Example Fixed Sized Matrices

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Array access adds a significant amount of overhead to matrix operations. A fixed sized matrix gets around that issue by having each element in the matrix be a variable in the class. EJML provides support for fixed sized matrices and vectors up to 6x6, at which point it loses its advantage. The example below demonstrates how to use a fixed sized matrix and convert to other matrix types in EJML.

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 * In some applications a small fixed sized matrix can speed things up a lot, e.g. 8 times faster.  One application
 * which uses small matrices is graphics and rigid body motion, which extensively uses 3x3 and 4x4 matrices.  This
 * example is to show some examples of how you can use a fixed sized matrix.
 * @author Peter Abeles
public class ExampleFixedSizedMatrix {

    public static void main( String args[] ) {
        // declare the matrix
        DMatrix3x3 a = new DMatrix3x3();
        DMatrix3x3 b = new DMatrix3x3();

        // Can assign values the usual way
        for( int i = 0; i < 3; i++ ) {
            for( int j = 0; j < 3; j++ ) {

        // Direct manipulation of each value is the fastest way to assign/read values
        a.a11 = 12;
        a.a23 = 64;

        // can print the usual way too

        // most of the standard operations are support

        System.out.println("Determinant = "+ CommonOps_DDF3.det(a));

        // matrix-vector operations are also supported
        // Constructors for vectors and matrices can be used to initialize its value
        DMatrix3 v = new DMatrix3(1,2,3);
        DMatrix3 result = new DMatrix3();


        // Conversion into DMatrixRMaj can also be done
        DMatrixRMaj dm = DConvertMatrixStruct.convert(a,null);


        // This can be useful if you need do more advanced operations
        SimpleMatrix sv = SimpleMatrix.wrap(dm).svd().getV();

        // can then convert it back into a fixed matrix
        DMatrix3x3 fv = DConvertMatrixStruct.convert(sv.getDDRM(),(DMatrix3x3)null);

        System.out.println("Original simple matrix and converted fixed matrix");