The data collected during one execution of your application is called an experiment. The experiment consists of a set of files that are stored in a directory. The name of the experiment is the name of the directory.
In addition to recording the experiment data, the Collector creates its own archives of the load objects used by the program. These archives contain the addresses, sizes, and names of each object file and each function in the load object, as well as the address of the load object and a timestamp for its last modification. Archives might also have copies of all shared objects and some or all of the source files. See er_archive Utility for more information.
Experiments are stored by default in the current directory. If this directory is on a networked file system, storing the data takes longer than on a local file system and can distort the performance data. You should always try to record experiments on a local file system if possible. You can specify the storage location when you run the Collector.
Experiments for descendant processes are stored inside the experiment for the founder process.
The default name for a new experiment is test.1.er . The suffix .er is mandatory: if you provide a name without this suffix, an error message is displayed and the name is not accepted.
If you choose a name with the format experiment.n.er, where n is a positive integer, the Collector automatically increments n by one in the names of subsequent experiments. For example, mytest.1.er is followed by mytest.2.er, mytest.3.er , and so on. The Collector also increments n if the experiment already exists, and continues to increment n until it finds an experiment name that is not in use. If the experiment name does not contain n and the experiment exists, the Collector prints an error message.
Subexperiments follow similar naming rules. See Subexperiments for more information.
Experiments can be collected into groups. The group is defined in an experiment group file, which is stored by default in the current directory. The experiment group file is a plain text file with a special header line and an experiment name on each subsequent line. The default name for an experiment group file is test.erg. If the name does not end in .erg, an error is displayed and the name is not accepted. Once you have created an experiment group, any experiments you run with that group name are added to the group.
To manually create an experiment group file, create a plain text file whose first line is as follows:
#analyzer experiment group
Then add the names of the experiments on subsequent lines. The file extension must be.erg.
You can also create an experiment group by using the –g argument to the collect command.
Experiments for descendant processes are named with their lineage as follows. To form the experiment name for a descendant process, an underscore, a code letter, and a number are added to the stem of its creator’s experiment name. The code letter is f for a fork, x for an exec, and c for combination. The number is the index of the fork or exec (whether successful or not). For example, if the experiment name for the founder process is test.1.er, the experiment for the child process created by the third call to fork is test.1.er/_f3.er . If that child process calls exec successfully, the experiment name for the new descendant process is test.1.er/_f3_x1.er.
Data for MPI programs are collected by default into test.1.er, and all the data from the MPI processes are collected into subexperiments, one per rank. The Collector uses the MPI rank to construct a subexperiment name with the form M_rm.er, where m is the MPI rank. For example, MPI rank 1 would have its experiment data recorded in the test.1.er/M_r1.er directory.
Experiments on the kernel by default are named ktest.1.er rather than test.1.er. When data is also collected on user processes, the kernel experiment contains subexperiments for each user process being followed.
The subexperiments are named using the format _process-name_PID_process-id.1.er. For example an experiment run on a sshd process running under process ID 1264 would be named ktest.1.er/_sshd_PID_1264.1.er.
If you want to move an experiment to another computer to analyze it, you should be aware of the dependencies of the analysis on the operating environment in which the experiment was recorded.
The experiment contains all the information necessary to compute metrics at the function level and to display the timeline. However, if you want to see annotated source code or annotated disassembly code, you must have access to versions of the load objects or source files that are identical to the ones used to build the target or the experiment.
See How the Tools Find Source Code for a description of the process used to find an experiment's source code.
To ensure that you see the correct annotated source code and annotated disassembly code for your program, you can copy the source code, the object files, and the executable into the experiment using the er_archive command before you move or copy the experiment.
See the er_archive(1) man page for more information.