converters.py

著名的ldpc编解码的资料及源代码

"""

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     Development;  Mitsubishi Electric Research Laboratories (MERL), 201
     Broadway, Cambridge, MA   02139 or <[e-mail]>.        
                                                                               
     IN NO EVENT SHALL MERL BE LIABLE TO ANY PARTY FOR DIRECT, INDIRECT, 
     SPECIAL, INCIDENTAL, OR CONSEQUENTIAL DAMAGES, INCLUDING LOST        
     PROFITS, ARISING OUT OF THE USE OF THIS SOFTWARE AND ITS 
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     MERL SPECIFICALLY DISCLAIMS ANY WARRANTIES, INCLUDING, BUT NOT
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     FOR A PARTICULAR PURPOSE.  THE SOFTWARE PROVIDED HEREUNDER IS ON AN
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"""

"""
The converters package contains various routines to convert from
one representation of a code to another.

Type print converters.__dict__.keys() for a list of provided functions.
"""

def AlistToNKH(alistFileName):
    """
    Convert a parity check matrix in alist format in the file alistFileName
    to (N,K,H) format where N is the block length, K is the degrees of
    freedom and H is the parity check matrix represented as a list of rows.

    The alist format is used by Mackay and collaborators in their software.

    NOTE: you probably want to use AlistToNKEL if you want to create
    an LDPCCode or DualLDPDCode object based on an alist.
    """

    fd = open(alistFileName)
    data = fd.read().split('\n')

    line = data[0].split()
    (N,M) = (int(line[0]),int(line[1]))
    K = N-M
    H = [0]*M
    for j in range(M):
        H[j] = [0]*N

    i = 0
    for line in data[(4+N):(4+M+N)]:
        for item in line.split():
            H[i][int(item)-1] = 1
        i = i + 1

    return (N,K,H)


    
def AlistToNKEL(alistFileName):
    """
    Convert a parity check matrix in alist format in the file alistFileName
    to (N,K,E,L) format where N is the block length, K is the degrees of
    freedom, L is a list of links, and E is the total number of edges.

    The alist format is used by Mackay and collaborators in their software.
    """

    fd = open(alistFileName)
    data = fd.read().split('\n')

    line = data[0].split()
    (N,M) = (int(line[0]),int(line[1]))
    K = N-M
    L = [0]*M
    E = 0

    i = 0
    for line in data[(4+N):(4+M+N)]:
        L[i] = map(lambda x: int(x)-1,line.split())
        E = E + len(L[i])
        i = i + 1

    return (N,K,E,L)

def LinkArrayToMatrix(N,linkArray):
    H = [0]*len(linkArray)
    i=0
    for row in linkArray:
        H[i] = [0]*N
        for item in row:
            H[i][item] = 1
        i = i+1
    return H
    
def CountEdgesInLinkArray(linkArray):
    """
    CountEdgesInLinkArray(linkArray):
    Count number of edges in linkArray.  This is useful for getting
    the E parameter required by LDPCCode and DualLDPCCode.
    """
    result = 0
    for row in linkArray:
        result = result + len(row)
    return result