StringBuilder question

[Jerry]

Assuming we've defined StringBuilder myBuilder, which of the following is most expensive:

//scenario 1
myBuilder.Appen d("test" + "test" + "test");

//scenario 2
myBuilder.Appen d("test");
myBuilder.Appen d("test");
myBuilder.Appen d("test");

[Shakir Hussain]

Re: StringBuilder question

Jerry,

you mean more number of lines as expensive? or the performance?

I would say the correct way to do that may be

myBuilder.Appen d("test").Appen d("test1").Appe nd("test2");

Shak.


"Jerry" <Jerry@discussi ons.microsoft.c om> wrote in message
news:24BF3B72-7A07-492F-A0CD-9561CBA4A289@mi crosoft.com...[color=blue]
> Assuming we've defined StringBuilder myBuilder, which of the following is[/color]
most expensive:[color=blue]
>
> //scenario 1
> myBuilder.Appen d("test" + "test" + "test");
>
> //scenario 2
> myBuilder.Appen d("test");
> myBuilder.Appen d("test");
> myBuilder.Appen d("test");[/color]

[John Wood]

Re: StringBuilder question

scenario 1, because a new copy of the string is being created for each +
operation (which is why there is a StringBuilder class in the first place).

However, it's possible (because of constant folding) that may actually
compile to be myBuilding.Appe nd("testtesttes t");, in which case the second
scenario would be more expensive.

--
John Wood
EMail: first name, dot, last name, at priorganize.com

"Jerry" <Jerry@discussi ons.microsoft.c om> wrote in message
news:24BF3B72-7A07-492F-A0CD-9561CBA4A289@mi crosoft.com...[color=blue]
> Assuming we've defined StringBuilder myBuilder, which of the following is[/color]
most expensive:[color=blue]
>
> //scenario 1
> myBuilder.Appen d("test" + "test" + "test");
>
> //scenario 2
> myBuilder.Appen d("test");
> myBuilder.Appen d("test");
> myBuilder.Appen d("test");[/color]

[Daniel Billingsley]

Re: StringBuilder question

And of course, both are more expensive than

someString = "test" + "test" + "test";

in both lines of code and performance.

"John Wood" <j@ro.com> wrote in message
news:eyuv3kVWEH A.2928@tk2msftn gp13.phx.gbl...[color=blue]
> scenario 1, because a new copy of the string is being created for each +
> operation (which is why there is a StringBuilder class in the first[/color]
place).[color=blue]
>
> However, it's possible (because of constant folding) that may actually
> compile to be myBuilding.Appe nd("testtesttes t");, in which case the second
> scenario would be more expensive.
>
> --
> John Wood
> EMail: first name, dot, last name, at priorganize.com
>
> "Jerry" <Jerry@discussi ons.microsoft.c om> wrote in message
> news:24BF3B72-7A07-492F-A0CD-9561CBA4A289@mi crosoft.com...[color=green]
> > Assuming we've defined StringBuilder myBuilder, which of the following[/color][/color]
is[color=blue]
> most expensive:[color=green]
> >
> > //scenario 1
> > myBuilder.Appen d("test" + "test" + "test");
> >
> > //scenario 2
> > myBuilder.Appen d("test");
> > myBuilder.Appen d("test");
> > myBuilder.Appen d("test");[/color]
>
>[/color]

[John Wood]

Re: StringBuilder question

Right. If it does implement constant folding for literal strings that may
just become an assignment of the interned string "testtestte st" (which will
just be a object handle) to a string reference variable... like 1 IL
instruction.

--
John Wood
EMail: first name, dot, last name, at priorganize.com
"Daniel Billingsley" <dbillingsley@N O_durcon_SPAAMM .com> wrote in message
news:%23yQCUwVW EHA.1764@TK2MSF TNGP10.phx.gbl. ..[color=blue]
> And of course, both are more expensive than
>
> someString = "test" + "test" + "test";
>
> in both lines of code and performance.
>
> "John Wood" <j@ro.com> wrote in message
> news:eyuv3kVWEH A.2928@tk2msftn gp13.phx.gbl...[color=green]
> > scenario 1, because a new copy of the string is being created for each +
> > operation (which is why there is a StringBuilder class in the first[/color]
> place).[color=green]
> >
> > However, it's possible (because of constant folding) that may actually
> > compile to be myBuilding.Appe nd("testtesttes t");, in which case the[/color][/color]
second[color=blue][color=green]
> > scenario would be more expensive.
> >
> > --
> > John Wood
> > EMail: first name, dot, last name, at priorganize.com
> >
> > "Jerry" <Jerry@discussi ons.microsoft.c om> wrote in message
> > news:24BF3B72-7A07-492F-A0CD-9561CBA4A289@mi crosoft.com...[color=darkred]
> > > Assuming we've defined StringBuilder myBuilder, which of the following[/color][/color]
> is[color=green]
> > most expensive:[color=darkred]
> > >
> > > //scenario 1
> > > myBuilder.Appen d("test" + "test" + "test");
> > >
> > > //scenario 2
> > > myBuilder.Appen d("test");
> > > myBuilder.Appen d("test");
> > > myBuilder.Appen d("test");[/color]
> >
> >[/color]
>
>[/color]

