98 lines
3.0 KiB
Markdown
98 lines
3.0 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/.
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It contains the following streaming kernels with corresponding data access pattern (Notation: S - store, L - load, WA - write allocate):
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* init (S1, WA): Initilize an array. Store only.
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* sum (L1): Vector reduction. Load only.
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* copy (L1, S1, WA): Classic memcopy.
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* update (L1, S1): Update a vector. Also load + store but without write allocate.
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* triad (L2, S1, WA): Stream triad - `a = b + b * 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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## Build
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1. Configure the toolchain to use in the `Makefile`:
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```
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TAG = GCC # Supported GCC, CLANG, ICC
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```
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2. Review the flags for toolchain in the corresponding included file, e.g. `include_GCC.mk`. OpenMP is disabled per default, you can enable it by uncommenting the OpenMP flag:
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```
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OPENMP = -fopenmp
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```
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3. 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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4. 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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5. (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) Avg time Min time Max time
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Init: 14681.5000 0.0110 0.0109 0.0111
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Sum: 20634.9290 0.0079 0.0078 0.0082
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Copy: 18822.2827 0.0172 0.0170 0.0176
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Update: 28135.9717 0.0115 0.0114 0.0117
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Triad: 19263.0634 0.0253 0.0249 0.0268
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Daxpy: 26718.1377 0.0182 0.0180 0.0187
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STriad: 21229.4470 0.0305 0.0301 0.0313
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SDaxpy: 26714.3897 0.0243 0.0240 0.0253
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-------------------------------------------------------------
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Solution Validates
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```
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