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Update README for new results
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‎README.org‎

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This repository contains John D. McCalpin's [[https://www.cs.virginia.edu/stream/][STREAM benchmark]] and a
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port of that benchmark to ISPC. The port to ISPC also uses dynamic
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memory allocation.
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memory allocation, and it provides a straightforward way to
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ensure that streaming/"non-temporal" stores are used.
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** Building
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There is a =Makefile= provided to build the two benchmark codes.
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You may need to edit the =Makefile= to adjust compilers and
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compiler flags for your system. To build just run =make= and the
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executable files =build/stream= and =build/stream_ispc= should be
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built.
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There is a =Makefile= provided to build the two benchmark codes.
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You may need to edit the =Makefile= to adjust compilers and
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compiler flags for your system. To build just run =make= and the
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executable files =build/stream=, =build/stream_ispc=
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=build/stream_ispc_loopy= should be built. Only the latter version
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uses streaming stores.
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** Performance Results (aka =icc= vs =ispc=)
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** Performance Results
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I compared =build/stream= and =build/stream_ispc= on a dual socket
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Xeon CPU E5-2698 v3 system. I used the following build flags
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These results were obtained on a Raptor Lake (i7-1365U) laptop.
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#+BEGIN_SRC
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CC=icc
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CFLAGS=-std=gnu99 -g -xHOST -O3 -ffreestanding -openmp
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Here is the version information for the compilers we are using:
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CXX=icpc
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CXXFLAGS=-g -xHOST -O3 -ffreestanding -openmp -DISPC_USE_OMP
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ISPC = ispc
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ISPCFLAGS = --target=avx2-i32x8 --pic --opt=force-aligned-memory --werror
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#+END_SRC
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Here is the version information for the compilers we are using:
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#+BEGIN_SRC sh :exports both
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icc --version
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#+BEGIN_SRC sh :exports both
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gcc --version
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#+END_SRC
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#+results:
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: icc (ICC) 16.0.1 20151021
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: Copyright (C) 1985-2015 Intel Corporation. All rights reserved.
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#+results:
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: gcc (Debian 14.2.0-16) 14.2.0
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: Copyright (C) 2024 Free Software Foundation, Inc.
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: This is free software; see the source for copying conditions. There is NO
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: warranty; not even for MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.
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#+BEGIN_SRC sh :exports both
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ispc --version
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#+END_SRC
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#+results:
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: Intel(r) SPMD Program Compiler (ispc), 1.9.0 (build commit 89dfbf2125fc2cba @ 20160212, LLVM 3.8)
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Here is the output from the STREAM benchmark compiled with =icc=:
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#+BEGIN_SRC sh :exports both
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OMP_PLACES=cores OMP_DISPLAY_ENV=true ./build/stream
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#+END_SRC
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#+results:
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: -------------------------------------------------------------
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: STREAM version $Revision: 5.10 $
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: -------------------------------------------------------------
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: This system uses 4 bytes per array element.
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: -------------------------------------------------------------
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: Array size = 80000000 (elements), Offset = 0 (elements)
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: Memory per array = 305.2 MiB (= 0.3 GiB).
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: Total memory required = 915.5 MiB (= 0.9 GiB).
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: Each kernel will be executed 10 times.
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: The *best* time for each kernel (excluding the first iteration)
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: will be used to compute the reported bandwidth.
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: -------------------------------------------------------------
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:
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: OPENMP DISPLAY ENVIRONMENT BEGIN
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: _OPENMP='201307'
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: [host] OMP_CANCELLATION='FALSE'
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: [host] OMP_DISPLAY_ENV='TRUE'
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: [host] OMP_DYNAMIC='FALSE'
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: [host] OMP_MAX_ACTIVE_LEVELS='2147483647'
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: [host] OMP_NESTED='FALSE'
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: [host] OMP_NUM_THREADS: value is not defined
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: [host] OMP_PLACES='cores'
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: [host] OMP_PROC_BIND='spread'
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: [host] OMP_SCHEDULE='static'
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: [host] OMP_STACKSIZE='4M'
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: [host] OMP_THREAD_LIMIT='2147483647'
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: [host] OMP_WAIT_POLICY='PASSIVE'
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: OPENMP DISPLAY ENVIRONMENT END
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:
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:
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: Number of Threads requested = 32
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: Number of Threads counted = 32
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: -------------------------------------------------------------
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: Your clock granularity/precision appears to be 1 microseconds.
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: Each test below will take on the order of 5419 microseconds.
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: (= 5419 clock ticks)
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: Increase the size of the arrays if this shows that
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: you are not getting at least 20 clock ticks per test.
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: -------------------------------------------------------------
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: WARNING -- The above is only a rough guideline.
