Re: Kernel crash using Z transform, version 7, windows

• To: mathgroup at smc.vnet.net
• Subject: [mg109318] Re: Kernel crash using Z transform, version 7, windows
• From: Bob Hanlon <hanlonr at cox.net>
• Date: Wed, 21 Apr 2010 07:47:42 -0400 (EDT)

```I get the same crash; however, if I both Rationalize AND Simplify (but NOT FullSimplify) first, then

\$Version

7.0 for Mac OS X x86 (64-bit) (February 19, 2009)

expr = 0.20056791381984598*I*
E^((-2.3120000000000003 -
2.4929211780559766*I)*n) -
0.20056791381984598*I*
E^((-2.3120000000000003 +
2.4929211780559766*I)*n);

expr2 = Rationalize[expr, 0] // Simplify;

ZTransform[expr2, n, z, Method -> "Holonomic"] //
Simplify // N // Chop

-((0.00019498218407440176*I*
(123.12233073821176*I*z^2 +
19.439038443105282*I*z +
1.2082565103472076*I))/
(z*(0.04455426509374547 + z^2 +
0.00009630406771703447/z^2 +
0.31576787616922936*z +
0.0030987765570423247/z)))

Bob Hanlon

---- "Nasser M. Abbasi" <nma at 12000.org> wrote:

=============
Warning, do not run this before saving your work:

In[1]:= ClearAll["Global`*"];

expr = 0.20056791381984598*I*E^((-2.3120000000000003 -
2.4929211780559766*I)*n) -
0.20056791381984598*I*E^((-2.3120000000000003 + 2.4929211780559766*I)*n);

ZTransform[expr, n, z, Method -> "Holonomic"]

*kernel crash*

But when I do

ZTransform[expr, n, z]

I was getting errors General::lrgexp, but no crash.

The above is an expression generated internally from a program I am working
on, depending on the input parameters, sometimes I get these errors and
sometimes I do not, since the expr will be different each time depending on
the parameters that are entered.

So I was trying to find where the error was coming from. I do not really
understand why this error message is coming. Must be something internal to
Ztransform.

I will send a bug report to WRI support also.

--Nasser

--

Bob Hanlon

```

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