105 lines
3.6 KiB
Markdown
105 lines
3.6 KiB
Markdown
# The Bandwidth Benchmark
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This is a collection of simple streaming kernels for teaching purposes.
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It is heavily inspired by John McCalpin's https://www.cs.virginia.edu/stream/ benchmark.
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It contains the following streaming kernels with corresponding data access pattern (Notation: S - store, L - load, WA - write allocate). All variables are vectors, s is a scalar:
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* init (S1, WA): Initilize an array: `a = s`. Store only.
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* sum (L1): Vector reduction: `s += a`. Load only.
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* copy (L1, S1, WA): Classic memcopy: `a = b`.
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* update (L1, S1): Update vector: `a = a * scalar`. Also load + store but without write allocate.
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* triad (L2, S1, WA): Stream triad: `a = b + c * scalar`.
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* daxpy (L2, S1): Daxpy: `a = a + b * scalar`.
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* striad (L3, S1, WA): Schoenauer triad: `a = b + c * d`.
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* sdaxpy (L3, S1): Schoenauer triad without write allocate: `a = a + b * c`.
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As added benefit the code is a blueprint for a minimal benchmarking application with a generic makefile and modules for aligned array allocation, accurate timing and affinity settings. Those components can be used standalone in your own project.
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## Build
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1. Configure the toolchain and additional options in `config.mk`:
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```
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# Supported: GCC, CLANG, ICC
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TAG ?= GCC
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ENABLE_OPENMP ?= false
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OPTIONS = -DSIZE=40000000ull
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OPTIONS += -DNTIMES=10
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OPTIONS += -DARRAY_ALIGNMENT=64
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#OPTIONS += -DVERBOSE_AFFINITY
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#OPTIONS += -DVERBOSE_DATASIZE
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#OPTIONS += -DVERBOSE_TIMER
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```
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The verbosity options enable detailed output about affinity settings, allocation sizes and timer resolution.
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2. Build with:
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```
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make
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```
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You can build multiple toolchains in the same directory, but notice that the Makefile is only acting on the one currently set. Intermediate build results are located in the `<TOOLCHAIN>` directory.
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To output the executed commands use:
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```
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make Q=
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```
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3. Clean up with:
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```
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make clean
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```
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to clean intermediate build results.
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```
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make distclean
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```
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to clean intermediate build results and binary.
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4. (Optional) Generate assembler:
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```
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make asm
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```
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The assembler files will also be located in the `<TOOLCHAIN>` directory.
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## Usage
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To run the benchmark call:
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```
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./bwBench-<TOOLCHAIN>
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```
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The benchmark will output the results similar to the stream benchmark. Results are validated.
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For threaded execution it is recommended to control thread affinity.
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We recommend to use likwid-pin for benchmarking:
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```
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likwid-pin -c 0-3 ./bwbench-GCC
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```
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Example output for threaded execution:
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```
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-------------------------------------------------------------
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[pthread wrapper]
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[pthread wrapper] MAIN -> 0
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[pthread wrapper] PIN_MASK: 0->1 1->2 2->3
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[pthread wrapper] SKIP MASK: 0x0
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threadid 140271463495424 -> core 1 - OK
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threadid 140271455102720 -> core 2 - OK
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threadid 140271446710016 -> core 3 - OK
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OpenMP enabled, running with 4 threads
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----------------------------------------------------------------------------
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Function Rate(MB/s) Rate(MFlop/s) Avg time Min time Max time
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Init: 22111.53 - 0.0148 0.0145 0.0165
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Sum: 46808.59 46808.59 0.0077 0.0068 0.0140
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Copy: 30983.06 - 0.0207 0.0207 0.0208
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Update: 43778.69 21889.34 0.0147 0.0146 0.0148
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Triad: 34476.64 22984.43 0.0282 0.0278 0.0305
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Daxpy: 45908.82 30605.88 0.0214 0.0209 0.0242
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STriad: 37502.37 18751.18 0.0349 0.0341 0.0388
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SDaxpy: 46822.63 23411.32 0.0281 0.0273 0.0325
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----------------------------------------------------------------------------
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Solution Validates
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```
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