75 lines
1.6 KiB
PHP
75 lines
1.6 KiB
PHP
function swap_rows(&$a, &$b, $r1, $r2)
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{
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if ($r1 == $r2) return;
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$tmp = $a[$r1];
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$a[$r1] = $a[$r2];
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$a[$r2] = $tmp;
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$tmp = $b[$r1];
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$b[$r1] = $b[$r2];
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$b[$r2] = $tmp;
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}
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function gauss_eliminate($A, $b, $N)
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{
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for ($col = 0; $col < $N; $col++)
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{
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$j = $col;
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$max = $A[$j][$j];
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for ($i = $col + 1; $i < $N; $i++)
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{
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$tmp = abs($A[$i][$col]);
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if ($tmp > $max)
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{
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$j = $i;
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$max = $tmp;
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}
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}
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swap_rows($A, $b, $col, $j);
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for ($i = $col + 1; $i < $N; $i++)
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{
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$tmp = $A[$i][$col] / $A[$col][$col];
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for ($j = $col + 1; $j < $N; $j++)
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{
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$A[$i][$j] -= $tmp * $A[$col][$j];
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}
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$A[$i][$col] = 0;
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$b[$i] -= $tmp * $b[$col];
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}
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}
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$x = array();
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for ($col = $N - 1; $col >= 0; $col--)
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{
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$tmp = $b[$col];
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for ($j = $N - 1; $j > $col; $j--)
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{
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$tmp -= $x[$j] * $A[$col][$j];
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}
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$x[$col] = $tmp / $A[$col][$col];
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}
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return $x;
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}
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function test_gauss()
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{
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$a = array(
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array(1.00, 0.00, 0.00, 0.00, 0.00, 0.00),
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array(1.00, 0.63, 0.39, 0.25, 0.16, 0.10),
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array(1.00, 1.26, 1.58, 1.98, 2.49, 3.13),
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array(1.00, 1.88, 3.55, 6.70, 12.62, 23.80),
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array(1.00, 2.51, 6.32, 15.88, 39.90, 100.28),
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array(1.00, 3.14, 9.87, 31.01, 97.41, 306.02)
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);
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$b = array( -0.01, 0.61, 0.91, 0.99, 0.60, 0.02 );
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$x = gauss_eliminate($a, $b, 6);
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ksort($x);
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print_r($x);
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}
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test_gauss();
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