Simplify bug?
- To: mathgroup at yoda.ncsa.uiuc.edu
- Subject: Simplify bug?
- From: smithw at mathnx.math.byu.edu (Bill Smith)
- Date: Wed, 13 Feb 91 11:30:06 MST
I can't remember whether this sort of bug has been noted before.
The following 4x4 matrix arises in trying to compute eigenvectors
for a certain matrix.
Mathematica (MIPS) 1.2 (November 8, 1989) [With pre-loaded data]
by S. Wolfram, D. Grayson, R. Maeder, H. Cejtin,
S. Omohundro, D. Ballman and J. Keiper
with I. Rivin and D. Withoff
Copyright 1988,1989 Wolfram Research Inc.
-- Terminal graphics initialized --
In[1]:= {{(2 - 5*z + 4*z^2 - z^3)/
(2*a - b - 2*z - 5*a*z + 2*b*z + 5*z^2 + 4*a*z^2 -
b*z^2 - 4*z^3 - a*z^3 + z^4),
(-b + 2*b*z - b*z^2)/
(2*a - b - 2*z - 5*a*z + 2*b*z + 5*z^2 + 4*a*z^2 -
b*z^2 - 4*z^3 - a*z^3 + z^4),
(3*b - 2*c - 3*b*z + 3*c*z - c*z^2)/
(2*a - b - 2*z - 5*a*z + 2*b*z + 5*z^2 + 4*a*z^2 -
b*z^2 - 4*z^3 - a*z^3 + z^4), 0},
{(-1 + 2*z - z^2)/
(2*a - b - 2*z - 5*a*z + 2*b*z + 5*z^2 + 4*a*z^2 -
b*z^2 - 4*z^3 - a*z^3 + z^4),
(a - z - 2*a*z + 2*z^2 + a*z^2 - z^3)/
(2*a - b - 2*z - 5*a*z + 2*b*z + 5*z^2 + 4*a*z^2 -
b*z^2 - 4*z^3 - a*z^3 + z^4),
(-3*a + c + 3*z + 3*a*z - c*z - 3*z^2)/
(2*a - b - 2*z - 5*a*z + 2*b*z + 5*z^2 + 4*a*z^2 -
b*z^2 - 4*z^3 - a*z^3 + z^4), 0},
{0, 0, (2*a - b - 2*z - 3*a*z + b*z + 3*z^2 + a*z^2 -
z^3)/(2*a - b - 2*z - 5*a*z + 2*b*z + 5*z^2 +
4*a*z^2 - b*z^2 - 4*z^3 - a*z^3 + z^4), 0},
{0, 0, 0, (2*a - b - 2*z - 3*a*z + b*z + 3*z^2 + a*z^2 -
z^3)/(2*a - b - 2*z - 5*a*z + 2*b*z + 5*z^2 +
4*a*z^2 - b*z^2 - 4*z^3 - a*z^3 + z^4)}}
In[2]:= Simplify[%]
GCD::ptoomany: Tried 4792 primes, algorithm failed.
Error: iPsparseGcdcf interpolation error
Process abort
This is on a MIPS RS2030.
The same thing happens on a NeXTcube (68040):
GCD::ptoomany: Tried 4792 primes, algorithm failed.
BTW, Factor works just fine here to give:
{{-((-2 + z)/(2*a - b - 2*z - a*z + z^2)),
-(b/(2*a - b - 2*z - a*z + z^2)),
-((3*b - 2*c + c*z)/
((-1 + z)*(2*a - b - 2*z - a*z + z^2))), 0},
{-(2*a - b - 2*z - a*z + z^2)^(-1),
-((-a + z)/(2*a - b - 2*z - a*z + z^2)),
-((-3*a + c + 3*z)/
((-1 + z)*(2*a - b - 2*z - a*z + z^2))), 0},
{0, 0, -(-1 + z)^(-1), 0}, {0, 0, 0, -(-1 + z)^(-1)}}