I have a C ++ project with many goals that include a lot of boost header files and other heavy stream headers. Most goals include the same headings. So I thought this might be ideal for using precompiled headers (pch). So I created a header file with the most included headers and precompiled it.
This reduced the lines of code of the compilation module from 350k to 120k (I passed the flag -save-tempsto gcc to check this). I checked that it was used with a parameter -H, and pch has an exclamation mark in front of it. The precompiled header has 550 MB.
Although the compilation time was reduced from only 23 seconds to 20 seconds.
Can this small improvement be expected from precompiled headers? If not, what am I doing wrong? What is the compilation speed with precompiled headers?
Edit: This is the gcc command:
/ USR / bin / c ++
-fPIC -I / projectDir / build / source -I / projectDir / source -I / usr / include / eigen3 -include / projectDir / build / source / Core / core / cotire / Core_ORIGINAL_CXX_prefix.hxx -Winvalid -pch -g -Wall -Wextra -Wno-long-long -Wno-unused-parameter -std = C ++ 0x -DBOOST_ENABLE_ASSERT_HANDLER -D_REENTRANT -o CMakeFiles / SubProject.dir / cotire / SubProject_ORIGINAL_CXX_unity.cxxDo /build/source/ArmarXCore/statechart/cotire/SubProject_ORIGINAL_CXX_unity.cxx
The transfer result -ftime-reportgives me (with PCH enabled):
Execution times (seconds)
phase setup : 0.00 ( 0%) usr 0.00 ( 0%) sys 0.01 ( 0%) wall 1321 kB ( 0%) ggc
phase parsing : 7.29 (32%) usr 1.69 (51%) sys 8.99 (35%) wall 1135793 kB (54%) ggc
phase lang. deferred : 2.75 (12%) usr 0.40 (12%) sys 3.15 (12%) wall 317920 kB (15%) ggc
phase opt and generate : 12.03 (53%) usr 1.17 (36%) sys 13.22 (51%) wall 622545 kB (30%) ggc
phase check & debug info: 0.01 ( 0%) usr 0.00 ( 0%) sys 0.00 ( 0%) wall 440 kB ( 0%) ggc
phase last asm : 0.63 ( 3%) usr 0.02 ( 1%) sys 0.64 ( 2%) wall 26440 kB ( 1%) ggc
phase finalize : 0.00 ( 0%) usr 0.01 ( 0%) sys 0.02 ( 0%) wall 0 kB ( 0%) ggc
|name lookup : 1.30 ( 6%) usr 0.29 ( 9%) sys 1.42 ( 5%) wall 153617 kB ( 7%) ggc
|overload resolution : 3.37 (15%) usr 0.59 (18%) sys 3.30 (13%) wall 360551 kB (17%) ggc
garbage collection : 1.80 ( 8%) usr 0.01 ( 0%) sys 1.82 ( 7%) wall 0 kB ( 0%) ggc
dump files : 0.11 ( 0%) usr 0.05 ( 2%) sys 0.18 ( 1%) wall 0 kB ( 0%) ggc
callgraph construction : 0.44 ( 2%) usr 0.10 ( 3%) sys 0.59 ( 2%) wall 26388 kB ( 1%) ggc
callgraph optimization : 0.21 ( 1%) usr 0.11 ( 3%) sys 0.23 ( 1%) wall 16131 kB ( 1%) ggc
ipa free inline summary : 0.01 ( 0%) usr 0.00 ( 0%) sys 0.01 ( 0%) wall 0 kB ( 0%) ggc
cfg construction : 0.03 ( 0%) usr 0.00 ( 0%) sys 0.03 ( 0%) wall 2119 kB ( 0%) ggc
cfg cleanup : 0.08 ( 0%) usr 0.00 ( 0%) sys 0.11 ( 0%) wall 169 kB ( 0%) ggc
trivially dead code : 0.05 ( 0%) usr 0.02 ( 1%) sys 0.13 ( 0%) wall 0 kB ( 0%) ggc
df scan insns : 0.30 ( 1%) usr 0.02 ( 1%) sys 0.38 ( 1%) wall 1126 kB ( 0%) ggc
df live regs : 0.07 ( 0%) usr 0.00 ( 0%) sys 0.10 ( 0%) wall 0 kB ( 0%) ggc
df reg dead/unused notes: 0.10 ( 0%) usr 0.03 ( 1%) sys 0.12 ( 0%) wall 7774 kB ( 0%) ggc
register information : 0.03 ( 0%) usr 0.00 ( 0%) sys 0.04 ( 0%) wall 0 kB ( 0%) ggc
alias analysis : 0.02 ( 0%) usr 0.02 ( 1%) sys 0.08 ( 0%) wall 2621 kB ( 0%) ggc
rebuild jump labels : 0.05 ( 0%) usr 0.01 ( 0%) sys 0.03 ( 0%) wall 0 kB ( 0%) ggc
