diff --git a/src/main/java/ch/idsia/crema/preprocess/creators/CreateCPT.java b/src/main/java/ch/idsia/crema/preprocess/creators/CreateCPT.java
index 6c0a3109..837e4e51 100644
--- a/src/main/java/ch/idsia/crema/preprocess/creators/CreateCPT.java
+++ b/src/main/java/ch/idsia/crema/preprocess/creators/CreateCPT.java
@@ -5,6 +5,7 @@
 import ch.idsia.crema.factor.credal.linear.interval.IntervalFactorFactory;
 import ch.idsia.crema.utility.IndexIterator;
 
+import java.util.ArrayList;
 import java.util.Arrays;
 
 public class CreateCPT {
@@ -19,21 +20,29 @@ public class CreateCPT {
      */
     public double[] borders(double[] lower, double[] upper, Op operation) {
 
-        //shortcut in case the function is strictly monotone growing
-        //double[] extremes= new double[]{operation.execute(lower[0], upper[1]), operation.execute(upper[0], lower[1])};
-        //return Arrays.stream(extremes).sorted().toArray();
+        int DIM = (int) Math.pow(2, lower.length);
+        double[] results = new double[DIM];
 
-        double[] results = new double[2 * lower.length];
-        results[0] = operation.execute(lower[0], lower[1]);
-        results[1] = operation.execute(lower[0], upper[1]);
-        results[2] = operation.execute(upper[0], lower[1]);
-        results[3] = operation.execute(upper[0], upper[1]);
-
-        Arrays.sort(results);
-        double firstElement = results[0];
-        double lastElement = results[results.length - 1];
+        for (int i = 0; i < DIM; i++) {
+            StringBuilder binary = new StringBuilder(Integer.toBinaryString(i));
+            for(int j = binary.length(); j < lower.length; j++) {
+                binary.insert( 0, '0' );
+            }
+            ArrayList<Double> paramList = new ArrayList<>();
+
+            for(int j = 0; j < binary.length(); j++) {
+                if(binary.charAt(j) == '0') {
+                    paramList.add(lower[j]);
+                } else {
+                    paramList.add(upper[j]);
+                }
+            }
+            results[i] = operation.execute(paramList.stream().mapToDouble(Double::doubleValue).toArray());
+        }
 
-        return new double[]{firstElement, lastElement};
+        return new double[]{
+                Arrays.stream(results).min().isPresent()? Arrays.stream(results).min().getAsDouble(): 0.0,
+                Arrays.stream(results).max().isPresent()? Arrays.stream(results).max().getAsDouble(): 0.0};
     }
 
     /**
@@ -51,7 +60,7 @@ public IntervalFactor create(int childVar, int[] parentsVars, double[] childCuts
 
         // root nodes creation
         // add child node
-        int dimChild = childCuts.length + 1;
+        int dimChild = childCuts.length-1;
         Strides stridesChild = Strides.var(childVar, dimChild);
 
         // create domain
@@ -80,8 +89,12 @@ public IntervalFactor create(int childVar, int[] parentsVars, double[] childCuts
             //map the integers of the position of the childCuts
             int[] intervalNumber = Arrays.stream(intervalBorders).mapToInt(val -> whichPosition(childCuts, val)).toArray();
 
-            // the lower is set to an array of zeroes the upper is set to 1 in the position of the interval number
-            factory.set(new double[dimChild], createUpper(intervalNumber, dimChild), comb);
+            boolean allEqual = intervalNumber.length == 1 || Arrays.stream(intervalNumber).allMatch(t -> t == intervalNumber[0]);
+            if(allEqual){
+                factory.set(createArrayWithOneAtIndex(intervalNumber, dimChild), createArrayWithOneAtIndex(intervalNumber, dimChild), comb);
+            }else{
+                factory.set(new double[dimChild], createArrayWithOneAtIndex(intervalNumber, dimChild), comb);
+            }
             iterator.next();
         }
         return factory.get();
@@ -92,7 +105,7 @@ public IntervalFactor create(int childVar, int[] parentsVars, double[] childCuts
      * @param dim      dimension of the array to be generated
      * @return double array with 1.0 set for every interval value
      */
-    public double[] createUpper(int[] interval, int dim) {
+    public double[] createArrayWithOneAtIndex(int[] interval, int dim) {
         double[] upper = new double[dim];
 
