# DenseMatrix/cxx_main.cpp

This is an example of how to use the Teuchos::SerialDenseMatrix class.

```#include "Teuchos_SerialDenseMatrix.hpp"
#include "Teuchos_Version.hpp"

int main(int argc, char* argv[])
{
cout << Teuchos::Teuchos_Version() << endl << endl;

// Creating a double-precision matrix can be done in several ways:
// Create an empty matrix with no dimension
Teuchos::SerialDenseMatrix<int,double> Empty_Matrix;
// Create an empty 3x4 matrix
Teuchos::SerialDenseMatrix<int,double> My_Matrix( 3, 4 );
// Basic copy of My_Matrix
Teuchos::SerialDenseMatrix<int,double> My_Copy1( My_Matrix ),
// (Deep) Copy of principle 3x3 submatrix of My_Matrix
My_Copy2( Teuchos::Copy, My_Matrix, 3, 3 ),
// (Shallow) Copy of 2x3 submatrix of My_Matrix
My_Copy3( Teuchos::View, My_Matrix, 2, 3, 1, 1 );

// The matrix dimensions and strided storage information can be obtained:
int rows = My_Copy3.numRows();  // number of rows
int cols = My_Copy3.numCols();  // number of columns
int stride = My_Copy3.stride(); // storage stride

// Matrices can change dimension:
Empty_Matrix.shape( 3, 3 );      // size non-dimensional matrices
My_Matrix.reshape( 3, 3 );       // resize matrices and save values

// Filling matrices with numbers can be done in several ways:
My_Matrix.random();             // random numbers
My_Copy1.putScalar( 1.0 );      // every entry is 1.0
My_Copy2(1,1) = 10.0;           // individual element access
Empty_Matrix = My_Matrix;       // copy My_Matrix to Empty_Matrix

// Basic matrix arithmetic can be performed:
Teuchos::SerialDenseMatrix<int,double> My_Prod( 3, 2 );
// Matrix multiplication ( My_Prod = 1.0*My_Matrix*My_Copy^T )
My_Prod.multiply( Teuchos::NO_TRANS, Teuchos::TRANS,
1.0, My_Matrix, My_Copy3, 0.0 );
My_Copy2 += My_Matrix;         // Matrix addition
My_Copy2.scale( 0.5 );         // Matrix scaling

// The pointer to the array of matrix values can be obtained:
double* My_Array = My_Matrix.values();   // pointer to matrix values
double* My_Column = My_Matrix[2];        // pointer to third column values

// The norm of a matrix can be computed:
double norm_one = My_Matrix.normOne();        // one norm
double norm_inf = My_Matrix.normInf();        // infinity norm
double norm_fro = My_Matrix.normFrobenius();  // frobenius norm

// Matrices can be compared:
// Check if the matrices are equal in dimension and values
if (Empty_Matrix == My_Matrix) {
cout<< "The matrices are the same!" <<endl;
}
// Check if the matrices are different in dimension or values
if (My_Copy2 != My_Matrix) {
cout<< "The matrices are different!" <<endl;
}

// A matrix can be sent to the output stream:
cout<< My_Matrix << endl;

return 0;
}
```

Generated on Thu Sep 18 12:41:17 2008 for Teuchos - Trilinos Tools Package by  1.3.9.1