cvp / src / functions_for_cvp.sage @ ada40619
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| 1 | ada40619 | Serge Torres | def common_scaling_factor(precision, floatBasis, precisionFraction = None): |
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| 2 | ada40619 | Serge Torres | """ |
| 3 | ada40619 | Serge Torres | Compute the common scaling factor (a power of 2). |
| 4 | ada40619 | Serge Torres | The exponent is made of: |
| 5 | ada40619 | Serge Torres | - a fraction of the precision; |
| 6 | ada40619 | Serge Torres | - an integer depending on the smallest norm of the vectors of the basis. |
| 7 | ada40619 | Serge Torres | """ |
| 8 | ada40619 | Serge Torres | ## Set a default value for the precisionFraction to 1/2. |
| 9 | ada40619 | Serge Torres | if precisionFraction is None: |
| 10 | ada40619 | Serge Torres | precisionFraction = 1/2 |
| 11 | ada40619 | Serge Torres | ## Compute the norms of the vectors and get the smallest one. |
| 12 | ada40619 | Serge Torres | # Start with "oo" (+Infinty) |
| 13 | ada40619 | Serge Torres | minBasisVectsNorm = oo |
| 14 | ada40619 | Serge Torres | currentNorm = 0 |
| 15 | ada40619 | Serge Torres | for vect in floatBasis.rows(): |
| 16 | ada40619 | Serge Torres | currentNorm = vect.norm() |
| 17 | ada40619 | Serge Torres | if currentNorm < minBasisVectNorm: |
| 18 | ada40619 | Serge Torres | minBasisVectNorm = currentNorm |
| 19 | ada40619 | Serge Torres | powerForMinNorm = floor(log(minBasisVectsNorm)/log2) |
| 20 | ada40619 | Serge Torres | if powerForMinNorm < 0: |
| 21 | ada40619 | Serge Torres | return 2^(ceil(precision*precisionFraction) - powerFromMinNorm) |
| 22 | ada40619 | Serge Torres | else: |
| 23 | ada40619 | Serge Torres | return 2^(ceil(precision*precisionFraction)) |
| 24 | ada40619 | Serge Torres |