# Presentation: 359755

**User Tools for BlueGene/L and Purple**

**Scott Futral**
**Development Environment Group**
**Advanced Simulation and Computing****Lawrence Livermore National Laboratory**
**February 24, 2005**

*This work was performed under the auspices of the U.S. Department of Energy by the University of California Lawrence Livermore National Laboratory under Contract No. W-7405-Eng-48.*
*UCRL-PRES-2099373*

- UNCLASSIFIED

- UNCLASSIFIED

## Overview

**Status of Purple code development tools**
**Compilers**
**Debuggers**
**Profiling and performance tools**
**Status of BlueGene/L tools**
**Some unique aspects of BG/L**
**Tools available and possible**
**Getting info from LC Web pages**

## Purple Development Environment: “A lot like White!”

**The standard AIX environment available (AIX 5.3)**
**IBM XL & GNU compilers**
**IBM Math libraries (PESSL)**
**Standard Unix tools**
**Open source and third-party tools and libraries (Python, Perl, math libs, graphics packages...)**
**TotalView Debugger**
**Forward compatibility for applications built on White**
**LCRM batch system**

## Some differences for Purple that could matter

**Federation Switch and IBM MPI**
**SLURM resource management- is it transparent?**
**Large Memory pages may have performance impact on some apps**
**64-bit kernel and default 64-bit apps will cause some changes**
**Zerofault memory debugger NOT available for 64-bit apps**
**IBM Purify beta was D.O.A.**
**Will other commercial tools be affected?**

## Example of Zerofault GUI

## Purple Statement of Work (SOW) Performance Tool Requirements

**Profiling**
**Event Tracing**
**Cluster Wide Development Tool API**
**Cluster Wide Development Tool GUI**
**Lightweight corefiles**
**Timer API**

## Performance Tools for Purple SOW

**PE Benchmarker (PEB)**
**Dynamic Probe Class Library (DPCL)**
**Intel Trace Collector (ITC)**
**Intel Trace Analyzer (ITA)**

## Purple SOW Profiling Requirements

**Profile at source block level (PEB)**
**Profiling tool scales to entire system (PEB)**
**Profile types**
**CPU time (PEB)**
**HPM (PEB)**
**Page Faults (PEB)**
**(MPI?) I/O (ITC)**
**MPI send/recv bytes (ITC/PEB)**
**Memory usage with source reference (Purify?)**
**OpenMP (PEB)**

## PE Benchmarker Status

**IBM has provided 4.2 alpha release**
**Substantial improvement**
**Fixes for large applications**
**Improvements to clients**
**Some problems identified that will be reported**
**Release includes new SOW features**
**DPCL/PEB block-level instrumentation**
**OpenMP tool **
**MPI/LAPI communication volume profiling **
**Visualizer GUI features**
**Additional Features**

## PE Benchmarker Issues

**Java GUI performance problems**
**Slow performance with Java**
**Potential LLNL network issue**
**DPCL is unreliable**
**Often requires manual cleanup**
**system processes**
**user processes**
**shared memory segments**
**IBM has identified problem scenarios**
**LLNL can provide system resources to developers**
**Client interface issues**

## Purple SOW Tracing Requirements

**Time-stamped event records for all processes/threads (ITC)**
**MPI tracing (ITC)**
**Lightweight MPI callsite time and count statistics (?)**
**Scale to cluster-wide applications (ITC)**
**Support all baseline languages (ITC)**
**Translate traces to ASCII (ITC)**
**Self-defining format (not done by ITC)**
**Dynamic activation**
**From within a process (ITC)**
**From outside a process (ITC?)**
**Should not be a default requirement (ITC)**

## Brief Tracing Tool History

**Inception**
**Vampir : Forschungszentrum Juelich**
**Pallas Product**
**Vampir : Wolfgang Nagel, TU-Dresden**
**Vampirtrace : Pallas HPC Group**
**ASCI VampirGuideView Pathforward**
**Vampir, VampirNextGeneration : TU-Dresden**
**Vampirtrace : Pallas HPC Group ****→ Intel**
**Post Pathforward**
**Vampir, VampirNextGeneration : TU-Dresden**
**Intel Trace Collector/Analyzer : Intel**

