#20493: Rank of random matrices over GF(2) is bounded (again)
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Reporter: kedlaya | Owner:
Type: defect | Status: new
Priority: major | Milestone: sage-7.2
Component: linear algebra | Resolution:
Keywords: random matrices, rank, | Merged in:
pseudorandom numbers | Reviewers:
Authors: | Work issues:
Report Upstream: N/A | Commit:
Branch: | Stopgaps: todo
Dependencies: |
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Comment (by kedlaya):
The relevant code fragment from
`sage.matrix.matrix_mod2_dense.Matrix_mod2_dense.randomize` appears to be:
{{{
assert(sizeof(m4ri_word) == 8)
mask = __M4RI_LEFT_BITMASK(self._entries.ncols % m4ri_radix)
for i from 0 <= i < self._nrows:
for j from 0 <= j < self._entries.width:
# for portability we get 32-bit twice rather than 64-bit once
low = gmp_urandomb_ui(rstate.gmp_state, 32)
high = gmp_urandomb_ui(rstate.gmp_state, 32)
self._entries.rows[i][j] = m4ri_swap_bits( ((<unsigned long
long>high)<<32) | (<unsigned long long>low) )
self._entries.rows[i][self._entries.width - 1] &= mask
}}}
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Ticket URL: <http://trac.sagemath.org/ticket/20493#comment:1>
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