Update README

lifting/README.md

@@ -12,9 +12,9 @@ To produce the tables in the paper, the following tools and libraries were
 used. Different versions may produce slightly different outputs.
 
 - GNU Make, version 3.81
-- CMake, version 3.5.1
-- GCC, the GNU Compiler Collection, version 4.8.4
-- Ruby, version 1.9.3
+- CMake, version 3.7.2
+- GCC, the GNU Compiler Collection, version 6.3.0
+- Ruby, version 2.4.0
 - IBM® ILOG® CPLEX®, version 12.6
 
 Build instructions
@@ -35,16 +35,18 @@ Running the experiments
 3. Two CSV files will be generated inside the folder `lifting/benchmark/tables`,
 	corresponding to the two tables that appear in the paper.
 
+Modifying the instances
+-----------------------
+
 In order to run the experiments with a different set of instances,
 the file `lifting/benchmark/instances/filtered/all.txt` should be modified.
 Each line in this file describes the origin `f` and a lattice-free set `B`.
-The set `B` is described by the coordinates of its vertices. Since the generator
-only deals with maximal lattice-free sets, it is also necessary to specify the
-lattice-point in the relative interior of each facet of `B`. The format of the file
-is as follows:
+The set `B` is described by the coordinates of its vertices. Since the
+benchmark code only deals with maximal lattice-free sets, it is also necessary
+to specify the lattice-points that belong to each facet of `B`.
+If `n` is the number of facets, `v` is an n-by-2 matrix of doubles corresponding
+to the vertices and l is an n-by-2 matrix of doubles corresponding to the
+lattice-points, then each line of the file should be written as
 
 	f[0] f[1] n v[0][0] v[0][1] ... v[n-1][0] v[n-1][1] n l[0][0] l[0][1] ... l[n-1][0] l[n-1][1]
 
-where `n` is the number of facets, `v` is a n-by-2 matrix of doubles
-corresponding to the vertices and l is an n-by-2 matrix of doubles
-corresponding to the lattice-points.