Off topic, but ...
(%i1) load(linalg);
(%o1) c:/maxima/share/maxima/5.9.2.19cvs/share/linearalgebra/linalg.mac
(%i2) mm[i,j] := 1/(x + i + j)$
(%i3) m : genmatrix(mm,4,4)$
(%i4) showtime : all$
Evaluation took 0.00 seconds (0.00 elapsed)
(%i5) lu_factor(m)$
Evaluation took 32.33 seconds (32.33 elapsed)
Convert to CRE
(%i6) lu_factor(m,crering)$
Evaluation took 00.40 seconds (00.40 elapsed)
In general, ratmx controls such behavior---linalg ignores this flag, but
allows you to do the same thing using the optional second argument.
Barton