         // we set to 1.0 all the element relative to the interval
diff --git a/src/main/java/ch/idsia/crema/preprocess/creators/Op.java b/src/main/java/ch/idsia/crema/preprocess/creators/Op.java
index 6c7bfef4..41f23b58 100644
--- a/src/main/java/ch/idsia/crema/preprocess/creators/Op.java
+++ b/src/main/java/ch/idsia/crema/preprocess/creators/Op.java
@@ -2,5 +2,5 @@
 
 @FunctionalInterface
 public interface Op {
-    double execute(double a, double b);
+    double execute(double... params);
 }
diff --git a/src/test/java/ch/idsia/crema/preprocess/creators/CreateCPTTest.java b/src/test/java/ch/idsia/crema/preprocess/creators/CreateCPTTest.java
index abe46e2e..2e5fecfe 100644
--- a/src/test/java/ch/idsia/crema/preprocess/creators/CreateCPTTest.java
+++ b/src/test/java/ch/idsia/crema/preprocess/creators/CreateCPTTest.java
@@ -19,26 +19,26 @@ public void testCreate() {
         double[] cutsBMI = new double[]{0.0, 15.0, 16, 18.5, 25.0, 30.0, 35.0, 40.0, 100.0};
 
         double[][] parents = new double[][]{cutsW, cutsH};
-        Op bmi = (w, h) -> w / h / h;
+        Op bmi = (double... num) -> num[0] / num[1] / num[1];
 
         IntervalFactor cpt = creator.create(2, new int[]{0, 1}, cutsBMI, parents, bmi);
         //System.out.println(cpt);
 
         // w1 and h1
-        assertArrayEquals(cpt.getLower(0, 0), new double[10]);
-        assertArrayEquals(cpt.getUpper(0, 0), creator.createUpper(new int[]{4}, 10));
+        assertArrayEquals(cpt.getLower(0, 0), creator.createArrayWithOneAtIndex(new int[]{4}, 8));
+        assertArrayEquals(cpt.getUpper(0, 0), creator.createArrayWithOneAtIndex(new int[]{4}, 8));
 
         // w2 and h1
-        assertArrayEquals(cpt.getLower(1, 0), new double[10]);
-        assertArrayEquals(cpt.getUpper(1, 0), creator.createUpper(new int[]{4, 5}, 10));
+        assertArrayEquals(cpt.getLower(1, 0), new double[8]);
+        assertArrayEquals(cpt.getUpper(1, 0), creator.createArrayWithOneAtIndex(new int[]{4, 5}, 8));
 
         // w5 and h6
-        assertArrayEquals(cpt.getLower(4, 5), new double[10]);
-        assertArrayEquals(cpt.getUpper(4, 5), creator.createUpper(new int[]{4}, 10));
+        assertArrayEquals(cpt.getLower(4, 5), creator.createArrayWithOneAtIndex(new int[]{4}, 8));
+        assertArrayEquals(cpt.getUpper(4, 5), creator.createArrayWithOneAtIndex(new int[]{4}, 8));
 
         // w12 and h9
-        assertArrayEquals(cpt.getLower(11, 8), new double[10]);
-        assertArrayEquals(cpt.getUpper(11, 8), creator.createUpper(new int[]{5, 6}, 10));
+        assertArrayEquals(cpt.getLower(11, 8), new double[8]);
+        assertArrayEquals(cpt.getUpper(11, 8), creator.createArrayWithOneAtIndex(new int[]{5, 6}, 8));
     }
 
     @Test
@@ -46,7 +46,7 @@ public void testBorders() {
         double[] parentIntervalLower = new double[]{55.0, 1.55};
         double[] parentIntervalUpper = new double[]{60.0, 1.60};
         //example of the BMI
-        Op bmi = (w, h) -> w / h / h;
+        Op bmi = (double... num) -> num[0] / num[1] / num[1];
 
         //bmi low = 21.48
         //bmi high = 24.97
@@ -69,9 +69,9 @@ public void testWhichPosition() {
     }
 
     @Test
-    public void testCreateUpper() {
+    public void testCreateArrayWithOneAtIndex() {
         int[] interval = new int[]{3, 4};
-        double[] result = creator.createUpper(interval, 4);
+        double[] result = creator.createArrayWithOneAtIndex(interval, 4);
         double[] expected = new double[]{.0, .0, 1.0, 1.0};
 
         assertArrayEquals(result, expected);