Total seconds counts are wrong.

AdamMil

My previous post on this seems to have been ignored, so I'm posting again.

I ran the mandelbrot program for about 10 seconds, and the results said Main() (with children) took 262 seconds.

I tried running the application and immediately closing it. Although it ran for less than a second, it said Main() (with children) took over 40 seconds.

What's going on here?

Brian Donahue

Hi Adam,

I've asked Tom to reply to the previous topic again. This is frankly a bit above my head.

AdamMil

He can just reply here.

I've split my previous topic into two different topics.

I think that was part of the problem before. One half of my topic was addressed and the other half was not addressed at all.

So to make things more clear, both for you guys and for potential readers, I've split it into two topics.

Tom Harris

Hi Adam,

I don't know what is going wrong for you here. We use the mandelbrot sample for all our platform testing and have not run into your scenario. Does the same thing happen to you with the simplest windows forms app on your machine (i.e just an empty form). Does it happen everytime with the mandelbrot sample.

Thanks,

Tom

Red Gate Software Ltd.

AdamMil

Yes, it happens every time I run the mandelbrot sample. It's always way off, but not always by the same amount. If I run the application for five seconds, sometimes it'll say 30 seconds and sometimes it'll say 300 seconds.

It also happens when I use a blank windows forms app.

I'll post a screenshot of this when I get home.

AdamMil

Here's the screenshot.

Neil Davidson

Adam,

Can you let me know what hardware you're running it on please (type of processor, number of processors, clock speed, O/S, whether it's a virtual machine etc.)

- Neil

AdamMil

OS: Microsoft Windows XP Professional 5.1.2600 SP2 Build 2600
System: HP Pavilion dv4000 (PC253AV)
CPU: 1x 1.5ghz Intel M processor (single core)
RAM: 512MB

Installed .NET Framework versions:
2.0.50727.42
1.1.4322

More information available here (System Info file, right-click and save somewhere):
http://www.adammil.net/adam-laptop.nfo

AdamMil

This is just a wild guess on my part, but here it is:

Do you guys use the RDTSC x86 instruction to retrieve the "time"?

That's not reliable. For one thing, it's not likely to work properly on machines with multiple CPUs because because whenever a thread switches CPUs, your timings will probably get screwed up. They may even become negative.

Second, modern laptop CPUs can alter their clock rate. For instance, during periods of low CPU usage, my laptop's clock rate may be only 33 mhz or something. This is of course done to save power.

With a variable clock-rate CPU, you obviously can't rely on RDTSC to provide wall-clock timing.

Just a guess,
-- Adam

Tom Harris

Hi,

you are correct - we are using the rdtsc instruction to measure the wall time.

Sorry that this does not work correctly on your lap top.

Thanks for pointing this out. We will address the problem in the next version of ANTS Profiler.

Tom Harris

Red Gate Software Ltd