  We present the results of two-dimensional magnetohydrodynamical numerical
simulations of relativistic magnetic reconnection, with particular emphasis on
the dynamics of Petschek-type configurations with high Lundquist numbers, S ~
10^5-10^8. The numerical scheme adopted, allowing for unprecedented accuracy
for this type of calculations, is based on high order finite volume and
discontinuous Galerkin methods as recently proposed by Dumbser & Zanotti
(2009). The possibility of producing high Lorentz factors is discussed, by
studying the effects produced on the dynamics by different magnetization and
resistivity regimes. We show that Lorentz factors close to ~4 can be produced
for a plasma magnetization parameter sigma=20. Moreover, we find that the
Sweet-Parker layers are unstable, generating secondary magnetic islands, but
only for S>S_c~10^8, much larger than what is reported in the Newtonian regime.
