This paper deals with the GPL-stability of the Implicit Runge-Kutta methods
for the numerical solutions of the systems of delay differential equations. We fo
cus on the stability behaviour of the Implicit Runge-Kutta(IRK) methods in the
solutions of the following test systems with a delay term
y'(t)=Ly(t)+My(t-τ), t≥0,
y(t)=φ(t),t≤ 0,
where L, M are N×N complex matrices,τ> 0,φ(t) is a given vector function. We
shall show that the IRK methods is GPL-stable if and only if it is L-stable,when
we use the IRK methods to the test systems above.