[Contents] [Chapter 3] [Chapter 5] [Index]

Profiling and Tracing

This chapter provides a description of profiling and how to produce a log of calls to MPI routines and then view the log. It also provides a description of tracing and how to trace MPI calls. The chapter consists of the following sections:

• Introducing Profiling
• Introducing Tracing

4.1 Introducing Profiling

Compaq MPI includes modified versions of the profiling library and Upshot viewer that come with the MPICH kit. You can use the profiling library to produce a log of calls to Compaq MPI routines. This records the start and end time of each call and other message information. You can then use Upshot to view, search, and scroll the log.

4.1.1 Differences between Compaq MPI and MPICH Profiling Libraries

The Compaq MPI profiling library differs from the MPICH profiling library in the following ways:

• Library code is modified to eliminate many of the unaligned access warnings on Alpha systems
• Time resolution is improved from approximately 1 millisecond to approximately 1 microsecond
• The Compaq MPI profiling library works with the MPI Fortran API
• Message sent/received events are generated for MPI_Waitall, MPI_Waitany, MPI_Waitsome, MPI_Testall, MPI_Testany and MPI_Testsome

4.1.2 Differences between Compaq MPI and MPICH Upshot

The Compaq MPI version of Upshot differs from the MPICH version in the following ways:

• Loading of log files speeded up
• New zoom controls added
• Search capability added
• Added popup window with event, state, and message details
• Added links from non-blocking events to the wait, test, or cancel that terminates the request

4.1.3 Logging Calls to Compaq MPI Routines

To use the profiling libraries to log calls, follow these steps:

1. Compile your code in the normal way.

2. Link to the profiling libraries instead of the normal MPI library.

   For example, for C programs, enter:
   

   cc -o myprog.log myprog.c -llmpi -lpmpi -lmpi -lrt -pthread

   For example, for Fortran programs, enter:
   

   f77 -o myprog.log myprog.f -lfmpi -llmpi -lpmpi -lmpi -lrt -pthread

3. Run the program and it produces a log file called executablename_profile.log, where executablename is the name of the program.

4.1.4 Viewing the Log using Upshot

To use the Compaq MPI version of Upshot, follow these steps:

1. To start Upshot, enter the following command:
   

   upshot

   A window appears with an entry field, and Select Logfile, Setup, Options and Quit buttons.

2. Enter the full name of the log file or use the Select Logfile button to select the log file name from the file browser window.

   For example,
   

   /usr/examples/mpi/ping_mpi_profile.log

3. Click on the Setup button.

   A small window appears while the file is loading. When the file is loaded, the timeline window is displayed.

   The features of this window and the actions you can perform are described here:

   • There are a number of buttons at the top of the timeline window:

     1. Horizontal Zoom In/Out: Zooms in or out to display more or less detailed information. Instead of using the Horizontal Zoom In button, you can select the region you want to see by using MB3 on a timeline or on either of the two scales at the bottom of the window. When you click MB3 on a timeline, a yellow vertical line appears at that point. This is used as the zoom point for the zoom buttons. You will notice that a red line appears as you move the mouse. This indicates the area you wish to zoom in on.
     2. Vertical Zoom In/Out: Zooms in or out to display more or less detailed information.
     3. Detailed Zoom: allows you to define the time for the process you wish to view and the factor for displaying it.
     4. Reset: restores the window to the state it was in when the log was loaded.
     5. Print: prints the contents of the window to file.
     6. Find: opens a window where you can search for events. You can search for specific event types in specific timelines, or you can search for the next or previous event of any type as a handy scrolling mechanism.
     7. Close: closes the timeline window.

   • The timeline window shows one line per process (numbered vertically), with events and states on each line.

   • The routines used by the program are placed beneath the buttons at the top of the window and above the processes. Clicking on a routine causes a window to appear that displays a histogram of state durations for the routine.

   • The black arrow indicates a message sent from the process at the tail of the arrow to the process at the head of the arrow. You can press MB1 when the cursor is over the arrow to display details about that message, for example, message size, source, destination ranks.

   • The yellow arrows indicate the duration of non-blocking requests. Non-blocking MPI communications use `requests' that are typically initiated by a non-blocking send or receive, such as MPI_Isend or MPI_Irecv, and are usually terminated by a wait or test call.

   Messages sent or received this way are logged as though they are sent or received by the terminating wait or test call. Yellow arrows on a timeline indicate the start and end of a request and go from the send or receive call that initiated the request to the test, wait, or cancel call that ends the request.

   • You can scroll the timeline area using the scroll bars or by moving the mouse cursor over the timeline while holding down MB2.

   4.2 Introducing Tracing

   You can use the tracing library to output to the standard output, information describing each of the MPI calls executed in the program.

   The information consists of:

   • a trace line containing the rank in MPI_COMM_WORLD of the calling process
   • a trace line indicating the call has completed

   Most send and receive routines indicate the value of count, tag, and partner (destination for send, source for receives).

   4.2.1 Tracing MPI Calls

   To use the tracing library to print trace lines for MPI calls, follow these steps:

   1. Compile your code in the normal way.

   2. Link to the tracing library instead of the normal MPI library.

      For example, for C programs, enter:
      

      cc -04 -o myprog.log myprog.c -ltmpi -lpmpi -lmpi -pthread -lrt

      For example, for Fortran programs, enter:
      

      f77 -o myprog.log myprog.f -lfmpi -ltmpi -lpmpi -lmpi -pthread -lrt

   3. Run the program and the trace lines are produced.

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