## Intel Trace Collector/Analyzer Status

**LLNL has not received Purple version of ITC/ITA from Intel or IBM**
**Remarks from Intel**
**Purple will use a new IBM port of ITC**
**ITA trace visualization from an Intel system**
**Vampir or VampirNextGeneration on AIX**
**If STF tracefile format remains consistent**

## Cluster Wide Tool API 

**A means for dynamically activating and deactivating, reading, and resetting data for profiling, trace, and performance statistic instrumentation.  (DPCL)**
**The API shall dynamically control, activate, and deactivate the instrumentation of portions of an application during execution.  (DPCL)**
**The University’s strong preference is for the Open Source DPCL library and run-time infrastructure **

## Cluster Wide Tool GUI 

**Vampir / Vampirtrace are specified**
**ITC / ITA will address these requirements**
**Trace analysis of an MPI/threaded application running over an entire EDTV and Purple system**

## BlueGene/L Development Environment-Some challenges

**Front End node (FEN) operating system is SuSE SLES 9 Linux/Power**
**Compute nodes (CN) have a microkernel operating system with function shipping to I/O service nodes**
**Shared objects are not supported on the CNs**
**Threads are not supported on the CNs**
**No virtual memory support on the CN**
**Double wide FPU (double hummer) on the PowerPC 440 cores**
**Kernel is still in rapid development, so driver levels are evolving**
**There is no way to connect to stdin/stdout in an interactive fashion**

## BlueGene/L Development Environment-Implications

**FENs will have a rich development environment, with a familiar Linux feel!**
**Some tools from Linux/Intel environments may not be available or as robust on Linux/Power. (Valgrind is one example.)**
**CNs have limited tools available.**
**Code steering via run/proxy is not available.**
**Python not available on CNs**
**Tools that instrument at compile/link time are feasible (TAU, mpiP, MPI_prof)**
**Post-processing analyzers are possible (Paraver, mpip_insert_src)**

## BlueGene/L Tools- What’s available?

**IBM XL compilers (9.1Fortran, 7.0C/C++) with extensions to support****the SIMD aspect of the ‘double hummer’.**
**Optimized common vector intrinsics being integrated into compiler**
**BLAS/LAPACK**
**PAPI access to hardware counters was working on a previous driver level. **
**mpiP and MPI_trace for MPI profiling**
**TAU profiling layer**
**To quote Bob Walkup, "The best performance tool for BGL is a Power 4 system with HPMcount!"**

**Notes:**
“Currently the counters do not sample the entire range of operations, and in most cases cannot break distinguish between adds and subtracts, or multiplies and divides ! Jim Sexton has written a tool that will provide approximate upper and lower bounds for peak performance based on heuristics.”

## BlueGene/L Tools- TotalView Debugger status

**TotalView debugger is ported through a contract with the vendor Etnus. The main component of the contract was the purchase of a license and 3 years of support for about $1M.**
**The initial tool has been delivered and works! **
**BGL TV will support most basic debugging functionality including watchpoints.**
**IBM and Etnus to provide bug fixes before making TV available to our users**
**The target driver for TV Limited Availiability is driver 040**
**Etnus is still working to deliver a milestone which targets performance and scalability tuning. Progress is gated by large system availability.**

## BlueGene/L Tools- What’s possible?

**David Skinner of LBL is working with us to port IPM ("IPM is a portable profiling infrastructure which provides users with a concise report on the execution of parallel jobs.“)**
**A scalable Opentrace format could be developed that would enable tracing through TAU to be analyzed by VNG tool.**
**With effort and $’s, more sophisticated tools can be architected to work on BGL (TotalView!)**
**Valgrind memory tool in the future through a TRI-LAB EFFORT if funding is available. This will have limitations due to memory requirements of the tool.**
**Totalview memory debugger capability could be provided for ~$250k**
**A ‘static’ Python version?**
**DPCL (dynamic probe class library)**
**PAPI3**
**Leverage BlueGene/L consortium effort**

## Web Information on Tools

**http://www.llnl.gov/computing/hpc/code/software_tools.html**