It works but the output is broken :)

Semester 3/Assignments/templatesMatricesSample/src/main/java/edu/slcc/asdv/beans/MatrixOperations.java

@@ -35,6 +35,7 @@ public class MatrixOperations implements Serializable
         ArrayList<ArrayList<BigInteger>>  b =  convertToBigInteger(matrixA.getMatrix());
         ArrayList<ArrayList<String>>  c =  new ArrayList<ArrayList<String>>();
         c = convertToString(matrixManipulator.addParallel(a, b));
+        printArray(c);
        matrixC.setMatrixC( c );
        return "";
     }
@@ -44,6 +45,16 @@ public class MatrixOperations implements Serializable
         ArrayList<ArrayList<BigInteger>>  b =  convertToBigInteger(matrixA.getMatrix());
         ArrayList<ArrayList<String>>  c =  new ArrayList<ArrayList<String>>();
         c = convertToString(matrixManipulator.multiplyParallel(a, b));
+        printArray(c);
+       matrixC.setMatrixC( c );
+        return "";}
+        
+        public String subtract() {
+        ArrayList<ArrayList<BigInteger>>  a =  convertToBigInteger(matrixA.getMatrix());
+        ArrayList<ArrayList<BigInteger>>  b =  convertToBigInteger(matrixA.getMatrix());
+        ArrayList<ArrayList<String>>  c =  new ArrayList<ArrayList<String>>();
+        c = convertToString(matrixManipulator.subtractParallel(a, b));
+        printArray(c);
        matrixC.setMatrixC( c );
         return "";}
 
@@ -83,5 +94,36 @@ public class MatrixOperations implements Serializable
         }
         return string2DArray;
     }
+
+    /**
+     *
+     * @param matrix
+     * @return
+     */
+    public String printArray(ArrayList<ArrayList<String>> matrix) {
+        String output = "{\n";
+        for (int i = 0; i < matrix.size(); ++i) {
+            output += printSingleArray(matrix.get(i));
+            if ((matrix.size() - 1) > i) {
+                output += ",\n";
+            }
+        }
+        output += "\n}";
+        System.out.println(output);
+        return output;
+    }
+    
+    public String printSingleArray(ArrayList<String> matrix) {
+        String output = "\t{";
+        for (int i = 0; i < matrix.size(); ++i) {
+            output += matrix.get(i);
+            if ((matrix.size() - 1) > i) {
+                output += ", ";
+            }
+        }
+        output += "}";
+        return output;
+    }
+    
     
 }

Semester 3/Assignments/templatesMatricesSample/src/main/java/edu/slcc/asdv/beans/MenuBar.java

@@ -31,7 +31,7 @@ public class MenuBar implements Serializable
         matrixOperations.add();///adition of matrices
         System.out.println(matrixOperations.getMatrixC());
 
-        List<String> idsC = new ArrayList();
+        List<String> idsC = new ArrayList<>();
         idsC.add("formC");
         idsC.add("formC:datatableC");
         idsC.add("formC:datatableC:columnsC");
@@ -46,10 +46,10 @@ public class MenuBar implements Serializable
         System.out.println("menu multiply was called");
 
         System.out.println("menu bar multiply()");
-        matrixOperations.multiply();///adition of matrices
+        matrixOperations.multiply();///multiplication of matrices
         System.out.println(matrixOperations.getMatrixC());
 
-        List<String> idsC = new ArrayList();
+        List<String> idsC = new ArrayList<>();
         idsC.add("formC");
         idsC.add("formC:datatableC");
         idsC.add("formC:datatableC:columnsC");
@@ -60,10 +60,19 @@ public class MenuBar implements Serializable
 
     public void subtract()
     {
-        message(
+        System.out.println("menu subtract was called");
-                FacesMessage.SEVERITY_INFO,
+
-                "Not implemented.", "To be implemented."
+        System.out.println("menu bar subtract()");
-        );
+        matrixOperations.subtract();///subtraction of matrices
+        System.out.println(matrixOperations.getMatrixC());
+
+        List<String> idsC = new ArrayList<>();
+        idsC.add("formC");
+        idsC.add("formC:datatableC");
+        idsC.add("formC:datatableC:columnsC");
+        idsC.add("formC:datatableC:columnsC:inputTextC");
+        //idsC.add("form-menu");//:menuBar:submenu_matrices:menuitem_add");
+        PrimeFaces.current().ajax().update(idsC);
     }
 
    

Semester 3/Assignments/templatesMatricesSample/src/main/java/edu/slcc/asdv/bl/Matrices.java

@@ -33,10 +33,16 @@ public class Matrices implements Matrix
         return result;
     }
 
-
+    @Override
-
+    public ArrayList<ArrayList<BigInteger>> subtractParallel(ArrayList<ArrayList<BigInteger>> A, ArrayList<ArrayList<BigInteger>> B)
-
+    {
-
+        RecursiveTask<ArrayList<ArrayList<BigInteger>>> rt
+                = new Matrices.MatricesSubtraction(0, A.size() - 1, A, B);
+        ForkJoinPool pool = new ForkJoinPool();
+        ArrayList<ArrayList<BigInteger>> result = pool.invoke(rt);
+        return result;
+    }
+    
 
     static class MatricesAddition extends RecursiveTask<ArrayList<ArrayList<BigInteger>>>
     {
@@ -131,6 +137,18 @@ public class Matrices implements Matrix
         }
         return resultsOfMultiplications;
     }
+    
+    public static ArrayList<BigInteger> subtractLists(ArrayList<BigInteger> list1, ArrayList<BigInteger> list2)
+    {
+        ArrayList<BigInteger> resultsOfSubtraction = new ArrayList<BigInteger>();
+        for (int bi = 0; bi < list1.size();
+                ++bi)
+        {
+            resultsOfSubtraction.add(list1.get(bi).subtract(list2.get(bi)));
+        }
+        return resultsOfSubtraction;
+    }
+    
 
     public static ArrayList<ArrayList<BigInteger>> columnMajorOrderReversal(ArrayList<ArrayList<BigInteger>> b)
     {
@@ -170,6 +188,14 @@ public class Matrices implements Matrix
         return bd;
     }
 
