, 13,  9, 15, 13]],
   order=2^4)

In [29]: rs.detect(c)
Out[29]: array([ True,  True,  True])

Encode a matrix of three messages using the shortened \(\textrm{RS}(11, 5)\) code.

In [30]: rs = galois.ReedSolomon(15, 9)

In [31]: GF = rs.field

In [32]: m = GF.Random((3, rs.k - 4)); m
Out[32]: 
GF([[ 0,  1,  6, 10, 13],
    [ 6, 10,  9, 12,  0],
    [ 0,  1,  9, 12,  3]], order=2^4)

In [33]: c = rs.encode(m); c
Out[33]: 
GF([[ 0,  1,  6, 10, 13,  0, 14,  8,  8, 10, 10],
    [ 6, 10,  9, 12,  0,  7,  1, 15,  3,  7, 14],
    [ 0,  1,  9, 12,  3,  5,  9,  8,  2, 13,  3]], order=2^4)

Detect no errors in the valid codewords.

In [34]: rs.detect(c)
Out[34]: array([False, False, False])

Detect one, two, and \(d_{min}-1\) errors in the codewords.

In [35]: rs.d
Out[35]: 7

In [36]: c[0,0:1] += GF.Random(1, low=1)

In [37]: c[1,0:2] += GF.Random(2, low=1)

In [38]: c[2, 0:rs.d - 1] += GF.Random(rs.d - 1, low=1)

In [39]: c
Out[39]: 
GF([[ 7,  1,  6, 10, 13,  0, 14,  8,  8, 10, 10],
    [15,  3,  9, 12,  0,  7,  1, 15,  3,  7, 14],
    [11,  9,  6,  7, 15, 11,  9,  8,  2, 13,  3]], order=2^4)

In [40]: rs.detect(c)
Out[40]: array([ True,  True,  True])
Last update: Nov 10, 2022