Or perhaps this is somehow all my fault.

Someone asked me if I could verify this for them and I'm seeing what they were seeing.

Start Mathematica.

In[1]:= $Version

Out[1]= "9.0 for Microsoft Windows (64-bit) (January 25, 2013)"

(with the task manager running to watch peak memory use}

Mathematica.exe 87,000k

MathKernel.exe 69,656k

Mathkernel.exe 57,468k

Nothing surprising. Evaluate this expression

In[1]:= x1 = I w; x2 = 2 I w;

Integrate[E^(I x t)/((x - x1) (x - x2)), {x, -Infinity, Infinity}]

Out[2]= ConditionalExpression[(1/w)(I Cosh[2 w Abs[t]] CosIntegral[-2 I w Abs[t]] - I Cosh[2 w Abs[t]]

CosIntegral[2 I w Abs[t]] - \[Pi] Cosh[w Abs[t]] Sign[t] + \[Pi] Cosh[2 w Abs[t]] Sign[t] + \[Pi]

Sinh[w Abs[t]] + I CosIntegral[I w Abs[t]] (Cosh[w Abs[t]] - Sign[t] Sinh[w Abs[t]]) + I

CosIntegral[-I w Abs[t]] (-Cosh[w Abs[t]] + Sign[t] Sinh[w Abs[t]]) - \[Pi] Sinh[2 w Abs[t]] -

I CosIntegral[-2 I w Abs[t]] Sign[t] Sinh[2 w Abs[t]] + I CosIntegral[2 I w Abs[t]] Sign[t]

Sinh[2 w Abs[t]]), t \[Element] Reals && Re[w] != 0]

Mathematica.exe 91,432k

MathKernel.exe 137,356k

Mathkernel.exe 57,468k

Nothing surprising. It does that quickly every time I've tried that.

Now add a relevant simple assumption and evaluate.

In[3]:= x1 = I w; x2 = 2 I w;

Integrate[E^(I x t)/((x - x1) (x - x2)), {x, -Infinity, Infinity}, Assumptions -> {t > 0, w > 0}]

Out[4]= -((2 E^(-2 t w) (-1 + E^(t w)) \[Pi])/w)

The result displays quickly, the system appears to be idle and then memory use begins to climb rapidly until

Mathematica.exe 92,240k

MathKernel.exe 3,494,244k

Mathkernel.exe 57,868k

and the system appears to hang, apparently busy consuming all available memory and swap space. All programs are "not responding."

If I don't touch the keyboard for a few minutes or longer sometimes the displays will black out and sometimes return,

sometimes minutes later the memory currently used, as opposed to peak values, will decline back to a few times nominal values

and sometimes the system will again be responsive, but often it seems that the system is still substantially slower than before.

It doesn't seem to necessarily happen every time, but most times this seems to happen and I've tried this dozens of ways.

It does not appear to require Integrate. If neither or only one of the assumptions is used I haen't seen this happen.

Simplify and FullSimplify with both assumptions appears to also be able to reproduce this.

Not realizing what is going on and trying to use the keyboard or mouse to sieze control only appears to compound the problem.

Restarting the machine and restarting Mathematica do not change the behavior.

Has his little example somehow corrupted my Mathematica or my machine?

Or is this all my fault and I've done something to make this happen?

I've never seen particular "unexpected behavior" like this.

I vaguely remember some comment from a few years ago about how having a dual core machine and/or a newer

version of Mathematica would overcome the difficulty with Version 5.2 where a run-away calculation could consume

so many resources that it was difficult or nearly impossible to get control to be able to kill the kernel.

I haven't noticed the ability to do that with Version 9 and an I5-750 processor. Is that some mistake I'm making?

Thank you