Statistiques
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cvp / src / cvp-function.sage @ 08e8e462

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def common_scaling_factor(precision, floatBasis, precisionFraction = None):
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   """
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   Compute the common scaling factor (a power of 2).
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   The exponent is made of:
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       - a fraction of the precision;
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       - an integer depending on the smallest norm of the vectors of the basis.
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   """
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   ## Set a default value for the precisionFraction to 1/2.
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   if precisionFraction is None:
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       precisionFraction = 1/2
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   ## Compute the norms of the vectors and get the smallest one.
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   #  Start with  "oo" (+Infinty)
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   minBasisVectsNorm = oo
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   currentNorm = 0
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   for vect in floatBasis.rows():
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       currentNorm = vect.norm()
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       if currentNorm < minBasisVectNorm:
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           minBasisVectNorm = currentNorm
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   powerForMinNorm = floor(log(minBasisVectsNorm)/log2)
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   if powerForMinNorm < 0:
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       return 2^(ceil(precision*precisionFraction) - powerFromMinNorm)
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   else:
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       return 2^(ceil(precision*precisionFraction))
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