GAP 4.8.9 installation with standard packages -- copy to your CoCalc project to get it
# ACEExample "big-hard" : enumeration of cosets of H in G,
# where |G| = 2^18.3, |G : H| = 6, using hard strategy.
#
local F, G, a, b, c, x, y, A, B, C;
# We define a group G of order 2^18.3 on 5 generators
F := FreeGroup("a","b","c","x","y");
a := F.1; b := F.2; c := F.3; x := F.4; y := F.5;
A := a^-1; B := b^-1; C := c^-1;
G := F / [a*B*C*b*a*c, b*A*C*b*a*a*c*A, a*c*c*A*A*B*a*b,
x^2, Comm(a,x), Comm(b,x), Comm(c,x),
y^3, Comm(a,y), Comm(b,y), Comm(c,y), Comm(x,y)];
return ACEfunc(
FreeGeneratorsOfFpGroup(G),
RelatorsOfFpGroup(G),
[a*B*C*b*a*c, b*A*C*b*a*a*c*A, a*c*c*A*A*B*a*b] # |G : H| = 6
# Options that don't affect the enumeration
: echo, enum := "G (order 2^18.3)", subg := "H (index 6)",
# Other options
hard, mend, ct := 2000, no := 11, pmod := 2, fill := 2,
dsiz := 15000, mess := 100000, wo := "2500k");