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Various speed improvements to polynomial factorization and the GAP meataxe #720

Merged
merged 7 commits into from
Apr 13, 2016
Merged

Various speed improvements to polynomial factorization and the GAP meataxe #720

merged 7 commits into from
Apr 13, 2016

Commits on Apr 9, 2016

  1. Use PositionNonZero in Matrix_OrderPolynomialInner 

    This affects computation of minimal and characteristic polynomials
    @fingolfin
    fingolfin committed Apr 9, 2016
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  2. meataxe: replace LinearCombinationVecs by matrix multiplication 

    For compressed matrices, this is much more efficient, and it should
never be slower.
    @fingolfin
    fingolfin committed Apr 9, 2016
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  3. meataxe: add two calls to ConvertToMatrixRep 

    Combined with the preceding commit, these give a substantial speed
up for certain meataxe examples.
    @fingolfin
    fingolfin committed Apr 9, 2016
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  4. speed up factorization of ff polys with large number of equal factors 

    factoring (x-1)^293 over GF(p) for small p is about 1.5 times faster;
over GF(2) even about 2 times faster
    @fingolfin
    fingolfin committed Apr 9, 2016
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  5. speed up QUOTREM_LAURPOLS_LISTS (and hence polynomial division) 

    We avoid multiplying operations that amount to no-ops, but still
require GAP to do work. This in turn speeds up factoring polynomials
like (x-1)^293 over small fields (over GF(2) it becomes 3 times faster).
    @fingolfin
    fingolfin committed Apr 9, 2016
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  6. meataxe: some whitespace / indention fixes

    @fingolfin
    fingolfin committed Apr 9, 2016
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  7. meataxe: avoid unnecessary polynomial divisions 

    The old code first used QuotRemLaurpols to perform a trial division;
if the remainder turned out to be zero, it computed the quotient again.
Instead, we simply use QuotRemLaurpols to compute quotient and remainder
in one go.
    @fingolfin
    fingolfin committed Apr 9, 2016
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