Overview of CrayPat and Apprentice 2 Adam Leko UPC Group HCS Research Laboratory University of Florida Color encoding key: Blue: Information Red: Negative note Green: Positive note

2 Basic Information Name: CrayPat, Apprentice 2 Developer: Cray Current Version:  CrayPat v  Apprentice 2 v2.0  (not available separately) Languages: Fortran, C, C++ Website: Documentation available at  Contact:  Luiz DeRose

3 CrayPat and Apprentice 2 Overview CrayPat  Cray’s toolkit for instrumenting executables and producing data from runs  Uses static binary instrumentation  Supports tracing, profiling, and sampling  Outputs data in binary format which can be converted to XML format (for Apprentice 2) Text format (report that contains statistical information) Apprentice 2  Visualization tool for CrayPat data files  Can read in.xml or.xml.gz files (gzipped XML reports converted from binary output of CrayPat)  Several visualizations available

4 CrayPat Overview Command-line based performance optimization tools In CrayPat, you perform experiments on instrumented executables  Several types of experiments available Tracing: Record timestamps and arguments for all instrumented functions Sampling: Samples hardware counters or callstack at fixed intervals Profiling: Performs a specific sampling experiment where user + system time are sampled for all functions in a program  Type of experiment guided by setting environment variables However, can only perform tracing experiments on executables instrumented for tracing But, can perform sample-type experiments on executables instrumented for tracing General workflow  1. Compile application and run as normal  2. Instrument using pat_build  3. Run instrumented executable as normal; binary.xf log file will be produced  4. View report using pat_report  Can also use pat_run to combine steps 3 & 4, or pat_hwpc on uninstrumented exectuables to get hardware counter reports CrayPat supports many languages + extensions  C, C++, Fortran, UPC, MPI, CoArray Fortran, OpenMP, SHMEM

5 CrayPat Instrumentation Instrumentation is very simple! Build application as normal (not even debugging symbols needed), keeping the.o files  Eg: UPC: cc -hupc -hkeepfiles *.upc -o exe C/C++/MPI C: cc -hkeepfiles *.c -o exe Fortran: ftn -hkeepfiles *.f77 -o exe Can also use -c flag with compilers and link in separate stage as normal Use pat_build to build instrumented executable  For profiling or sampling: pat_build exe inst.exe  For tracing: UPC: pat_build -g upc exe inst.exe MPI: pat_build -g mpi exe inst.exe Several other things can be traced with -g flag (CoArray Fortran, heap calls, I/O system calls Passing the -u flag also traces all (non-inlined) user function calls Then run program as normal as shown earlier Use of binary instrumentation means low overhead and no interference with compiler optimizations  X1 and X1E are extremely dependent on compiler optimizations (loop vectorization especially), so this is an absolute necessity for CrayPat  In our informal tests, sampling instrumentation resulted in negligible overhead (< 2-3 %)  Also,.xf logfiles from runs seem very compact

6 Sample pat_report Output By default, pat_report lists profile-type information Can also produce a listing of events with -c records option, but not very useful  Although necessary for exporting traces to Apprentice 2 Lots of different summary information can be displayed using pat_report  Output very customizable  Can change text format, how stats are computed, which data is displayed, …  Like prof on steroids Table 1: -d time%,cum_time%,time,traces,P,E,M -b exp,pe,thread,ssp,function,ca Time% | Cum.Time% | Time | Traces |Experiment=1 |PE=0 |Thread=0 |SSP=0 |Function |Caller 100.0% | 100.0% | | 72 |Total | | 100.0% | 100.0% | | 1 |main | | | | | (N/A) | 0.0% | 100.0% | | 45 |timer_now$$CFE_id_hex2UINT || || 0.0% | 100.0% | | 21 | timer_elapsed$$CFE_id_hex2UINT || | | | | main || 0.0% | 100.0% | | 24 |main ||====================================================== | 0.0% | 100.0% | | 2 |ioctl | | | | | printf | | | | | main | 0.0% | 100.0% | | 21 |timer_elapsed$$CFE_id_hex2UINT | | | | | main | 0.0% | 100.0% | | 1 |extendDC | | | | | main | 0.0% | 100.0% | | 1 |_exit | | | | | sigtramp | | | | | main | 0.0% | 100.0% | | 1 |hex2UINT | | | | | main |=======================================================

7 Apprentice 2 Overview Visualization tool for XML files produced by CrayPat Supports visualization of  Callstack sampling experiments  MPI trace experiments Available visualizations  Overview piecharts that contain a breakdown of data by time and calls  Traffic (timeline/Gantt chart)  Text report (similar to what is available from CrayPat)  Mosaic (shows communication volume between processing elements)  Activity (shows % time spent in different MPI functions as a function of time)  Profile (show call tree with observed times) Several visualizations also have “calipers” at bottom of screen to restrict view to certain time periods

8 Apprentice 2 Problems Was never able to get Apprentice 2 to run properly Followed instructions provided by Cray [1], but was never able to get Apprentice to show a callstack profile or an MPI trace  All visualizations looked empty!  See right for examples Probably due to using a (beta) public-access Cray machine Rest of information garnered from [2]

9 Apprentice 2 Visualizations Call graph view  Shows summary of sampled call stacks  Similar to display of KCacheGrind  Inclusive/exclusive time annotated by height and width of functions

10 Apprentice 2 Visualizations (2) Overview display  Overview shows breakdown of execution time by each function in a pie chart  Clicking on each function brings up a tab showing breakdown per node  Clicking on “other” brings up text list of other functions Can also display pie chart of function times by node

11 Apprentice 2 Visualizations (3) Timeline view  Shows communication in Gantt chart view  Similar to other trace-based MPI visualization tools

12 Apprentice 2 Visualizations (4) Mosaic view  Shows pair-wise communication statistics  Can show different stats Max time Average time Min time

13 Apprentice 2 Visualizations (5) Activity view  Shows percentage of time spent in MPI calls as a function of time  Ex: Red = barrier Light green = broadcast Dark green = send

14 References [1]“Optimizing Applications on Cray X1 Series Systems,” #S , (available from docs.cray.com) [2]L. DeRose, “Performance Analysis and Visualization with Cray Apprentice 2,” SC 2004, Pittsburgh, PA, November 2004.