preprocessing : 1.16 ( 5%) usr 0.45 (14%) sys 1.61 ( 6%) wall 209848 kB (10%) ggc
parser (global) : 0.43 ( 2%) usr 0.29 ( 9%) sys 0.83 ( 3%) wall 193966 kB ( 9%) ggc
parser struct body : 1.03 ( 5%) usr 0.20 ( 6%) sys 1.37 ( 5%) wall 199825 kB ( 9%) ggc
parser enumerator list : 0.01 ( 0%) usr 0.00 ( 0%) sys 0.00 ( 0%) wall 574 kB ( 0%) ggc
parser function body : 0.53 ( 2%) usr 0.06 ( 2%) sys 0.49 ( 2%) wall 35252 kB ( 2%) ggc
parser inl. func. body : 0.13 ( 1%) usr 0.03 ( 1%) sys 0.14 ( 1%) wall 11720 kB ( 1%) ggc
parser inl. meth. body : 1.14 ( 5%) usr 0.19 ( 6%) sys 1.45 ( 6%) wall 115776 kB ( 6%) ggc
template instantiation : 4.11 (18%) usr 0.82 (25%) sys 4.78 (18%) wall 566245 kB (27%) ggc
inline parameters : 0.05 ( 0%) usr 0.01 ( 0%) sys 0.03 ( 0%) wall 12792 kB ( 1%) ggc
tree gimplify : 0.28 ( 1%) usr 0.03 ( 1%) sys 0.27 ( 1%) wall 55239 kB ( 3%) ggc
tree eh : 0.19 ( 1%) usr 0.00 ( 0%) sys 0.14 ( 1%) wall 20091 kB ( 1%) ggc
tree CFG construction : 0.02 ( 0%) usr 0.00 ( 0%) sys 0.05 ( 0%) wall 34452 kB ( 2%) ggc
tree CFG cleanup : 0.09 ( 0%) usr 0.02 ( 1%) sys 0.15 ( 1%) wall 27 kB ( 0%) ggc
tree PHI insertion : 0.01 ( 0%) usr 0.01 ( 0%) sys 0.01 ( 0%) wall 5960 kB ( 0%) ggc
tree SSA rewrite : 0.01 ( 0%) usr 0.00 ( 0%) sys 0.04 ( 0%) wall 8035 kB ( 0%) ggc
tree SSA other : 0.04 ( 0%) usr 0.03 ( 1%) sys 0.12 ( 0%) wall 1604 kB ( 0%) ggc
tree operand scan : 0.06 ( 0%) usr 0.04 ( 1%) sys 0.08 ( 0%) wall 16681 kB ( 1%) ggc
dominance frontiers : 0.00 ( 0%) usr 0.00 ( 0%) sys 0.01 ( 0%) wall 0 kB ( 0%) ggc
dominance computation : 0.14 ( 1%) usr 0.04 ( 1%) sys 0.12 ( 0%) wall 0 kB ( 0%) ggc
out of ssa : 0.04 ( 0%) usr 0.03 ( 1%) sys 0.14 ( 1%) wall 8 kB ( 0%) ggc
expand vars : 0.10 ( 0%) usr 0.00 ( 0%) sys 0.14 ( 1%) wall 10387 kB ( 0%) ggc
expand : 0.79 ( 3%) usr 0.05 ( 2%) sys 0.77 ( 3%) wall 89756 kB ( 4%) ggc
post expand cleanups : 0.10 ( 0%) usr 0.00 ( 0%) sys 0.05 ( 0%) wall 14796 kB ( 1%) ggc
varconst : 0.03 ( 0%) usr 0.00 ( 0%) sys 0.03 ( 0%) wall 532 kB ( 0%) ggc
jump : 0.00 ( 0%) usr 0.01 ( 0%) sys 0.00 ( 0%) wall 0 kB ( 0%) ggc
integrated RA : 4.92 (22%) usr 0.12 ( 4%) sys 4.54 (17%) wall 167029 kB ( 8%) ggc
LRA non-specific : 0.38 ( 2%) usr 0.01 ( 0%) sys 0.81 ( 3%) wall 776 kB ( 0%) ggc
LRA virtuals elimination: 0.07 ( 0%) usr 0.00 ( 0%) sys 0.07 ( 0%) wall 6530 kB ( 0%) ggc
LRA reload inheritance : 0.01 ( 0%) usr 0.00 ( 0%) sys 0.00 ( 0%) wall 4 kB ( 0%) ggc
LRA create live ranges : 0.03 ( 0%) usr 0.00 ( 0%) sys 0.02 ( 0%) wall 40 kB ( 0%) ggc
LRA hard reg assignment : 0.00 ( 0%) usr 0.00 ( 0%) sys 0.01 ( 0%) wall 0 kB ( 0%) ggc
reload : 0.01 ( 0%) usr 0.00 ( 0%) sys 0.03 ( 0%) wall 0 kB ( 0%) ggc
thread pro- & epilogue : 0.16 ( 1%) usr 0.01 ( 0%) sys 0.26 ( 1%) wall 19997 kB ( 1%) ggc
shorten branches : 0.17 ( 1%) usr 0.01 ( 0%) sys 0.16 ( 1%) wall 0 kB ( 0%) ggc
reg stack : 0.01 ( 0%) usr 0.00 ( 0%) sys 0.00 ( 0%) wall 0 kB ( 0%) ggc
final : 0.63 ( 3%) usr 0.04 ( 1%) sys 0.69 ( 3%) wall 29353 kB ( 1%) ggc
symout : 1.28 ( 6%) usr 0.06 ( 2%) sys 1.23 ( 5%) wall 173563 kB ( 8%) ggc
uninit var analysis : 0.00 ( 0%) usr 0.00 ( 0%) sys 0.01 ( 0%) wall 0 kB ( 0%) ggc
rest of compilation : 0.81 ( 4%) usr 0.18 ( 5%) sys 0.93 ( 4%) wall 34415 kB ( 2%) ggc
unaccounted todo : 0.25 ( 1%) usr 0.16 ( 5%) sys 0.39 ( 1%) wall 0 kB ( 0%) ggc
TOTAL : 22.71 3.29 26.03 2104543 kB
thanks veio