[Jerry]

Re: StringBuilder question

RE: And of course, both are more expensive than someString = "test" + "test" + "test"

Let's change this scenario. Pretend there is a string variable named example. Now, which is more expensive in terms of performance & memory alloc.

//scenario 1
myBuilder.Appen d("test" + example + "test");

//scenario 2
myBuilder.Appen d("test");
myBuilder.Appen d(example);
myBuilder.Appen d("test");

//scenario 3
string myString = "test" + example + "test";


Jerry

"John Wood" wrote:
[color=blue]
> Right. If it does implement constant folding for literal strings that may
> just become an assignment of the interned string "testtestte st" (which will
> just be a object handle) to a string reference variable... like 1 IL
> instruction.
>
> --
> John Wood
> EMail: first name, dot, last name, at priorganize.com
> "Daniel Billingsley" <dbillingsley@N O_durcon_SPAAMM .com> wrote in message
> news:%23yQCUwVW EHA.1764@TK2MSF TNGP10.phx.gbl. ..[color=green]
> > And of course, both are more expensive than
> >
> > someString = "test" + "test" + "test";
> >
> > in both lines of code and performance.
> >
> > "John Wood" <j@ro.com> wrote in message
> > news:eyuv3kVWEH A.2928@tk2msftn gp13.phx.gbl...[color=darkred]
> > > scenario 1, because a new copy of the string is being created for each +
> > > operation (which is why there is a StringBuilder class in the first[/color]
> > place).[color=darkred]
> > >
> > > However, it's possible (because of constant folding) that may actually
> > > compile to be myBuilding.Appe nd("testtesttes t");, in which case the[/color][/color]
> second[color=green][color=darkred]
> > > scenario would be more expensive.
> > >
> > > --
> > > John Wood
> > > EMail: first name, dot, last name, at priorganize.com
> > >
> > > "Jerry" <Jerry@discussi ons.microsoft.c om> wrote in message
> > > news:24BF3B72-7A07-492F-A0CD-9561CBA4A289@mi crosoft.com...
> > > > Assuming we've defined StringBuilder myBuilder, which of the following[/color]
> > is[color=darkred]
> > > most expensive:
> > > >
> > > > //scenario 1
> > > > myBuilder.Appen d("test" + "test" + "test");
> > > >
> > > > //scenario 2
> > > > myBuilder.Appen d("test");
> > > > myBuilder.Appen d("test");
> > > > myBuilder.Appen d("test");
> > >
> > >[/color]
> >
> >[/color]
>
>
>[/color]

[John Wood]

Re: StringBuilder question

scenario1 probably more expensive because of the memory copying that's going
on.

Depending on the size of the string in 'example', scenario2 would probably
be the fastest.