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: For best results, please be sure you know the
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: precision of your system timer.
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: -------------------------------------------------------------
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: Function Best Rate MB/s Avg time Min time Max time
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: Copy: 104902.7 0.006141 0.006101 0.006308
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: Scale: 106522.0 0.006039 0.006008 0.006146
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: Add: 112215.9 0.008605 0.008555 0.008762
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: Triad: 112097.2 0.008595 0.008564 0.008710
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: -------------------------------------------------------------
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: Solution Validates: avg error less than 1.000000e-06 on all three arrays
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: Results Validation Verbose Results:
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: Expected a(1), b(1), c(1): 1153300692992.000000 230660145152.000000 307546849280.000000
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: Observed a(1), b(1), c(1): 1153300824064.000000 230660161536.000000 307546882048.000000
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: Rel Errors on a, b, c: 1.136495e-07 7.103091e-08 1.065464e-07
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: -------------------------------------------------------------
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#+BEGIN_SRC sh :exports both
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ispc --version
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#+END_SRC
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#+results:
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: Intel(r) Implicit SPMD Program Compiler (Intel(r) ISPC), 1.25.3 (build @ 20241223, LLVM 19.1.6)
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Here is the output from the STREAM benchmark compiled with =gcc=:
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#+BEGIN_SRC sh :exports both
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OMP_PLACES=cores OMP_DISPLAY_ENV=true ./build/stream
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#+END_SRC
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#+results:
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: OPENMP DISPLAY ENVIRONMENT BEGIN
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: _OPENMP = '201511'
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: [host] OMP_DYNAMIC = 'FALSE'
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: [host] OMP_NESTED = 'FALSE'
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: [host] OMP_NUM_THREADS = '1'
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: [host] OMP_SCHEDULE = 'DYNAMIC'
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: [host] OMP_PROC_BIND = 'FALSE'
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: [host] OMP_PLACES = '{0:2},{2:2},{4},{5},{6},{7},{8},{9},{10},{11}'
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: [host] OMP_STACKSIZE = '0'
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: [host] OMP_WAIT_POLICY = 'PASSIVE'
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: [host] OMP_THREAD_LIMIT = '4294967295'
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: [host] OMP_MAX_ACTIVE_LEVELS = '1'
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: [host] OMP_NUM_TEAMS = '0'
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: [host] OMP_TEAMS_THREAD_LIMIT = '0'
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: [all] OMP_CANCELLATION = 'FALSE'
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: [all] OMP_DEFAULT_DEVICE = '0'
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: [all] OMP_MAX_TASK_PRIORITY = '0'
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: [all] OMP_DISPLAY_AFFINITY = 'FALSE'
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: [host] OMP_AFFINITY_FORMAT = 'level %L thread %i affinity %A'
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: [host] OMP_ALLOCATOR = 'omp_default_mem_alloc'
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: [all] OMP_TARGET_OFFLOAD = 'DEFAULT'
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: OPENMP DISPLAY ENVIRONMENT END
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: -------------------------------------------------------------
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: STREAM version $Revision: 5.10 $
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: -------------------------------------------------------------
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: This system uses 4 bytes per array element.
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: -------------------------------------------------------------
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: Array size = 80000000 (elements), Offset = 0 (elements)
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: Memory per array = 305.2 MiB (= 0.3 GiB).
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: Total memory required = 915.5 MiB (= 0.9 GiB).
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: Each kernel will be executed 10 times.
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: The *best* time for each kernel (excluding the first iteration)
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: will be used to compute the reported bandwidth.
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: -------------------------------------------------------------
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: Number of Threads requested = 12
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: Number of Threads counted = 12
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: -------------------------------------------------------------
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: Your clock granularity/precision appears to be 1 microseconds.
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: Each test below will take on the order of 11368 microseconds.
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: (= 11368 clock ticks)
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: Increase the size of the arrays if this shows that
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: you are not getting at least 20 clock ticks per test.
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: -------------------------------------------------------------
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: WARNING -- The above is only a rough guideline.
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: For best results, please be sure you know the
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: precision of your system timer.
