       Re: MathKernel crashes

• To: mathgroup at smc.vnet.net
• Subject: [mg72819] Re: MathKernel crashes
• From: Jean-Marc Gulliet <jeanmarc.gulliet at gmail.com>
• Date: Sun, 21 Jan 2007 05:25:22 -0500 (EST)
• Organization: The Open University, Milton Keynes, UK
• References: <eosgop\$9ai\$1@smc.vnet.net>

```nandan wrote:
> Hallo:
>
> MathKernel crashes, since I use recursive function for calculation. I
> have 2 of the important functions for my calculation as given below:
> \$RecursionLimit=Infinity;
>
> pi[0, \[Theta]_] := 0;
> pi[1, \[Theta]_] := 1;
> pi[i_, \[Theta]_]\  := pi[i, \[Theta]]  = ((2  i - 1)/(i - 1))
-------------------^
Extra backslash must be removed

> Cos[\[Theta]] pi[i - 1, \[Theta]] - (i/(i - 1)) pi[i - 2,\[Theta]]);
--------------------------------------------------------------------^
Extra parentheses must be removed

> \[Tau][i_, \[Theta]_] := \[Tau][i, \[Theta]] = i Cos[\[Theta]] pi[i,
> \[Theta]] - (i + 1)pi[i - 1, \[Theta]];

Here is a corrected version of the code:

In:=
pi[0, Î¸_] = 0;
pi[1, Î¸_] = 1;
pi[i_, Î¸_] := pi[i, Î¸] =
((2*i - 1)/(i - 1))*Cos[Î¸]*pi[i - 1, Î¸] -
(i/(i - 1))*pi[i - 2, Î¸];
Ï?[i_, Î¸_] := Ï?[i, Î¸] = i*Cos[Î¸]*pi[i, Î¸] -
(i + 1)*pi[i - 1, Î¸];

In:=
pi[14, Pi/3]

Out=
30439185
--------
8388608

> In this case, I can get solution to any numerical value like pi[14,
> \[Pi]/3]. But quite a few times, it happened that MathKernel quitted,I

It would have been nice that you provided an example of such a call.

> started again, but it started another processor parallel to that. Later

Not sure to understand what you mean: if the kernel really quits, you
have no more kernel process loaded into memory.

> I wanted to calculate another function as follows:
> S1Temp[i_, \[Theta]_] := ((2 l + 1)/(l (l + 1))) (an[l] pi[l, \[Theta]]
---------^
Inconsistent syntax: i is never used in the code: do you mean l? At any
rate, this definition will cause an infinite recursion whenever it is
called. Increasing \$RecursionLimit will do nothing.

>  + bn[l]  \[Tau][l, \[Theta]]);
>
> But in this case, whenever I try to calculate S1Temp[14, \[Pi]/3], it
> simply quits and, sometimes crashes. I have to always restart
> Mathematica to start over again.

Here is a corrected version of the code:

In:=
S1Temp[l_, Î¸_] := ((2*l + 1)/(l*(l + 1)))*
(an[l]*pi[l, Î¸] + bn[l]*Ï?[l, Î¸]);

In:=
S1Temp[14, Pi/3]

Out=
29   30439185 an   115937115 bn
--- (--------------- - ----------------)
210      8388608           8388608

Now, the above result might or might not be what you expected since you
did not provide any definition for an[i] and bn[i]. (Are they functions
or arrays of values?)

Regards,
Jean-Marc

```

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