--
John Wood
EMail: first name, dot, last name, at priorganize.com

"Jerry" <Jerry@discussi ons.microsoft.c om> wrote in message
news:4A110FA8-27CE-48EF-95B4-5FE4AE12F788@mi crosoft.com...[color=blue]
> RE: And of course, both are more expensive than someString = "test" +[/color]
"test" + "test"[color=blue]
>
> Let's change this scenario. Pretend there is a string variable named[/color]
example. Now, which is more expensive in terms of performance & memory
alloc.[color=blue]
>
> //scenario 1
> myBuilder.Appen d("test" + example + "test");
>
> //scenario 2
> myBuilder.Appen d("test");
> myBuilder.Appen d(example);
> myBuilder.Appen d("test");
>
> //scenario 3
> string myString = "test" + example + "test";
>
>
> Jerry
>
> "John Wood" wrote:
>[color=green]
> > Right. If it does implement constant folding for literal strings that[/color][/color]
may[color=blue][color=green]
> > just become an assignment of the interned string "testtestte st" (which[/color][/color]
will[color=blue][color=green]
> > just be a object handle) to a string reference variable... like 1 IL
> > instruction.
> >
> > --
> > John Wood
> > EMail: first name, dot, last name, at priorganize.com
> > "Daniel Billingsley" <dbillingsley@N O_durcon_SPAAMM .com> wrote in[/color][/color]
message[color=blue][color=green]
> > news:%23yQCUwVW EHA.1764@TK2MSF TNGP10.phx.gbl. ..[color=darkred]
> > > And of course, both are more expensive than
> > >
> > > someString = "test" + "test" + "test";
> > >
> > > in both lines of code and performance.
> > >
> > > "John Wood" <j@ro.com> wrote in message
> > > news:eyuv3kVWEH A.2928@tk2msftn gp13.phx.gbl...
> > > > scenario 1, because a new copy of the string is being created for[/color][/color][/color]
each +[color=blue][color=green][color=darkred]
> > > > operation (which is why there is a StringBuilder class in the first
> > > place).
> > > >
> > > > However, it's possible (because of constant folding) that may[/color][/color][/color]
actually[color=blue][color=green][color=darkred]
> > > > compile to be myBuilding.Appe nd("testtesttes t");, in which case the[/color]
> > second[color=darkred]
> > > > scenario would be more expensive.
> > > >
> > > > --
> > > > John Wood
> > > > EMail: first name, dot, last name, at priorganize.com
> > > >
> > > > "Jerry" <Jerry@discussi ons.microsoft.c om> wrote in message
> > > > news:24BF3B72-7A07-492F-A0CD-9561CBA4A289@mi crosoft.com...
> > > > > Assuming we've defined StringBuilder myBuilder, which of the[/color][/color][/color]
following[color=blue][color=green][color=darkred]
> > > is
> > > > most expensive:
> > > > >
> > > > > //scenario 1
> > > > > myBuilder.Appen d("test" + "test" + "test");
> > > > >
> > > > > //scenario 2
> > > > > myBuilder.Appen d("test");
> > > > > myBuilder.Appen d("test");
> > > > > myBuilder.Appen d("test");
> > > >
> > > >
> > >
> > >[/color]
> >
> >
> >[/color][/color]

[Jon Skeet [C# MVP]]

Re: StringBuilder question

Jerry <Jerry@discussi ons.microsoft.c om> wrote:[color=blue]
> RE: And of course, both are more expensive than someString = "test" + "test" + "test"
>
> Let's change this scenario. Pretend there is a string variable named
> example. Now, which is more expensive in terms of performance &
> memory alloc.
>
> //scenario 1
> myBuilder.Appen d("test" + example + "test");
>
> //scenario 2
> myBuilder.Appen d("test");
> myBuilder.Appen d(example);
> myBuilder.Appen d("test");
>
> //scenario 3
> string myString = "test" + example + "test";[/color]

Scenario 3 is the cheapest: it involves a single call to String.Concat,
which is able to work out the total length of the string, allocate the
appropriate memory, and then copy the 3 strings in place.

--
Jon Skeet - <skeet@pobox.co m>

http://www.pobox.com/~skeet

If replying to the group, please do not mail me too

[J.Marsch]

Re: StringBuilder question

According to Rico Mariani (MS performance guru), it depends. It sounds like
something like:
someString = "test" + "test" + "test";
only counts as one concatenation, so it's not really worth a StringBuilder.

Some interesting info here:

http://weblogs.asp.net/ricom/archive/2003/12/02/40778.aspx

and here:

