[136] | 1 | #include <Eigen/Array>
|
---|
| 2 |
|
---|
| 3 | int main(int argc, char *argv[])
|
---|
| 4 | {
|
---|
| 5 | std::cout.precision(2);
|
---|
| 6 |
|
---|
| 7 | // demo static functions
|
---|
| 8 | Eigen::Matrix3f m3 = Eigen::Matrix3f::Random();
|
---|
| 9 | Eigen::Matrix4f m4 = Eigen::Matrix4f::Identity();
|
---|
| 10 |
|
---|
| 11 | std::cout << "*** Step 1 ***\nm3:\n" << m3 << "\nm4:\n" << m4 << std::endl;
|
---|
| 12 |
|
---|
| 13 | // demo non-static set... functions
|
---|
| 14 | m4.setZero();
|
---|
| 15 | m3.diagonal().setOnes();
|
---|
| 16 |
|
---|
| 17 | std::cout << "*** Step 2 ***\nm3:\n" << m3 << "\nm4:\n" << m4 << std::endl;
|
---|
| 18 |
|
---|
| 19 | // demo fixed-size block() expression as lvalue and as rvalue
|
---|
| 20 | m4.block<3,3>(0,1) = m3;
|
---|
| 21 | m3.row(2) = m4.block<1,3>(2,0);
|
---|
| 22 |
|
---|
| 23 | std::cout << "*** Step 3 ***\nm3:\n" << m3 << "\nm4:\n" << m4 << std::endl;
|
---|
| 24 |
|
---|
| 25 | // demo dynamic-size block()
|
---|
| 26 | {
|
---|
| 27 | int rows = 3, cols = 3;
|
---|
| 28 | m4.block(0,1,3,3).setIdentity();
|
---|
| 29 | std::cout << "*** Step 4 ***\nm4:\n" << m4 << std::endl;
|
---|
| 30 | }
|
---|
| 31 |
|
---|
| 32 | // demo vector blocks
|
---|
| 33 | m4.diagonal().block(1,2).setOnes();
|
---|
| 34 | std::cout << "*** Step 5 ***\nm4.diagonal():\n" << m4.diagonal() << std::endl;
|
---|
| 35 | std::cout << "m4.diagonal().start(3)\n" << m4.diagonal().start(3) << std::endl;
|
---|
| 36 |
|
---|
| 37 | // demo coeff-wise operations
|
---|
| 38 | m4 = m4.cwise()*m4;
|
---|
| 39 | m3 = m3.cwise().cos();
|
---|
| 40 | std::cout << "*** Step 6 ***\nm3:\n" << m3 << "\nm4:\n" << m4 << std::endl;
|
---|
| 41 |
|
---|
| 42 | // sums of coefficients
|
---|
| 43 | std::cout << "*** Step 7 ***\n m4.sum(): " << m4.sum() << std::endl;
|
---|
| 44 | std::cout << "m4.col(2).sum(): " << m4.col(2).sum() << std::endl;
|
---|
| 45 | std::cout << "m4.colwise().sum():\n" << m4.colwise().sum() << std::endl;
|
---|
| 46 | std::cout << "m4.rowwise().sum():\n" << m4.rowwise().sum() << std::endl;
|
---|
| 47 |
|
---|
| 48 | // demo intelligent auto-evaluation
|
---|
| 49 | m4 = m4 * m4; // auto-evaluates so no aliasing problem (performance penalty is low)
|
---|
| 50 | Eigen::Matrix4f other = (m4 * m4).lazy(); // forces lazy evaluation
|
---|
| 51 | m4 = m4 + m4; // here Eigen goes for lazy evaluation, as with most expressions
|
---|
| 52 | m4 = -m4 + m4 + 5 * m4; // same here, Eigen chooses lazy evaluation for all that.
|
---|
| 53 | m4 = m4 * (m4 + m4); // here Eigen chooses to first evaluate m4 + m4 into a temporary.
|
---|
| 54 | // indeed, here it is an optimization to cache this intermediate result.
|
---|
| 55 | m3 = m3 * m4.block<3,3>(1,1); // here Eigen chooses NOT to evaluate block() into a temporary
|
---|
| 56 | // because accessing coefficients of that block expression is not more costly than accessing
|
---|
| 57 | // coefficients of a plain matrix.
|
---|
| 58 | m4 = m4 * m4.transpose(); // same here, lazy evaluation of the transpose.
|
---|
| 59 | m4 = m4 * m4.transpose().eval(); // forces immediate evaluation of the transpose
|
---|
| 60 |
|
---|
| 61 | std::cout << "*** Step 8 ***\nm3:\n" << m3 << "\nm4:\n" << m4 << std::endl;
|
---|
| 62 | }
|
---|