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Gaussian Elimination with Partial Pivoting over Finite Fields (GEPPFF)

Input

An $n \times n$ matrix $A$ with entries over a finite field and an integer $l$.

Problem

What is the smallest row index in the $l^\text{th}$ column that is nonzero when Gaussian elimination with partial pivoting is performed on $A$?

Status

Open (Greenlaw, Hoover and Ruzzo [2]).

Remarks

Vavasis shows the analogous problem for unrestricted fields is $\P$-complete [1], see GEPP.

References

  1. S. Vavasis (1989). Gaussian elimination with pivoting is P-complete.
  2. Greenlaw, R., Hoover, H. J., and Ruzzo, W. L. (1995). Limits to Parallel Computation: P-Completeness Theory. Oxford University Press. Problem B.5.2.