From c2aa23aee4f8439dc1a3d4e0f845d54c1577c9be Mon Sep 17 00:00:00 2001
From: Christoph Lehmann <christoph.lehmann@ufz.de>
Date: Mon, 31 Jul 2017 13:23:29 +0200
Subject: [PATCH] added compile time measurement page
---
dev/compile-time-measurement/README.md | 111 +++++++++++++++++++++++++
1 file changed, 111 insertions(+)
create mode 100644 dev/compile-time-measurement/README.md
diff --git a/dev/compile-time-measurement/README.md b/dev/compile-time-measurement/README.md
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+Measured compilation time after changing a single file of the OGS sources.
+This should resemble the usual process development work.
+
+# Summary
+
+Compiling with fixed-size Eigen matrices takes significantly longer than with
+dynamic-sized Eigen matrices.
+
+# Used script
+
+```{sh}
+#!/bin/sh
+
+set -e
+
+export MAKEFLAGS="-j3"
+
+(
+ cd ../src
+ if [ "`git status --porcelain | wc -l`" -ne 0 ]; then
+ echo "Source directory contains untracked/uncommitted changes. Aborting" >&2
+ exit 1
+ fi
+) || exit 1
+
+
+if ! mkdir "build" &>/dev/null; then
+ echo "WARNING: reusing existing build directory!" >&2
+ read -r -p "Hit enter to continue "
+fi
+
+cd build
+
+# set some cmake option I usually use
+if ! cmake ../../src \
+ -DCMAKE_BUILD_TYPE=Release \
+ -DOGS_EIGEN_DYNAMIC_SHAPE_MATRICES=ON \
+ -DOGS_USE_LIS=ON;
+then
+ # workaround for second git worktree
+ (
+ cd CMakeFiles/git-data
+ ln -s HEAD head-ref
+ )
+ cmake .
+fi
+
+# initial build in fresh build directory
+time make ogs
+
+# make a non-trivial change to the code
+echo "inline void unused_dummy_function() {}" >> ../../src/ProcessLib/TES/TESLocalAssemblerInner.h
+
+# supposedly faster second build
+time make ogs
+```
+
+# Some results
+
+Summary: Initial compile time: ~ 10 minutes, compilation of changes only: ~ 16 seconds.
+Changing only ProcessLib/SmallDeformation/SmallDeformationFEM.h took ~20 seconds in the second build.
+
+```
+[...]
+Scanning dependencies of target ogs
+[100%] Building CXX object Applications/CLI/CMakeFiles/ogs.dir/ogs.cpp.o
+[100%] Linking CXX executable ../../bin/ogs
+[100%] Built target ogs
+
+real 9m47,808s
+user 24m2,080s
+sys 1m25,050s
+[ 5%] Built target logog
+[ 10%] Built target BaseLib
+[ 19%] Built target MathLib
+[ 28%] Built target GeoLib
+[ 47%] Built target MeshLib
+[ 52%] Built target MeshGeoToolsLib
+[ 61%] Built target NumLib
+[ 75%] Built target MaterialLib
+Scanning dependencies of target ProcessLib
+[ 75%] Building CXX object ProcessLib/CMakeFiles/ProcessLib.dir/TES/CreateTESProcess.cpp.o
+[ 75%] Building CXX object ProcessLib/CMakeFiles/ProcessLib.dir/TES/TESLocalAssemblerInner.cpp.o
+[ 77%] Building CXX object ProcessLib/CMakeFiles/ProcessLib.dir/TES/TESProcess.cpp.o
+[ 77%] Building CXX object ProcessLib/CMakeFiles/ProcessLib.dir/TES/TESReactionAdaptor.cpp.o
+[ 78%] Linking CXX static library ../lib/libProcessLib.a
+[100%] Built target ProcessLib
+[100%] Built target ApplicationsLib
+[100%] Linking CXX executable ../../bin/ogs
+[100%] Built target ogs
+
+real 0m15,544s
+user 0m26,212s
+sys 0m1,759s
+```
+
+## For reference: fixed-size Eigen matrices, three threads, ccache not disabled (but maybe not effective)
+
+initial build:
+```
+real 55m52,166s
+user 63m0,470s
+sys 7m32,749s
+```
+
+build after change:
+```
+real 2m6,759s
+user 2m11,119s
+sys 0m2,841s
+```
--
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