This pathway does not produce any ATP, this pathway does not replace glycolysis, it runs simultaneously to glycolysis and is only initiated with an increased concentration of sugar phosphates.  One believed purpose of the methylglyoxal pathway is to help release the stress of elevated sugar phosphate concentration.  Also when methylglyoxal is formed from DHAP, an inorganic phosphate is given off which can be used to replenish a low concentration of needed inorganic phosphate.  The methylglyoxal pathway is a rather dangerous tactic, both because less energy is produced and a toxic compound, methylglyoxal is formed. ([http://mic.sgmjournals.org/cgi/reprint/151/3/707 Weber] 715).