+    public static BigInteger subtract(ArrayList<BigInteger> list) {
+        BigInteger bd = BigInteger.ZERO;
+        for (int bi = 0; bi < list.size(); bi++) {
+            bd = bd.subtract(list.get(bi));
+        }
+        return bd;
+    }
+    
     static class MatricesMultiplication extends RecursiveTask<ArrayList<ArrayList<BigInteger>>>
     {
 
@@ -261,5 +287,98 @@ public class Matrices implements Matrix
         }
 
     }
+    
+    static class MatricesSubtraction extends RecursiveTask<ArrayList<ArrayList<BigInteger>>>
+    {
+
+        ArrayList<ArrayList<BigInteger>> A;
+        ArrayList<ArrayList<BigInteger>> B;
+        ArrayList<ArrayList<BigInteger>> AxB;
+        final int HOW_MANY_ROWS_IN_PARALLEL = 3;//threshold
+        int startIndex;
+        int endIndex;
+
+        public MatricesSubtraction(int startIndex, int endIndex,
+                ArrayList<ArrayList<BigInteger>> A,
+                ArrayList<ArrayList<BigInteger>> B)
+        {
+            this.startIndex = startIndex;//start at this row of the matrix
+            this.endIndex = endIndex;//end at this row of the matrix
+            this.A = A;
+            this.B = B;
+            AxB = new ArrayList<ArrayList<BigInteger>>();
+
+        }
+
+        /**
+         * matrix 
+         * 1, 2, 3
+         * 4, 5, 6
+         *
+         * will be transformed to 
+         * 1, 4 
+         * 2, 5 
+         * 3, 6
+         *
+         * @param list
+         * @return
+         */
+        @Override
+        protected ArrayList<ArrayList<BigInteger>> compute()
+        {
+            //>>This is the addition of matrices in the IF.
+            //That is, HOW_MANY_ROWS_IN_PARALLEL from matrix A and HOW_MANY_ROWS_IN_PARALLEL from matrix B
+            if (this.endIndex - this.startIndex < HOW_MANY_ROWS_IN_PARALLEL)
+            {
+                ArrayList<ArrayList<BigInteger>> resultC = new ArrayList<ArrayList<BigInteger>>();
+                ArrayList<ArrayList<BigInteger>> bTransformed = columnMajorOrderReversal(B);
+
+                for (int biA = this.startIndex;
+                        biA <= this.endIndex;
+                        ++biA)
+                {
+                    ArrayList<BigInteger> rowA = A.get(biA);
+                    ArrayList<BigInteger> rowAxB = new ArrayList<BigInteger>();
+                    ArrayList<BigInteger> rowCalculation = new ArrayList<BigInteger>();
+                    for (int biB = 0;
+                            biB < bTransformed.size();
+                            ++biB)
+                    {
+                        ArrayList<BigInteger> rowB = bTransformed.get(biB);
+
+                        ArrayList<BigInteger> productsOfRow = subtractLists(rowA, rowB);
+                        BigInteger sumOfDifference = add(productsOfRow);
+                        rowCalculation.add(sumOfDifference);
+
+                    }
+                    resultC.add(rowCalculation);
+
+                }
+                return resultC;
+            }
+            else
+            {      //>> keep on FORKING the matrix until the 
+                //side of the matric is equal or less to HOW_MANY_ROWS_IN_PARALLEL
+
+                int mid = (this.startIndex + this.endIndex) / 2;
+                RecursiveTask<ArrayList<ArrayList<BigInteger>>> firstHalf
+                        = new MatricesMultiplication(this.startIndex, mid, A, B);
+
+                RecursiveTask<ArrayList<ArrayList<BigInteger>>> secondHalf
+                        = new MatricesMultiplication(mid + 1, this.endIndex, A, B);
+
+                firstHalf.fork();//this line will  invoke method compute
+                secondHalf.fork();///this line will  invoke method compute
+
+                //>> join what the FORKs returned from the IFs 
+                AxB.addAll(firstHalf.join());
+                AxB.addAll(secondHalf.join());
+
+                return AxB;
+            }
+        }
+
+    }
+    
 
 }

Semester 3/Assignments/templatesMatricesSample/src/main/java/edu/slcc/asdv/bl/Matrix.java

@@ -15,5 +15,7 @@ public interface Matrix
 {
     ArrayList<ArrayList<BigInteger>> addParallel(ArrayList<ArrayList<BigInteger>> A, ArrayList<ArrayList<BigInteger>> B);
     ArrayList<ArrayList<BigInteger>> multiplyParallel(ArrayList<ArrayList<BigInteger>> A, ArrayList<ArrayList<BigInteger>> B);
+    ArrayList<ArrayList<BigInteger>> subtractParallel(ArrayList<ArrayList<BigInteger>> A, ArrayList<ArrayList<BigInteger>> B);
+    
     
 }