Re: list equation

*To*: mathgroup at smc.vnet.net*Subject*: [mg121973] Re: list equation*From*: Simon <simonjtyler at gmail.com>*Date*: Fri, 7 Oct 2011 04:50:51 -0400 (EDT)*Delivered-to*: l-mathgroup@mail-archive0.wolfram.com*References*: <j6jpek$me8$1@smc.vnet.net>*Reply-to*: comp.soft-sys.math.mathematica at googlegroups.com

Using SameTest is a lot slower than sticking to the default, so you could try lst = Tuples[Range[50], 2]; lstnew = Union[Sort /@ lst] which is about 6000 times faster than your Union[lst, SameTest -> (#1 == Reverse[#2] &)] Easier still would just be to construct Flatten[Table[{i, j}, {i, 1, 100}, {j, i, 100}], 1] which is about twice as fast again.