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Pseudo-inverse op_constraint

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This commit is contained in:
Clemens Eisenhofer 2023-01-03 17:47:54 +01:00
parent 84a5ec221f
commit 79e7380ffc
10 changed files with 144 additions and 47 deletions
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4
src/util/rational.cpp
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@ -154,7 +154,7 @@ bool rational::mult_inverse(unsigned num_bits, rational & result) const {
}
/**
* Compute multiplicative pseudo-inverse modulo 2^num_bits:
* Compute the smallest multiplicative pseudo-inverse modulo 2^num_bits:
*
* mod(n * n.pseudo_inverse(bits), 2^bits) == 2^k,
* where k is maximal such that 2^k divides n.
@ -167,7 +167,7 @@ rational rational::pseudo_inverse(unsigned num_bits) const {
SASSERT(!n.is_zero()); // TODO: or we define pseudo-inverse of 0 as 0.
unsigned const k = n.trailing_zeros();
rational const odd = machine_div2k(n, k);
VERIFY(odd.mult_inverse(num_bits, result));
VERIFY(odd.mult_inverse(num_bits - k, result));
SASSERT_EQ(mod(n * result, rational::power_of_two(num_bits)), rational::power_of_two(k));
return result;
}