http://weblogs.asp.net/ricom/archive/2003/12/15/43628.aspx

"Jerry" <Jerry@discussi ons.microsoft.c om> wrote in message
news:4A110FA8-27CE-48EF-95B4-5FE4AE12F788@mi crosoft.com...[color=blue]
> RE: And of course, both are more expensive than someString = "test" +[/color]
"test" + "test"[color=blue]
>
> Let's change this scenario. Pretend there is a string variable named[/color]
example. Now, which is more expensive in terms of performance & memory
alloc.[color=blue]
>
> //scenario 1
> myBuilder.Appen d("test" + example + "test");
>
> //scenario 2
> myBuilder.Appen d("test");
> myBuilder.Appen d(example);
> myBuilder.Appen d("test");
>
> //scenario 3
> string myString = "test" + example + "test";
>
>
> Jerry
>
> "John Wood" wrote:
>[color=green]
> > Right. If it does implement constant folding for literal strings that[/color][/color]
may[color=blue][color=green]
> > just become an assignment of the interned string "testtestte st" (which[/color][/color]
will[color=blue][color=green]
> > just be a object handle) to a string reference variable... like 1 IL
> > instruction.
> >
> > --
> > John Wood
> > EMail: first name, dot, last name, at priorganize.com
> > "Daniel Billingsley" <dbillingsley@N O_durcon_SPAAMM .com> wrote in[/color][/color]
message[color=blue][color=green]
> > news:%23yQCUwVW EHA.1764@TK2MSF TNGP10.phx.gbl. ..[color=darkred]
> > > And of course, both are more expensive than
> > >
> > > someString = "test" + "test" + "test";
> > >
> > > in both lines of code and performance.
> > >
> > > "John Wood" <j@ro.com> wrote in message
> > > news:eyuv3kVWEH A.2928@tk2msftn gp13.phx.gbl...
> > > > scenario 1, because a new copy of the string is being created for[/color][/color][/color]
each +[color=blue][color=green][color=darkred]
> > > > operation (which is why there is a StringBuilder class in the first
> > > place).
> > > >
> > > > However, it's possible (because of constant folding) that may[/color][/color][/color]
actually[color=blue][color=green][color=darkred]
> > > > compile to be myBuilding.Appe nd("testtesttes t");, in which case the[/color]
> > second[color=darkred]
> > > > scenario would be more expensive.
> > > >
> > > > --
> > > > John Wood
> > > > EMail: first name, dot, last name, at priorganize.com
> > > >
> > > > "Jerry" <Jerry@discussi ons.microsoft.c om> wrote in message
> > > > news:24BF3B72-7A07-492F-A0CD-9561CBA4A289@mi crosoft.com...
> > > > > Assuming we've defined StringBuilder myBuilder, which of the[/color][/color][/color]
following[color=blue][color=green][color=darkred]
> > > is
> > > > most expensive:
> > > > >
> > > > > //scenario 1
> > > > > myBuilder.Appen d("test" + "test" + "test");
> > > > >
> > > > > //scenario 2
> > > > > myBuilder.Appen d("test");
> > > > > myBuilder.Appen d("test");
> > > > > myBuilder.Appen d("test");
> > > >
> > > >
> > >
> > >[/color]
> >
> >
> >[/color][/color]

[Jerry]

Re: StringBuilder question

So what the hey is StringBuilder for? Can someone provide an example where using StringBuilder will be less expensive than an approach using string concatenation?

"Jon Skeet [C# MVP]" wrote:
[color=blue]
> Jerry <Jerry@discussi ons.microsoft.c om> wrote:[color=green]
> > RE: And of course, both are more expensive than someString = "test" + "test" + "test"
> >
> > Let's change this scenario. Pretend there is a string variable named
> > example. Now, which is more expensive in terms of performance &
> > memory alloc.
> >
> > //scenario 1
> > myBuilder.Appen d("test" + example + "test");
> >
> > //scenario 2
> > myBuilder.Appen d("test");
> > myBuilder.Appen d(example);
> > myBuilder.Appen d("test");
> >
> > //scenario 3
> > string myString = "test" + example + "test";[/color]
>
> Scenario 3 is the cheapest: it involves a single call to String.Concat,
> which is able to work out the total length of the string, allocate the
> appropriate memory, and then copy the 3 strings in place.
>
> --
> Jon Skeet - <skeet@pobox.co m>
> http://www.pobox.com/~skeet
> If replying to the group, please do not mail me too
>[/color]

[Daniel Billingsley]

Re: StringBuilder question

Yep, the third is still faster. Even doing it like
string myString = "test";
myString += example;
myString += "test";

it would still be faster than the corresponding StringBuilder (if you
include the required .ToString() ) in this specific example.

Keep in mind, even though this is a pet topic of mine, that we're talking
microseconds of difference for a single call so it's almost always better to
just write the code that looks the cleanest. I would consider that to be #3
in your specific example, but with a bit more complexity of the strings
being concatenated I would use string.Format() for that reason, even though
it is considerably slower than all these alternatives.

"Jon Skeet [C# MVP]" <skeet@pobox.co m> wrote in message
news:MPG.1b43f9 0dd7d3106d98ad7 c@msnews.micros oft.com...[color=blue]
> Jerry <Jerry@discussi ons.microsoft.c om> wrote:[color=green]
> > RE: And of course, both are more expensive than someString = "test" +[/color][/color]
"test" + "test"[color=blue][color=green]
> >
> > Let's change this scenario. Pretend there is a string variable named
> > example. Now, which is more expensive in terms of performance &
> > memory alloc.
> >
> > //scenario 1
> > myBuilder.Appen d("test" + example + "test");
> >
> > //scenario 2
> > myBuilder.Appen d("test");
> > myBuilder.Appen d(example);
> > myBuilder.Appen d("test");
> >
> > //scenario 3
> > string myString = "test" + example + "test";[/color]
>
> Scenario 3 is the cheapest: it involves a single call to String.Concat,
> which is able to work out the total length of the string, allocate the
> appropriate memory, and then copy the 3 strings in place.
>
> --
> Jon Skeet - <skeet@pobox.co m>
> http://www.pobox.com/~skeet
> If replying to the group, please do not mail me too[/color]

