Why is eValid maximum sync rate only 100 Hertz (Hz)

Applying eValid to AJAX applications that require advanced DOM-based methods.

Why is eValid maximum sync rate only 100 Hertz (Hz)

Postby TanyaS » Tue Mar 31, 2015 10:40 am

Hi,

I've been looking at eValid during my trial/evaluation.

Why is your maximum sync rate only 100 Hz?

Can eValid have a higher hertz rate?

Thanks
TanyaS
 
Posts: 1
Joined: Tue Mar 31, 2015 10:35 am

Re: Why is eValid maximum sync rate only 100 Hertz (Hz)

Postby eValid » Wed Apr 01, 2015 2:56 pm

TanyaS wrote:Hi,

I've been looking at eValid during my trial/evaluation.

Why is your maximum sync rate only 100 Hz?

Can eValid have a higher hertz rate?

Thanks


Thanks for asking TanyaS.

Fair enough question.

Why would you want more?

That rate gives you 0.01 second resolution.

Here, for your refernce, is the manual page for the window where you can select the synchronization retry interval:

http://www.e-valid.com/Products/Documen ... ation.html

But the story is a bit more complex. It turns out that if you increase the rate at which you check the DOM for a particular value too often then you interfere with the operation of the playback engine.

Slowing down the playback engine too much is as bad as having less precise measurements of time intervals.

We determined the maximum synchronization rate some time ago by experimentation.

Using a pre-release eValid build we varied the interval in decreasing amounts until we saw a significant decrease in response time in the playback engine.

After we got above 100 Hz (which is the 0.01 second = 10 msec maximum interval that is in the product) we observed an exponentially increasing level of overhead, relative to the ordinary playback engine overhead.

We searched for the "sweet spot," that is, when the fraction of the machine resource that was performing synchronization was about 50% of the resource that was supervising playback.

It was close to 5 msec on a slow PC, so to err on the side of caution we chose 10 msec as the shortest synchronization interval.

For faster machines, at 10 msec you still get 10 msec time resolution and you don't have to worry about having perturbed the reality of your test. This seems to be a good compromise.

-- evalid Support
eValid
 
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