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: -------------------------------------------------------------
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: Function Best Rate MB/s Avg time Min time Max time
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: Copy: 45432.1 0.029872 0.014087 0.049874
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: Scale: 44736.3 0.035883 0.014306 0.051508
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: Add: 48758.6 0.035604 0.019689 0.070311
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: Triad: 49037.1 0.032059 0.019577 0.060323
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: -------------------------------------------------------------
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: Solution Validates: avg error less than 1.000000e-06 on all three arrays
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: Results Validation Verbose Results:
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: Expected a(1), b(1), c(1): 1153300692992.000000 230660145152.000000 307546849280.000000
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: Observed a(1), b(1), c(1): 1153300824064.000000 230660161536.000000 307546882048.000000
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: Rel Errors on a, b, c: 2.383402e-08 1.489626e-08 2.234439e-08
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: -------------------------------------------------------------
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Here is the output from the modified STREAM benchmark with kernels
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compiled with =ispc=:
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#+BEGIN_SRC sh :exports both
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OMP_PLACES=cores OMP_DISPLAY_ENV=true ./build/stream_ispc
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#+END_SRC
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#+results:
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: Array size = 80000000 (elements)
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: Memory per array = 305.2 MiB (= 0.3 GiB).
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: Total memory required = 915.5 MiB (= 0.9 GiB).
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: Chunk size: 16384
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: Page size: 4096
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: Cache line size: 64
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: sizeof(STREAM_TYPE): 4
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: Each kernel will be executed 10 times.
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: The *best* time for each kernel (excluding the first iteration)
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: will be used to compute the reported bandwidth.
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: -------------------------------------------------------------
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:
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: OPENMP DISPLAY ENVIRONMENT BEGIN
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: _OPENMP='201307'
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: [host] OMP_CANCELLATION='FALSE'
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: [host] OMP_DISPLAY_ENV='TRUE'
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: [host] OMP_DYNAMIC='FALSE'
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: [host] OMP_MAX_ACTIVE_LEVELS='2147483647'
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: [host] OMP_NESTED='FALSE'
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: [host] OMP_NUM_THREADS: value is not defined
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: [host] OMP_PLACES='cores'
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: [host] OMP_PROC_BIND='spread'
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: [host] OMP_SCHEDULE='static'
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: [host] OMP_STACKSIZE='4M'
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: [host] OMP_THREAD_LIMIT='2147483647'
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: [host] OMP_WAIT_POLICY='PASSIVE'
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: OPENMP DISPLAY ENVIRONMENT END
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:
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:
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: -------------------------------------------------------------
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: Each test below will take on the order of 6482 microseconds.
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: -------------------------------------------------------------
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: -------------------------------------------------------------
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: Function Best Rate MB/s Avg time Min time Max time
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: Copy: 75179.7 0.008546 0.008513 0.008603
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: Scale: 73558.4 0.008729 0.008701 0.008792
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: Add: 83152.5 0.011573 0.011545 0.011613
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: Triad: 83805.1 0.011485 0.011455 0.011520
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: -------------------------------------------------------------
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: Solution Validates: avg error less than 1.000000e-06 on all three arrays
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: Results Validation Verbose Results:
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: Expected a(1), b(1), c(1): 1153300692992.000000 230660145152.000000 307546849280.000000
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: Observed a(1), b(1), c(1): 1153300824064.000000 230660161536.000000 307546882048.000000
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: Rel Errors on a, b, c: 1.136495e-07 7.103091e-08 1.065464e-07
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: -------------------------------------------------------------
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Here is the output from the modified STREAM benchmark with kernels
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compiled with =ispc= using =ispc='s high-level loop constructs and
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without streaming stores:
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#+BEGIN_SRC sh :exports both
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OMP_PLACES=cores OMP_DISPLAY_ENV=true ./build/stream_ispc
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#+END_SRC
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#+results:
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: -------------------------------------------------------------
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: Function Best Rate MB/s Avg time Min time Max time
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: Copy: 49986.2 0.013017 0.012804 0.013866
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: Scale: 49472.4 0.013018 0.012937 0.013115
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: Add: 52357.1 0.018545 0.018336 0.019054
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: Triad: 52421.3 0.019951 0.018313 0.030611
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: -------------------------------------------------------------
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As we can see the =icc= version is about 1.3x faster than the
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=ispc= version. I tried various memory alignment procedures but
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could not improve the performance of the =ispc= version of the
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benchmark.
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And here is the output from the modified STREAM benchmark with kernels
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compiled with =ispc= using kernels generated by [[https://github.com/inducer/loopy][loopy]], including the
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use of streaming stores:
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#+BEGIN_SRC sh :exports both
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OMP_PLACES=cores OMP_DISPLAY_ENV=true ./build/stream_ispc_loopy
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#+END_SRC
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#+results:
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: -------------------------------------------------------------
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: Function Best Rate MB/s Avg time Min time Max time
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: Copy: 65615.9 0.015429 0.009754 0.030991
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: Scale: 66276.3 0.015031 0.009657 0.031078
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: Add: 63480.7 0.017027 0.015123 0.029783
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: Triad: 63078.4 0.019036 0.015219 0.028874
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: -------------------------------------------------------------

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