[Jon Skeet [C# MVP]]

Re: StringBuilder question

Jerry <Jerry@discussi ons.microsoft.c om> wrote:[color=blue]
> So what the hey is StringBuilder for? Can someone provide an example
> where using StringBuilder will be less expensive than an approach
> using string concatenation?[/color]

Sure - any time you don't have all the information in some static way
to start with. For instance:

StringBuilder builder = new StringBuilder() ;
using (StreamReader reader = ...)
{
string line;
while ( (line=reader.Re adLine()) != null)
{
string word = ProcessLineSome how();
builder.Append( word);
}
}

--
Jon Skeet - <skeet@pobox.co m>

http://www.pobox.com/~skeet

If replying to the group, please do not mail me too

[Jon Skeet [C# MVP]]

Re: StringBuilder question

J.Marsch <jeremy@ctcdeve loper.com> wrote:[color=blue]
> According to Rico Mariani (MS performance guru), it depends. It sounds like
> something like:
> someString = "test" + "test" + "test";
> only counts as one concatenation, so it's not really worth a StringBuilder.
>
> Some interesting info here:
> http://weblogs.asp.net/ricom/archive.../02/40778.aspx
>
> and here:
> http://weblogs.asp.net/ricom/archive.../15/43628.aspx[/color]

While I haven't been able to find where it's documented, I believe the
above actually doesn't count as *any* concatenations - it compiles to
the same code as

someString = "testtestte st";

--
Jon Skeet - <skeet@pobox.co m>

http://www.pobox.com/~skeet

If replying to the group, please do not mail me too

[John Wood]

Re: StringBuilder question

I just tested this... it does. (compiles to ldstr "testtestte st")
Plus I saw constant folding listed as one of the JIT's optimization
features.

--
John Wood
EMail: first name, dot, last name, at priorganize.com
"Jon Skeet [C# MVP]" <skeet@pobox.co m> wrote in message
news:MPG.1b4401 60136d578698ad7 e@msnews.micros oft.com...[color=blue]
> J.Marsch <jeremy@ctcdeve loper.com> wrote:[color=green]
> > According to Rico Mariani (MS performance guru), it depends. It sounds[/color][/color]
like[color=blue][color=green]
> > something like:
> > someString = "test" + "test" + "test";
> > only counts as one concatenation, so it's not really worth a[/color][/color]
StringBuilder.[color=blue][color=green]
> >
> > Some interesting info here:
> > http://weblogs.asp.net/ricom/archive.../02/40778.aspx
> >
> > and here:
> > http://weblogs.asp.net/ricom/archive.../15/43628.aspx[/color]
>
> While I haven't been able to find where it's documented, I believe the
> above actually doesn't count as *any* concatenations - it compiles to
> the same code as
>
> someString = "testtestte st";
>
> --
> Jon Skeet - <skeet@pobox.co m>
> http://www.pobox.com/~skeet
> If replying to the group, please do not mail me too[/color]

[John Wood]

Re: StringBuilder question

It's also worth noting that Concat has the following overloads:

string, string
string, string, string
string, string, string, string
string[]

So if your expression has more than four +s... it'll do quite a bit more
work (constructing an array and putting each item into the array before
calling).

Although this is probably still considerably less work than what
stringbuilder would do.

--
John Wood
EMail: first name, dot, last name, at priorganize.com
"Jon Skeet [C# MVP]" <skeet@pobox.co m> wrote in message
news:MPG.1b4401 60136d578698ad7 e@msnews.micros oft.com...[color=blue]
> J.Marsch <jeremy@ctcdeve loper.com> wrote:[color=green]
> > According to Rico Mariani (MS performance guru), it depends. It sounds[/color][/color]
like[color=blue][color=green]
> > something like:
> > someString = "test" + "test" + "test";
> > only counts as one concatenation, so it's not really worth a[/color][/color]
StringBuilder.[color=blue][color=green]
> >
> > Some interesting info here:
> > http://weblogs.asp.net/ricom/archive.../02/40778.aspx
> >
> > and here:
> > http://weblogs.asp.net/ricom/archive.../15/43628.aspx[/color]
>
> While I haven't been able to find where it's documented, I believe the
> above actually doesn't count as *any* concatenations - it compiles to
> the same code as
>
> someString = "testtestte st";
>
> --
> Jon Skeet - <skeet@pobox.co m>
> http://www.pobox.com/~skeet
> If replying to the group, please do not mail me too[/color]