Linear Algebra Example
Example 7 – Linear Algebra
FILENAME: example7.cpp
Program:
/*
* This example shows how to use the class RWGenFact<T>
* to do linear algebra with double precision matrices.
*/
// Include the RWGenFact<T> class header file:
#include <rw/math/genfact.h>
// Include the double precision matrix header file:
#include <rw/math/genmat.h>
#include <iostream>
// Initial data for the vectors:
const double adata[] = {-3.0, 2.0, 1.0, 8.0, -7.0,
9.0, 5.0, 4.0, -6.0};
const double arhs[] = {6.0, 9.0, 1.0};
int main()
{
// Construct a test matrix and print it out:
RWGenMat<double> testmat(adata,3,3);
std::cout << "test matrix:\n" << testmat << "\n";
/*
* Calculate and print the inverse.
* Note that a type conversion occurs:
* testmat is converted to type RWGenFact<double>
* before the inverse is computed.
*/
std::cout << "inverse:\n" << inverse(testmat);
// Now construct an RWGenFact<double> from the matrix:
RWGenFact<double> LUtest(testmat);
// Once constructed, LUtest may be reused as required.
// Find the determinant:
std::cout << "\ndeterminant\n" << determinant(LUtest)
<< std::endl;
// Solve the linear system testmat*x = rhs:
RWMathVec<double> rhs(arhs, 3);
RWMathVec<double> x = solve(LUtest, rhs);
std::cout << "solution:\n" << x << "\n";
}
Sample Input:
None required.
Sample Output (note that the exact numbers depend on machine precision):
test matrix:
3X3
[
-3 8 5
2 -7 4
1 9 -6
]
inverse:
3X3
[
0.025532 0.395745 0.285106
0.068085 0.055319 0.093617
0.106383 0.148936 0.021277
]
determinant:
235
solution:
[
4 1 2
]
