The Jacquard Programming Environment Mike Stewart NUG User Training, 10/3/05

2 Outline Compiling and Linking. Optimization. Libraries. Debugging. Porting from Seaborg and other systems.

3 Pathscale Compilers Default compilers: Pathscale Fortran 90, C, and C++. Module “path” is loaded by default and points to the current default version of the Pathscale compilers (currently 2.2.1). Other versions available: module avail path. Extensive vendor documentation available on-line at Commercial product: well supported and optimized.

4 Compiling Code Compiler invocation: –No MPI: pathf90, pathcc, pathCC. –MPI: mpif90, mpicc, mpicxx The mpi compiler invocation will use the currently loaded compiler version. The mpi and non-mpi compiler invocations have the same options and arguments.

5 Compiler Optimization Options 4 numeric levels –On where n ranges from 0 (no optimization) to 3. Default level: -O2 (unlike IBM) –g without a –O option changes the default to –O0.

6 -O1 Optimization Minimal impact on compilation time compared to –O0 compile. Only optimizations applied to straight line code (basic blocks) like instruction scheduling.

7 -O2 Optimization Default when no optimization arguments given. Optimizations that always increase performance. Can significantly increase compilation time. -O2 optimization examples: –Loop nest optimization. –Global optimization within a function scope. –2 passes of instruction scheduling. –Dead code elimination. –Global register allocation.

8 -O3 Optimization More extensive optimizations that may in some cases slow down performance. Optimizes loop nests rather than just inner loops, i.e. inverts indices, etc. “Safe” optimizations – produces answers identical with those produced by –O0. NERSC recommendation based on experiences with benchmarks.

9 -Ofast Optimization Equivalent to -O3 -ipa -fno-math-errno -OPT:roundoff=2:Olimit=0:div_split=ON:alias=typed. ipa – interprocedural analysis. –Optimizes across functional boundaries. –Must be specified both at compile and link time. Aggressive “unsafe” optimizations: –Changes order of evaluation. –Deviates from IEEE 754 standard to obtain better performance. There are some known problems with this level of optimization in the current release,

10 NAS B Serial Benchmarks Performance (MOP/S) Seaborg Best -O0-O1-O2-O3-Ofast BT CG EP FT did not compile IS LU MG SP

11 NAS B Serial Benchmarks Compile Times (seconds) -O0-O1-O2-O3-Ofast BT CG EP FT did not compile IS LU MG SP

12 NAS B Optimization Arguments Used by LNXI Benchmarkers BenchmarkArguments BT-O3 -ipa -WOPT:aggstr=off CG-O3 -ipa -CG:use_movlpd=on -CG:movnti=1 EP-LNO:fission=2 -O3 -LNO:vintr=2 FT-O3 -LNO:opt=0 IS-Ofast -DUSE_BUCKETS LU-Ofast -LNO:fusion=2:prefetch=0:full_unroll=10:ou_max=5 -OPT:ro=3:fold_unsafe_relops=on:fold_unsigned_relops=on: unroll_size=256:unroll_times_max=16:fast_complex -CG:cflow=off:p2align_freq=1 -fno-exceptions MG-O3 -ipa -WOPT:aggstr=off -CG:movnti=0 SP-Ofast

13 NAS C FT (32 Proc) OptimizationMops/ProcCompile Time (seconds) Seaborg Best 86.5N/A -O O O O Ofast

14 SuperLU MPI Benchmark Based on the SuperLU general purpose library for the direct solution of large, sparse, nonsymmetric systems of linear equations. Mostly C with some Fortran 90 routines. Run on 64 processors/32 nodes. Uses BLAS routines from ACML.

15 SLU (64 procs) OptimizationElapsed run time (seconds) Compile Time (seconds) Seaborg Best 742.5N/A -O O O O OfastN/ADid not compile

16 Jacquard Applications Acceptance Benchmarks BenchmarkSeaborgJacquardJacquard Optimizations NAMD (32 proc)2384 sec554-O3 -ipa -fno-exceptions Chombo Serial1036 sec138-O3 -OPT:Ofast -OPT:Olimit= fno-math-errno -finline Chombo Parallel (32 proc) 773 sec161-O3 -OPT:Ofast -OPT:Olimit= fno-math-errno -finline CAM Serial sec264-O2 CAM Parallel (32 proc) 75 sec13.2-O2 SuperLU (64 proc) sec212-O3 -OPT:Ofast -fno-math-errno

17 ACML Library AMD Core Math Library - set of numerical routines tuned specifically for AMD64 platform processors. –BLAS –LAPACK –FFT To use with pathscale: –module load acml (built with pathscale compilers) –Compile and link with $ACML To use with gcc: –module load acml_gcc (build with pathscale compilers) –Compile and link with $ACML

18 Matrix Multiply Optimization Example 3 ways to multiply 2 dense matrices –Directly in Fortran with nested loops –Matmul F90 intrinsic –dgemm from ACML Example by 1000 double precision matrices. Order of indices: ijk means – do i=1,n – do j=1,n – do k=1,n

19 Fortran Matrix Multiply MFLOPs Seaborg Best -O0 -O1 -O2 -O3-Ofast ijk jik ikj kij jki kji matmul dgemm

20 Debugging Etnus Totalview debugger has been installed on the system. Still in testing mode, but it should be available to users soon.

21 Porting codes Jacquard is a linux system so gnu tools like gmake are the defaults. Pathscale compilers are good, but new, so please report any evident compiler bugs to consult.