From bug-octave-request at bevo dot che dot wisc dot edu  Thu Jun  7 13:27:52 2001
Subject: Rcond=NAN in DET
From: "Jianming" <caijianming at yahoo dot co dot uk>
To: <bug-octave at bevo dot che dot wisc dot edu>
Date: Thu, 7 Jun 2001 13:27:44 -0500


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Hi,
   =20

The following expression will cause octave 2.1.34 + atlas 3.2.1 to hang:

C=3D[1,  1.30007902878166e-112, 1,      1;

   9.2176458517918e-188, 1,   9.21764597429266e-188, =
9.21764617989136e-188;

   1,  1.30007903363547e-112, 1,       1;

   1,  1.30007904184461e-112, 1,       1];



[d r] =3D det(C);



This is because the DEGCO returns rcond =3D NaN, but was not tested by =
dMatrix.cc. The method determinant thus proceed to perform DGEDI, which =
will hang.

Attached is a patch which simply add the test condition xisnan(rcond).



Regards,

Jianming






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--- octave-2.1.34.old/liboctave/dMatrix.cc	Sat Apr 21 08:51:22 2001=0A=
+++ octave-2.1.34/liboctave/dMatrix.cc	Tue Jun  5 17:21:55 2001=0A=
 at @ -899,7 +899,7 @@ Matrix::determinant (int& info, double& =0A=
 	{=0A=
 	  volatile double rcond_plus_one =3D rcond + 1.0;=0A=
 =0A=
-	  if (rcond_plus_one =3D=3D 1.0)=0A=
+	  if (rcond_plus_one =3D=3D 1.0 || xisnan(rcond))=0A=
 	    {=0A=
 	      info =3D -1;=0A=
 	      retval =3D DET ();=0A=

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