GPROF TUTORIAL PDF

This manual describes the GNU profiler, gprof , and how you can use it to determine which parts of a program are taking most of the execution time. We assume that you know how to write, compile, and execute programs. GNU gprof was written by Jay Fenlason. Permission is granted to make and distribute verbatim copies of this manual provided the copyright notice and this permission notice are preserved on all copies. Permission is granted to copy and distribute modified versions of this manual under the conditions for verbatim copying, provided that the entire resulting derived work is distributed under the terms of a permission notice identical to this one. Permission is granted to copy and distribute translations of this manual into another language, under the same conditions as for modified versions.

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As such, our onsite LC Hotline call center is closed. If you need to reach the Hotline, email is the best way to reach them at this time: Technical Consultants: lc-hotline llnl. Monday—Friday 8am—12pm, 1—pm B R Q-clearance area.

Gprof is a performance analysis tool used to profile applications to determine where time is spent during program execution. Gprof works by automatically instrumenting your code during compilation, and then sampling the application's program counter during execution. Sampling data is saved in a file, typically named gmon. Gprof was developed as an extension of the prof command, by providing a call graph of the program's execution. Note that if you compile and link as separate steps in your application build, you will need to include -pg in both steps.

For example:. Run your application as usual. The example below shows a 16 task MPI application running in the pdebug partition on a Linux cluster. View the results: use the gprof command to convert the output file s into a human-readable report.

Several examples are shown below:. Another option for parallel programs is to sum all output files into a single gmon. Gprof's output consists of a human-readable report produced from the binary sampling file s created when the application was executed.

By default the report is written to stdout, which can always be redirected to a file with a name of your choosing. For parallel programs, the report is a summation of the files used to produce it. Gprof's report consists of three sections, each of which is discussed below.

Note that there are a number of options available to customize Gprof's report - see the Gprof Documentation for details. The Flat Profile section shows the total amount of time your program spent executing each function, sorted by decreasing run-time.

Unless the -z option is used, functions with no apparent time spent in them, and no apparent calls to them, are not mentioned. Note that if a function was not compiled for profiling, and didn't run long enough to show up on the program counter histogram, it will be indistinguishable from a function that was never called. An example Flat Profile section is shown below.

Note that the report includes an explanation of what each column means. As discussed in the Quick Start section above, the -pg flag is required when compiling and linking.

For applications where compiling and linking are separate steps, -pg must be included in both steps. It is used to produce a unique sampling data file for each process in a parallel application. See step 2 under the Quick Start section above. Skip to main content.

Search form. Development Environment Software. Related Content. Flat Profile The Flat Profile section shows the total amount of time your program spent executing each function, sorted by decreasing run-time. Flat profile: Each sample counts as 0. This is the major sort for this listing. This is the minor sort for this listing. The index shows the location of the function in the gprof listing.

If the index is in parenthesis it shows where it would appear in the gprof listing if it were to be printed. Call Graph granularity: each sample hit covers 2 byte s for 0. FormatControl [29]. GetMyLocalContext [16]. GetUnit [10]. IOSetRecordOffset [23]. Searching the Web will turn up Gprof tutorials and more.

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As such, our onsite LC Hotline call center is closed. If you need to reach the Hotline, email is the best way to reach them at this time: Technical Consultants: lc-hotline llnl. Monday—Friday 8am—12pm, 1—pm B R Q-clearance area. Gprof is a performance analysis tool used to profile applications to determine where time is spent during program execution. Gprof works by automatically instrumenting your code during compilation, and then sampling the application's program counter during execution. Sampling data is saved in a file, typically named gmon. Gprof was developed as an extension of the prof command, by providing a call graph of the program's execution.

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Through profiling one can determine the parts in program code that are time consuming and need to be re-written. This helps make your program execution faster which is always desired. In very large projects, profiling can save your day by not only determining the parts in your program which are slower in execution than expected but also can help you find many other statistics through which many potential bugs can be spotted and sorted out. The last step above produces an analysis file which is in human readable form. This file contains a couple of tables flat profile and call graph in addition to some other information.

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Gprof calculates the amount of time spent in each routine. Next, these times are propagated along the edges of the call graph. Cycles are discovered, and calls into a cycle are made to share the time of the cycle. Several forms of output are available from the analysis. The flat profile shows how much time your program spent in each function, and how many times that function was called. If you simply want to know which functions burn most of the cycles, it is stated concisely here. The call graph shows, for each function, which functions called it, which other functions it called, and how many times.

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