LU decomposition: Difference between revisions

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#2A((1 0 0 0) (0 0 1 0) (0 1 0 0) (0 0 0 1))</lang>

=={{header|D}}==

⚫

Using some functions from Matrix multiplication task.

<lang d>import std.stdio, std.algorithm, std.typecons;

⚫

// ~~plus~~ functions from Matrix multiplication task

/// Creates a nxn identity matrix.

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return m;

}

/// Swap two rows l and k of a 2D array matrix m.

pure void swapRows(T)(ref T[][] m, const int l, const int k) {

swap(m[l], m[k]);

}

/// Creates the pivoting matrix for m.

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T max = m[j][j];

int row = j;

foreach (i; j .. n) {

foreach (i; j .. n)

if (m[i][j] > max) {

max = m[i][j];

row = i;

}

if (j != row)

~~swapRows~~(P, j, row);

swap(P[j], P[row]);

}

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s1 += U[k][j] * L[i][k];

U[i][j] = A2[i][j] - s1;

}

foreach (i; j .. n) {

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return tuple(L, U, P);

}

void main() {

enum double[][] a = [[1, 3, 5], [2, 4, 7], [1, 1, 0]];

~~auto~~ ~~lua =~~ lu(a);

foreach (part; lu(a).tupleof)

writeln(prettyPrint(~~lua[0]~~), "\n\n",

writeln(prettyPrint(part), "\n");

writeln();

prettyPrint(lua[1]), "\n\n",

prettyPrint(lua[2]), "\n\n");

enum double[][] b = [[11, 9, 24, 2], [1, 5, 2, 6],

[3, 17, 18, 1], [2, 5, 7, 1]];

~~auto~~ ~~lub =~~ lu(b);

foreach (part; lu(b).tupleof)

writeln(prettyPrint(~~lub[0]~~), "\n\n",

writeln(prettyPrint(part), "\n");

prettyPrint(lub[1]), "\n\n",

prettyPrint(lub[2]));

}</lang>

Output: