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D.3.2.16 pos_def
Procedure from library linalg.lib (see linalg_lib).
- Usage:
- pos_def(A); A = constant, symmetric square matrix
- Return:
- int:
1 if A is positive definit ,
0 if not,
-1 if unknown
Example:
| LIB "linalg.lib";
ring r = 0,(x),dp;
matrix A[5][5] = 20, 4, 0, -9, 8,
4, 12, -6, -4, 9,
0, -6, -2, -9, -8,
-9, -4, -9, -20, 10,
8, 9, -8, 10, 10;
pos_def(A);
==> 0
matrix B[3][3] = 3, 2, 0,
2, 12, 4,
0, 4, 2;
pos_def(B);
==> 1
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