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

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

Parameters:
codeword: ArrayLike

The codeword as either a \(n\)-length vector or \((N, n)\) matrix, where \(N\) is the number of codewords.

Shortened codes

For the shortened \([n-s,\ k-s,\ d]\) code (only applicable for systematic codes), pass \(n-s\) symbols into detect().

Returns:

A boolean scalar or \(N\)-length array indicating if errors were detected in the corresponding codeword.

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([ 3,  8, 12,  3,  2,  8,  2,  0,  3], order=2^4)

In [4]: c = rs.encode(m); c
Out[4]: GF([ 3,  8, 12,  3,  2,  8,  2,  0,  3,  1, 11,  6, 14, 14,  0], 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([13,  4,  1,  1,  9,  7], order=2^4)

In [8]: c[0:rs.d - 1] += e; c
Out[8]: GF([14, 12, 13,  2, 11, 15,  2,  0,  3,  1, 11,  6, 14, 14,  0], 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([13, 15, 10,  2,  5], order=2^4)

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

In [17]: c[0:rs.d - 1] += e; c
Out[17]: GF([ 1, 12,  2,  1, 15,  6,  0,  9,  7,  2, 14], 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([[ 0, 15,  3, 14,  0, 15,  8,  9,  1],
    [ 1,  4,  3, 13,  0,  2,  5, 10, 12],
    [13,  5,  1,  5, 11,  3,  9,  3, 12]], order=2^4)

In [22]: c = rs.encode(m); c
Out[22]: 
GF([[ 0, 15,  3, 14,  0, 15,  8,  9,  1,  9, 14, 10,  4,  1,  0],
    [ 1,  4,  3, 13,  0,  2,  5, 10, 12,  7,  7,  1,  7,  9,  6],
    [13,  5,  1,  5, 11,  3,  9,  3, 12,  9, 14, 14,  5,  7, 14]],
   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([[ 6, 15,  3, 14,  0, 15,  8,  9,  1,  9, 14, 10,  4,  1,  0],
    [ 5,  0,  3, 13,  0,  2,  5, 10, 12,  7,  7,  1,  7,  9,  6],
    [ 0, 12,  7,  0,  4, 15,  9,  3, 12,  9, 14, 14,  5,  7, 14]],
   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([[ 8, 10, 15,  6, 15],
    [10,  2,  2,  6,  2],
    [11,  1,  8,  8,  1]], order=2^4)

In [33]: c = rs.encode(m); c
Out[33]: 
GF([[ 8, 10, 15,  6, 15, 13,  3,  6,  7,  0,  3],
    [10,  2,  2,  6,  2,  9, 10,  6,  3, 13,  4],
    [11,  1,  8,  8,  1, 14,  3,  1,  7, 14,  4]], 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([[ 9, 10, 15,  6, 15, 13,  3,  6,  7,  0,  3],
    [ 4,  8,  2,  6,  2,  9, 10,  6,  3, 13,  4],
    [13,  4, 12,  1,  4,  6,  3,  1,  7, 14,  4]], order=2^4)

In [40]: rs.detect(c)
Out[40]: array([ True,  True,  True])