Computation ceases, and notebook inactive

*To*: mathgroup at smc.vnet.net*Subject*: [mg112171] Computation ceases, and notebook inactive*From*: Arielpk <arielpk2 at gmail.com>*Date*: Fri, 3 Sep 2010 06:09:18 -0400 (EDT)

Shalom, I am trying to solve a differential problem. The general details are: a. It is a fourth order equation; b. It has the structure: u''''[x] + p[x]*u''[x] + p'[x]*u'[x] + q[x]*u[x] == u[x]. The p[x] and q[x] can be various ones. Now the problem: For simple choices of p[x] and q[x] (say, having some of them to be always zero or some other constant) gives an analytic solution. For other choices, it is reasonable to expect to have no analytical solution, so NDSolve will be necessary. So what bothers me? Suppose I choose p[x]=Sin[x], and the system cannot find a solution with DSolve. I would like to: a. Obtain a message saying that the DSolve cannot find a solution, preferrably obtain a return code that means the same. b. Being able to keep working with the session. What actually happens is none of these: a. No message; no error code; the computation seems to be stuck. b. Going back to these p[x] and q[x], and defining something simpler for them, such that no problems are expected, does not help. regards, Amir