Bad news from the Ivory Tower, part III.
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#!/bin/bash
n=100 # number of classes
m=10000000 # number of cycles
cc=/usr/bin/g++
function useit() {
time for i in $s ; do $cc -c $i.cpp ; done
echo ".cpp: `cat *.cpp | wc -c`"
echo ".o: `cat *.o | wc -c`"
echo "
#include \"1.h\"
int main() {
int s = 0;
X1 x;
for (int i = $m; --i >= 0;)
s += x.clone()->x();
return s;
}
" > main.cpp
$cc -c -O3 main.cpp
$cc main.o 1.o
time ./a.out
echo
}
s=`seq 1 $n`;
rm -rf 1 2
mkdir 1 2
cd 1
echo "struct X { virtual X * clone()=0; virtual int x()=0; };" > 0.h
for i in $s ; do
echo "#include \"0.h\"" > $i.h
echo "struct X$i : X { virtual X * clone(); int x() {return $i;} }; "
>> $i.h
echo "#include \"$i.h\"" > $i.cpp
echo "X * X$i::clone() { return new X$i; }" >> $i.cpp
done
echo
echo "Bald pointers:"
useit
cd ../2
echo "#include <memory>" > 0.h
echo "struct X { virtual std::auto_ptr<X> clone()=0; virtual int x()=0;};" >>
0.h
for i in $s ; do
echo "#include \"0.h\"" > $i.h
echo "struct X$i : X { virtual std::auto_ptr<X> clone(); int x()
{return $i; }}; " >> $i.h
echo "#include \"$i.h\"" > $i.cpp
echo "std::auto_ptr<X> X$i::clone() { return std::auto_ptr<X>(new X$i);
}" >> $i.cpp
done
echo
echo "std::auto_ptr<>:"
useit
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[EMAIL PROTECTED]:/tmp/t1 > ./1.sh
Bald pointers:
real 0m2.998s
user 0m2.224s
sys 0m0.764s
.cpp: 5276
.o: 312308
real 0m1.342s
user 0m1.152s
sys 0m0.184s
std::auto_ptr<>:
real 0m15.354s
user 0m13.461s
sys 0m1.784s
.cpp: 8376
.o: 476308
real 0m1.807s
user 0m1.792s
sys 0m0.012s
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Summary: Using std::auto_ptr<X> instead of X* for cloning costs us
- a factor 5(!) in compile time
- a factor 1.3(!) in run time
[- a factor 1.5 in .cpp size]
[- a factor 1.5 in .o size]
For no good reason. Both (yes there are two!) places where we call
clone() look like
it->inset = it->inset->clone().release();
So it's not much clarity we gain by using std::auto_ptr<> at all.
Andre'
