• bioinfornatics (9/9) Mar 07 2013 Dear,
• bearophile (15/16) Mar 07 2013 To be sure of what's faster you often have to write small
• lomereiter (15/24) Mar 07 2013 The second is probably faster (with optimizations enabled),
• bioinfornatics (3/35) Mar 07 2013 and if is not stdout but File ?
• bioinfornatics (7/47) Mar 07 2013 I only replace write by put and do this:
• lomereiter (5/11) Mar 07 2013 Indeed, that shouldn't be the case. I filed a bug request:

"bioinfornatics" <bioinfornatics fedoraproject.org> writes:

Dear,

little question when writing to a file 5 "hello" lines (by 
example)
I would like to know if they are a difference between:

writeln( "hello" ); x5

and:

string[] helloList = [ "hello","hello","hello","hello","hello"];
writeln( helloList.join( newline) );


I mean if one way is more efficient by speed?

"bearophile" <bearophileHUGS lycos.com> writes:

bioinfornatics:

 I mean if one way is more efficient by speed?

To be sure of what's faster you often have to write small 
benchmarks.

In this case this should be good:

import std.stdio, std.array;
void main() {
     writefln("%-(%s\n%)", ["hello"].replicate(5));
}


But if you want speed this is is probably faster:

import core.stdc.stdio: puts;
void main() {
     puts("hello\nhello\nhello\nhello\nhello");
}

Bye,
bearophile

"lomereiter" <lomereiter gmail.com> writes:

The second is probably faster (with optimizations enabled), 
because each call to writeln incurs overhead of locking/unlocking 
the file stream (which is stdout in this case).

If you need to print huge amounts of data, use lockingTextWriter 
like this:

auto w = stdout.lockingTextWriter;
foreach (i; 0 .. 5) {
     w.put("sometext\n");
     w.formattedwrite("%d\n", some_number);
}

However, std.format.formattedWrite is also relatively slow, so 
it's better to prepare string representation of an object in a 
buffer on the stack - say, with snprintf, or your own set of 
formatting functions - and then put it into the writer.

On Thursday, 7 March 2013 at 10:04:34 UTC, bioinfornatics wrote:
 Dear,

 little question when writing to a file 5 "hello" lines (by 
 example)
 I would like to know if they are a difference between:

 writeln( "hello" ); x5

 and:

 string[] helloList = [ "hello","hello","hello","hello","hello"];
 writeln( helloList.join( newline) );


 I mean if one way is more efficient by speed?

"bioinfornatics" <bioinfornatics fedoraproject.org> writes:

On Thursday, 7 March 2013 at 13:37:56 UTC, lomereiter wrote:
 The second is probably faster (with optimizations enabled), 
 because each call to writeln incurs overhead of 
 locking/unlocking the file stream (which is stdout in this 
 case).

 If you need to print huge amounts of data, use 
 lockingTextWriter like this:

 auto w = stdout.lockingTextWriter;
 foreach (i; 0 .. 5) {
     w.put("sometext\n");
     w.formattedwrite("%d\n", some_number);
 }

 However, std.format.formattedWrite is also relatively slow, so 
 it's better to prepare string representation of an object in a 
 buffer on the stack - say, with snprintf, or your own set of 
 formatting functions - and then put it into the writer.

 On Thursday, 7 March 2013 at 10:04:34 UTC, bioinfornatics wrote:
 Dear,

 little question when writing to a file 5 "hello" lines (by 
 example)
 I would like to know if they are a difference between:

 writeln( "hello" ); x5

 and:

 string[] helloList = [ 
 "hello","hello","hello","hello","hello"];
 writeln( helloList.join( newline) );


 I mean if one way is more efficient by speed?


and if is not stdout but File ?

thanks a lot that is really interesting

"bioinfornatics" <bioinfornatics fedoraproject.org> writes:

On Thursday, 7 March 2013 at 16:12:09 UTC, bioinfornatics wrote:
 On Thursday, 7 March 2013 at 13:37:56 UTC, lomereiter wrote:
 The second is probably faster (with optimizations enabled), 
 because each call to writeln incurs overhead of 
 locking/unlocking the file stream (which is stdout in this 
 case).

 If you need to print huge amounts of data, use 
 lockingTextWriter like this:

 auto w = stdout.lockingTextWriter;
 foreach (i; 0 .. 5) {
    w.put("sometext\n");
    w.formattedwrite("%d\n", some_number);
 }

 However, std.format.formattedWrite is also relatively slow, so 
 it's better to prepare string representation of an object in a 
 buffer on the stack - say, with snprintf, or your own set of 
 formatting functions - and then put it into the writer.

 On Thursday, 7 March 2013 at 10:04:34 UTC, bioinfornatics 
 wrote:
 Dear,

 little question when writing to a file 5 "hello" lines (by 
 example)
 I would like to know if they are a difference between:

 writeln( "hello" ); x5

 and:

 string[] helloList = [ 
 "hello","hello","hello","hello","hello"];
 writeln( helloList.join( newline) );


 I mean if one way is more efficient by speed?


 and if is not stdout but File ?

 thanks a lot that is really interesting

I only replace write by put and do this:
auto output = File( f.absolutePath().expandTilde(), "w" 
).lockingTextWriter();


that build without get an error but at runtime i got:
std.exception.ErrnoException /env/export/nfs2/cns_prog/opt/gdc/include/d/4.7.
/std/stdio.d(1267): 
  (Bad file descriptor)

"lomereiter" <lomereiter gmail.com> writes:

Indeed, that shouldn't be the case. I filed a bug request:

http://d.puremagic.com/issues/show_bug.cgi?id=9661

While it isn't fixed, assign file to a variable so that it 
doesn't go out of scope.

On Thursday, 7 March 2013 at 16:20:24 UTC, bioinfornatics wrote:
 I only replace write by put and do this:
 auto output = File( f.absolutePath().expandTilde(), "w" 
 ).lockingTextWriter();


 that build without get an error but at runtime i got:
 std.exception.ErrnoException /env/export/nfs2/cns_prog/opt/gdc/include/d/4.7.2/std/stdio.d(1267):
  (Bad file descriptor)