Ginkgo: The ginkgo-ranges program (original) (raw)
The ranges and accessor example..
| Table of contents | |
|---|---|
| Introduction About the example The commented program | Results Comments about programming and debugging The plain program |
Introduction
About the example
The commented program
a utility function for printing the factorization on screen
template
{
std::cout << std::setprecision(2) << std::fixed;
std::cout << "L = [";
for (int i = 0; i < A.length(0); ++i) {
std::cout << "\n ";
for (int j = 0; j < A.length(1); ++j) {
std::cout << (i > j ? A(i, j) : (i == j) * 1.) << " ";
}
}
std::cout << "\n]\n\nU = [";
for (int i = 0; i < A.length(0); ++i) {
std::cout << "\n ";
for (int j = 0; j < A.length(1); ++j) {
std::cout << (i <= j ? A(i, j) : 0.) << " ";
}
}
std::cout << "\n]" << std::endl;
}
int main(int argc, char* argv[])
{
using ValueType = double;
using IndexType = int;
Print version information
Create some test data, add some padding just to demonstrate how to use it with ranges. clang-format off
ValueType data[] = {
2., 4., 5., -1.0,
4., 11., 12., -1.0,
6., 24., 24., -1.0
};
clang-format on
Create a 3-by-3 range, with a 2D row-major accessor using data as the underlying storage. Set the stride (a.k.a. "LDA") to 4.
use the LU factorization routine defined above to factorize the matrix
print the factorization on screen
Results
This is the expected output:
L = [
1.00 0.00 0.00
2.00 1.00 0.00
3.00 4.00 1.00
]
U = [
2.00 4.00 5.00
0.00 3.00 2.00
0.00 0.00 1.00
]
Comments about programming and debugging
The plain program
#include
#include
#include <ginkgo/ginkgo.hpp>
template
{
const auto trail = span{i + 1, A.length(0)};
A(trail, i) = A(trail, i) / A(i, i);
A(trail, trail) = A(trail, trail) - mmul(A(trail, i), A(i, trail));
}
}
template
{
std::cout << std::setprecision(2) << std::fixed;
std::cout << "L = [";
for (int i = 0; i < A.length(0); ++i) {
std::cout << "\n ";
for (int j = 0; j < A.length(1); ++j) {
std::cout << (i > j ? A(i, j) : (i == j) * 1.) << " ";
}
}
std::cout << "\n]\n\nU = [";
for (int i = 0; i < A.length(0); ++i) {
std::cout << "\n ";
for (int j = 0; j < A.length(1); ++j) {
std::cout << (i <= j ? A(i, j) : 0.) << " ";
}
}
std::cout << "\n]" << std::endl;
}
int main(int argc, char* argv[])
{
using ValueType = double;
using IndexType = int;
ValueType data[] = {
2., 4., 5., -1.0,
4., 11., 12., -1.0,
6., 24., 24., -1.0
};
auto A =
factorize(A);
print_lu(A);
}