Product specifications
Table Of Contents
- Table of Contents
- 1 Introduction
- 2 Feature Overview
- 3 Step-by-Step Cluster Setup and MPI Usage Checklists
- 4 InfiniPath Cluster Setup and Administration
- Introduction
- Installed Layout
- Memory Footprint
- BIOS Settings
- InfiniPath and OpenFabrics Driver Overview
- OpenFabrics Drivers and Services Configuration and Startup
- Other Configuration: Changing the MTU Size
- Managing the InfiniPath Driver
- More Information on Configuring and Loading Drivers
- Performance Settings and Management Tips
- Host Environment Setup for MPI
- Checking Cluster and Software Status
- 5 Using QLogic MPI
- Introduction
- Getting Started with MPI
- QLogic MPI Details
- Use Wrapper Scripts for Compiling and Linking
- Configuring MPI Programs for QLogic MPI
- To Use Another Compiler
- Process Allocation
- mpihosts File Details
- Using mpirun
- Console I/O in MPI Programs
- Environment for Node Programs
- Environment Variables
- Running Multiple Versions of InfiniPath or MPI
- Job Blocking in Case of Temporary InfiniBand Link Failures
- Performance Tuning
- MPD
- QLogic MPI and Hybrid MPI/OpenMP Applications
- Debugging MPI Programs
- QLogic MPI Limitations
- 6 Using Other MPIs
- A mpirun Options Summary
- B Benchmark Programs
- C Integration with a Batch Queuing System
- D Troubleshooting
- Using LEDs to Check the State of the Adapter
- BIOS Settings
- Kernel and Initialization Issues
- OpenFabrics and InfiniPath Issues
- Stop OpenSM Before Stopping/Restarting InfiniPath
- Manual Shutdown or Restart May Hang if NFS in Use
- Load and Configure IPoIB Before Loading SDP
- Set $IBPATH for OpenFabrics Scripts
- ifconfig Does Not Display Hardware Address Properly on RHEL4
- SDP Module Not Loading
- ibsrpdm Command Hangs when Two Host Channel Adapters are Installed but Only Unit 1 is Connected to the Switch
- Outdated ipath_ether Configuration Setup Generates Error
- System Administration Troubleshooting
- Performance Issues
- QLogic MPI Troubleshooting
- Mixed Releases of MPI RPMs
- Missing mpirun Executable
- Resolving Hostname with Multi-Homed Head Node
- Cross-Compilation Issues
- Compiler/Linker Mismatch
- Compiler Cannot Find Include, Module, or Library Files
- Problem with Shell Special Characters and Wrapper Scripts
- Run Time Errors with Different MPI Implementations
- Process Limitation with ssh
- Number of Processes Exceeds ulimit for Number of Open Files
- Using MPI.mod Files
- Extending MPI Modules
- Lock Enough Memory on Nodes When Using a Batch Queuing System
- Error Creating Shared Memory Object
- gdb Gets SIG32 Signal Under mpirun -debug with the PSM Receive Progress Thread Enabled
- General Error Messages
- Error Messages Generated by mpirun
- MPI Stats
- E Write Combining
- F Useful Programs and Files
- G Recommended Reading
- Glossary
- Index
5–Using QLogic MPI
Debugging MPI Programs
IB6054601-00 H 5-25
A
Debugging MPI Programs
Debugging parallel programs is substantially more difficult than debugging serial
programs. Thoroughly debugging the serial parts of your code before parallelizing
is good programming practice.
MPI Errors
Almost all MPI routines (except MPI_Wtime and MPI_Wtick) return an error
code; either as the function return value in C functions or as the last argument in a
Fortran subroutine call. Before the value is returned, the current MPI error handler
is called. By default, this error handler aborts the MPI job. Therefore, you can get
information about MPI exceptions in your code by providing your own handler for
MPI_ERRORS_RETURN. See the man page for the MPI_Errhandler_set for
details.
See the standard MPI documentation referenced in Appendix G for details on the
MPI error codes.
Using Debuggers
The InfiniPath software supports the use of multiple debuggers, including
pathdb, gdb, and the system call tracing utility strace. These debuggers let you
set breakpoints in a running program, and examine and set its variables.
Symbolic debugging is easier than machine language debugging. To enable
symbolic debugging, you must have compiled with the -g option to mpicc
so that
the compiler will have included symbol tables in the compiled object code.
To run your MPI program with a debugger, use the -debug
or
-debug-no-pause and -debugger options for mpirun. See the man pages to
pathdb, gdb, and strace for details. When running under a debugger, you get
an xterm window on the front end machine for each node process. Therefore, you
can control the different node processes as desired.
To use strace with your MPI program, the syntax is:
$ mpirun -np n -m mpihosts strace program-name
NOTE:
When there are more threads than CPUs, both MPI and OpenMP
performance can be significantly degraded due to over-subscription of the
CPUs.
NOTE:
MPI does not guarantee that an MPI program can continue past an error.