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=GNU Profiler (gprof) = <!--T:1--> | =GNU Profiler (gprof) = <!--T:1--> | ||
== What is gprof? == | == What is gprof? == | ||
[https://sourceware.org/binutils/docs/gprof/ gprof] is a profiling software which collects information and statistics on your code. Generally, it searches for functions and subroutines in your program and | [https://sourceware.org/binutils/docs/gprof/ gprof] is a profiling software which collects information and compiles statistics on your code. Generally, it searches for functions and subroutines in your program and inserts timing instructions for each one. Executing such a modified program creates a raw data file which can be interpreted by gprof and turned into profiling statistics. | ||
<!--T:2--> | <!--T:2--> | ||
[https://sourceware.org/binutils/docs/gprof/ gprof] | [https://sourceware.org/binutils/docs/gprof/ gprof] comes with the GNU compiler suite and is available with the <tt>gcc</tt> module on our clusters. | ||
== Preparing your application == <!--T:3--> | == Preparing your application == <!--T:3--> | ||
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=== Compiling your code === <!--T:4--> | === Compiling your code === <!--T:4--> | ||
To get useful information from [https://sourceware.org/binutils/docs/gprof/ gprof] , you first need to compile your code with debugging information enabled. With the GNU compilers, you do so by adding the <tt>-pg</tt> option | To get useful information from [https://sourceware.org/binutils/docs/gprof/ gprof], you first need to compile your code with debugging information enabled. With the GNU compilers, you do so by adding the <tt>-pg</tt> option to the compilation command. This option tells the compiler to generate extra code to write profile information suitable for the analysis. Without this option, no call-graph data will be gathered and you may get the following error: | ||
<pre> | <pre> | ||
gprof: gmon.out file is missing call-graph data | gprof: gmon.out file is missing call-graph data | ||
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Once your code has been compiled with the proper options, you then execute it: | Once your code has been compiled with the proper options, you then execute it: | ||
{{Command|/path/to/your/executable arg1 arg2}} | {{Command|/path/to/your/executable arg1 arg2}} | ||
You should run your code the same way as you would | You should run your code the same way as you would without gprof profiling; the execution line does not change. | ||
Once the binary has been executed and finished without any errors, a new file <tt>gmon.out</tt> is created in the current working directory. Note that if your code changes the current directory, <tt>gmon.out</tt> will be created in the new working directory, insofar as your program has sufficient permissions | Once the binary has been executed and finished without any errors, a new file <tt>gmon.out</tt> is created in the current working directory. Note that if your code changes the current directory, <tt>gmon.out</tt> will be created in the new working directory, insofar as your program has sufficient permissions to do so. | ||
=== Getting the profiling data === <!--T:5--> | === Getting the profiling data === <!--T:5--> | ||