View Comparison Data

Intel® VTune™ Amplifier compares analysis results and displays difference in a separate result tab <result1>-<result2> in the following windows:

  • Summary window provides top-level difference for the analysis run.

  • Bottom-up window displays difference for functions and their callers per metric.

  • Top-down Tree window displays difference for functions and their callees per metric.

  • Caller/Callee window displays difference for a selected function, their callers and callees per metric.

Comparing Recompiled Binary Files

By default, the VTune Amplifier displays compared functions grouped by the Call Stack granularity, which is based on function instances. But you may want to switch to the Source Function Stack grouping to get more accurate comparison results in the following cases:

  • You slightly changed the source and recompiled the code.

  • You changed compilation options and recompiled the code.

  • You are comparing results compiled and collected for different Intel microarchitectures

For example, your binary with a my_f function was modified with adding a new function my_f1 and new calls of this function. As a result, my_f address has changed. If you compare the results before and after the modification using the default Call Stack grouping, the VTune Amplifier treats the same functions with different addresses as separate instances and does not compare them:

When the data is aggregated by Source Function Stack, the VTune Amplifier ignores start addresses and compares functions by source file objects:

Bar Data Respresentation

If you chose the Bar format to display the performance data in the Bottom-up or Top-down Tree window, the VTune Amplifier calculates the bar size as follows:

Result Data Column

Difference Column

cell_data_value/absolute_max_value_in_result_column

cell_data_value/max(absolute_max_value_in__1st_result_column, absolute_max_value_in_corresponding_2nd_result_column)

Example: Calculation of the Bar Size

The table below provides an example on how the VTune Amplifier calculates the bar size in the compare mode based on the absolute max CPU time value and performance data per column:

 

CPU Time:r001

CPU Time:r002

CPU Time:Difference

Absolute max value (calculated by the VTune Amplifier internally but not exposed in the grid)

10s

20s

20s

Performance data

1s

3s

2s

Bar size

1s/max(10s,20s)

3s/max(10s,20s)

2s/max(10s,20s)

For more complete information about compiler optimizations, see our Optimization Notice.
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