Stanislav Poslavsky

Rare test failure: `MultivariateResultantsTest.testZippel3_random_sparse_vars:276` https://circleci.com/api/v1.1/project/github/PoslavskySV/rings/454/output/104/0?file=true

https://circleci.com/gh/PoslavskySV/rings/447

LinearSolver: switch to Gauss-Bareiss elimination for certain problems over integral domains

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(to avoid many gcd calculations in some cases)

It is very simple and much faster then the current test in Z.

This can considerably speed up arithmetic in Z/p[x] for p > 2^64 and GF[x] (used quite often)

ZippelGCD rarely fails on some dense input.

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Test case: ```java @Test public void testSmallDomain6() throws Exception { IntegersZp64 ring = Rings.Zp64(3); MultivariatePolynomialZp64 a = MultivariatePolynomialZp64.parse("1 + a + 5*b + 7*c + d + 11*e + 13*f...

LinZip makes too many loop cycles (system is `UnderDetermied`) with Vandermonde powers (`(evaluationPoint) ^ (iTry)`). The answer will not be even obtained if `NUMBER_OF_UNDER_DETERMINED_RETRIES` is too small (each evaluation `(evaluationPoint)...

It may be faster than Algorithm 15.17 in _[J von zur Gathen, J Gerhard]_