On 10/26/2012 06:35 PM, LUIS BERLIOZ wrote:
det FUNCTION IS HAVING A VERY ANNOYING BEHAVIOR,GIVEN THE ATTACHED MATRIX FOR
EXAMPLE
IF I TRY TO GET THE DETERMINANTS WITH TWO DIFFERENT METHODS:
sage: M=load(PATHTOFILE +'/M.sobj')
sage: M.det()
6.49037107316853e32
sage: from numpy import linalg
sage: linalg.det(M)
-1.5055380070396349e-05
THE SECOND RESULT IS CORRECT (THE MATRIX IS SINGULAR).
THE DEFAULT det FUNCTION SEEMS TO OVERFLOW WITh A MATRIX OF JUST 20 ROWS? IS
THIS A BUG?
Maybe it is a precision problem? Changing the field seems to work:
sage: M = load('./M.sobj')
sage: A = M.change_ring(RealField(100)); A.det()
0.00000000000000000000000000000
sage: A = M.change_ring(RDF); A.det()
-2.51671904975e-05
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