Marking Samples

The Sampling Collector interrupts data gathering to end one sample and begin another at these three points:

• At breakpoints

• When you choose Collect New Sample

• Periodically, at intervals you set with the slider

Breakpoints

Because data is always summarized at breakpoints in the code, you can set breakpoints at any location at which you want to summarize collected data.

• If your application is compiled using the -g option, you can set breakpoints in those specific areas of the code pertaining to the information you want to collect. The breakpoints can be set at the beginning or end of a function, or on any line of code.

• If the application is compiled with the -O option, you can set breakpoints on functions, but not on specific source-code lines.

New Sample Command

If you select the radio button labeled "Manually, on `New Sample' command", you can use the New Sample command on the Collect menu to check data at whatever points in the application you wish without setting a breakpoint in the code. This is useful if you are interested in measuring human interaction with the application--for example, the time it takes to choose a command from a menu or to type in a keyboard command.

Periodic Sampling

If you select the radio button labeled "Periodically", the Sampling Collector takes behavior data samples as you observe the running application, to give you a uniform view of the application's behavior. Use the Period slider at the bottom of the Sampling Collector window to define the intervals at which the Sampling Collector summarizes samples. The interval can be from 1 to 60 seconds.