Difference between revisions of "Example Fixed Sized Matrices"
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Line 2: | Line 2: | ||
External Resources: | External Resources: | ||
− | * [https://github.com/lessthanoptimal/ejml/blob/v0. | + | * [https://github.com/lessthanoptimal/ejml/blob/v0.41/examples/src/org/ejml/example/ExampleFixedSizedMatrix.java ExampleFixedSizedMatrix] |
* <disqus>Discuss this example</disqus> | * <disqus>Discuss this example</disqus> | ||
Line 16: | Line 16: | ||
*/ | */ | ||
public class ExampleFixedSizedMatrix { | public class ExampleFixedSizedMatrix { | ||
− | + | public static void main( String[] args ) { | |
− | public static void main( String | ||
// declare the matrix | // declare the matrix | ||
DMatrix3x3 a = new DMatrix3x3(); | DMatrix3x3 a = new DMatrix3x3(); | ||
Line 23: | Line 22: | ||
// Can assign values the usual way | // 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 | // most of the standard operations are support | ||
− | CommonOps_DDF3.transpose(a,b); | + | CommonOps_DDF3.transpose(a, b); |
b.print(); | b.print(); | ||
− | System.out.println("Determinant = "+ CommonOps_DDF3.det(a)); | + | System.out.println("Determinant = " + CommonOps_DDF3.det(a)); |
// matrix-vector operations are also supported | // matrix-vector operations are also supported | ||
// Constructors for vectors and matrices can be used to initialize its value | // 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(); | DMatrix3 result = new DMatrix3(); | ||
− | CommonOps_DDF3.mult(a,v,result); | + | CommonOps_DDF3.mult(a, v, result); |
// Conversion into DMatrixRMaj can also be done | // Conversion into DMatrixRMaj can also be done | ||
− | DMatrixRMaj dm = DConvertMatrixStruct.convert(a,null); | + | DMatrixRMaj dm = DConvertMatrixStruct.convert(a, null); |
dm.print(); | dm.print(); | ||
Line 58: | Line 57: | ||
// can then convert it back into a fixed matrix | // 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"); | System.out.println("Original simple matrix and converted fixed matrix"); |
Latest revision as of 07:37, 7 July 2021
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.
External Resources:
- ExampleFixedSizedMatrix
- <disqus>Discuss this example</disqus>
Example
/**
* 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++) {
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
CommonOps_DDF3.transpose(a, b);
b.print();
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();
CommonOps_DDF3.mult(a, v, result);
// Conversion into DMatrixRMaj can also be done
DMatrixRMaj dm = DConvertMatrixStruct.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
DMatrix3x3 fv = DConvertMatrixStruct.convert(sv.getDDRM(), (DMatrix3x3)null);
System.out.println("Original simple matrix and converted fixed matrix");
sv.print();
fv.print();
}
}