Example Fixed Sized Matrices - Revision history

Peter at 15:37, 7 July 2021

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Peter at 04:57, 5 November 2020

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Peter at 01:15, 19 May 2017

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Peter at 01:01, 10 August 2015

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Peter at 02:52, 1 April 2015

2015-04-01T02:52:03Z

Peter: Created page with "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..."

2015-03-22T05:56:13Z

Created page with "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..."

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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.

Code on GitHub:
* [https://github.com/lessthanoptimal/ejml/blob/master/examples/src/org/ejml/example/ExampleFixedSizedMatrix.java ExampleFixedSizedMatrix]

== Fixed Matrix Example ==

<syntaxhighlight lang="java">
/**
* 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
FixedMatrix3x3_64F a = new FixedMatrix3x3_64F();
FixedMatrix3x3_64F b = new FixedMatrix3x3_64F();

// Can assign values the usual way
for( int i = 0; i < 3; i++ ) {
for( int j = 0; j < 3; j++ ) {
a.set(i,j,i+j+1);
}
}

// 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
a.print();

// most of the standard operations are support
FixedOps3.transpose(a,b);
b.print();

System.out.println("Determinant = "+FixedOps3.det(a));

// matrix-vector operations are also supported
// Constructors for vectors and matrices can be used to initialize its value
FixedMatrix3_64F v = new FixedMatrix3_64F(1,2,3);
FixedMatrix3_64F result = new FixedMatrix3_64F();

FixedOps3.mult(a,v,result);

// Conversion into DenseMatrix64F can also be done
DenseMatrix64F dm = ConvertMatrixType.convert(a,null);

dm.print();

// 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
FixedMatrix3x3_64F fv = ConvertMatrixType.convert(sv.getMatrix(),(FixedMatrix3x3_64F)null);

System.out.println("Original simple matrix and converted fixed matrix");
sv.print();
fv.print();
}
}
</syntaxhighlight>

@@ Line 2: / Line 2: @@
 External Resources:
-* [https://github.com/lessthanoptimal/ejml/blob/v0.31/examples/src/org/ejml/example/ExampleFixedSizedMatrix.java ExampleFixedSizedMatrix]
+* [https://github.com/lessthanoptimal/ejml/blob/v0.41/examples/src/org/ejml/example/ExampleFixedSizedMatrix.java ExampleFixedSizedMatrix]
 * <disqus>Discuss this example</disqus>
@@ Line 16: / Line 16: @@
   */
 public class ExampleFixedSizedMatrix {
+     public static void main( String[] args ) {
          // declare the matrix
          DMatrix3x3 a = new DMatrix3x3();
@@ Line 23: / Line 22: @@
          // Can assign values the usual way
-         for( int i = 0; i < 3; i++ ) {
+         for (int i = 0; i < 3; i++) {
-             for( int j = 0; j < 3; j++ ) {
+             for (int j = 0; j < 3; j++) {
-                 a.set(i,j,i+j+1);
+                 a.set(i, j, i + j + 1);
+             }
+         }
@@ Line 37: / Line 36: @@
          // most of the standard operations are support
-         CommonOps_DDF3.transpose(a,b);
+         CommonOps_DDF3.transpose(a, b);
          b.print();
-         System.out.println("Determinant = "+ CommonOps_DDF3.det(a));
+         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 v = new DMatrix3(1, 2, 3);
          DMatrix3 result = new DMatrix3();
-         CommonOps_DDF3.mult(a,v,result);
+         CommonOps_DDF3.mult(a, v, result);
          // Conversion into DMatrixRMaj can also be done
-         DMatrixRMaj dm = DConvertMatrixStruct.convert(a,null);
+         DMatrixRMaj dm = DConvertMatrixStruct.convert(a, null);
          dm.print();
@@ Line 58: / Line 57: @@
          // can then convert it back into a fixed matrix
-         DMatrix3x3 fv = DConvertMatrixStruct.convert(sv.getDDRM(),(DMatrix3x3)null);
+         DMatrix3x3 fv = DConvertMatrixStruct.convert(sv.getDDRM(), (DMatrix3x3)null);
          System.out.println("Original simple matrix and converted fixed matrix");

@@ Line 50: / Line 50: @@
          // Conversion into DMatrixRMaj can also be done
-         DMatrixRMaj dm = ConvertDMatrixStruct.convert(a,null);
+         DMatrixRMaj dm = DConvertMatrixStruct.convert(a,null);
          dm.print();
@@ Line 58: / Line 58: @@
          // can then convert it back into a fixed matrix
-         DMatrix3x3 fv = ConvertDMatrixStruct.convert(sv.matrix_F64(),(DMatrix3x3)null);
+         DMatrix3x3 fv = DConvertMatrixStruct.convert(sv.getDDRM(),(DMatrix3x3)null);
          System.out.println("Original simple matrix and converted fixed matrix");

@@ Line 1: / Line 1: @@
 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.
-Code on GitHub:
+External Resources:
 * [https://github.com/lessthanoptimal/ejml/blob/v0.27/examples/src/org/ejml/example/ExampleFixedSizedMatrix.java ExampleFixedSizedMatrix]
 == Example ==