View source for Verify the bounded discrepancy of an input sequence

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#!/usr/bin/env python
"""Erdos Discrepancy Problem sequence verification.

Verifies that discrepancy is bounded
for 1124-length sequence of +/-1.

file 1124_min.txt should contain:
+ - + + - - - - ...

by Michael Yang, 2010

"""
from __future__ import with_statement
from numpy import zeros, int8
SEQUENCE_LENGTH = 1124
fileInput = '1124_min.txt'

class DiscrepancyError(Exception):
    pass

def verifySequence(x, C=2, verbose=False):
    """verify discrepancy <= C

"""
    for i in range(SEQUENCE_LENGTH):
        inds = range(i,SEQUENCE_LENGTH,i+1)
        s = x[inds].sum()  # discrepancy
        if abs(s) > C:
            msg = 'd = %d has discrepancy %s'
            msg %= (i+1, s)
            raise DiscrepancyError(msg)
        if verbose: print i+1, s
    if verbose: print 'verified'
    return True

if __name__=='__main__':
    # load +/- sequence
    x = zeros(SEQUENCE_LENGTH, dtype = int8)
    with open(fileInput, 'r') as f:
        a = f.read()
    for i, side in enumerate(a.strip().split()):
        if side == '-':
            x[i] = -1
        elif side == '+':
            x[i] = 1
    assert i == SEQUENCE_LENGTH - 1
    isGood = verifySequence(x)
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