What qxdiff annotations mean

Each line in the qxdiff report lists a function whose time has changed. The annotations on each line mean the following:

Symbol

Meaning

   -

Called in the baseline run only

   !

Called in both runs; timing changed

   +

Called in the changed run only

Unless you change the calling structure of the program, qxdiff reports only the functions whose performance has changed (lines marked “!”). You can use the -l option to print a description of the columns and annotations in the qxdiff report.

The qxdiff report summarizes the total number of differences, the change in the total function time count, and the overall percentage change between the baseline and the changed run. The qxdiff script prints the report to stdout.

By default, qxdiff reports changes in operating system call times. These changes can be caused by a different number of calls or changed network traffic loads. You can use the -i option to tell qxdiff to ignore functions that make system calls in order to focus on the changes in compute-bound functions only.

The example on the following page shows the effect of the -i option.

For example, you can use qxdiff -i to see the effect of a different compiler optimization level on the improved_testHash program.

 

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