Re: Slow UDF call?

[H. S. Teoh via Digitalmars-d-learn]

On Sat, Aug 17, 2019 at 09:42:00PM +, Giovanni Di Maria via 
Digitalmars-d-learn wrote:
[...]
> I have also compiled with:
> dmd program.d -O -release -inline -boundscheck=off
> 
> and the execution speed is very very fast.
[...]

If performance is important to you, I recommend checking out LDC. IME,
it consistently produces code that outperforms dmd-generated code by
about 20-30%, sometimes even as high as 40-50%, depending on the nature
of your code.


T

-- 
Never ascribe to malice that which is adequately explained by incompetence. -- 
Napoleon Bonaparte

Re: Slow UDF call?

[Giovanni Di Maria via Digitalmars-d-learn]

On Saturday, 17 August 2019 at 20:57:44 UTC, Giovanni Di Maria 
wrote:

On Saturday, 17 August 2019 at 20:15:02 UTC, Stefan Koch wrote:
On Saturday, 17 August 2019 at 19:43:22 UTC, Giovanni Di Maria 
wrote:

[...]


Yes they do

A function call has a cost.
In case of a function which performes a 1 cycle  (nominally 
without ILP) operation, the overhead of the function call 
dominates.

try compiling with -inline and compare again.





Hi Stefan Koch
Thank you very much.
With the option -inline, now the execution is very fast,
only 4 seconds
Thnak you thank you very much.
Giovanni



I have also compiled with:
dmd program.d -O -release -inline -boundscheck=off

and the execution speed is very very fast.
Giovanni

Re: Slow UDF call?

[Giovanni Di Maria via Digitalmars-d-learn]

On Saturday, 17 August 2019 at 20:15:02 UTC, Stefan Koch wrote:
On Saturday, 17 August 2019 at 19:43:22 UTC, Giovanni Di Maria 
wrote:

[...]


Yes they do

A function call has a cost.
In case of a function which performes a 1 cycle  (nominally 
without ILP) operation, the overhead of the function call 
dominates.

try compiling with -inline and compare again.





Hi Stefan Koch
Thank you very much.
With the option -inline, now the execution is very fast,
only 4 seconds
Thnak you thank you very much.
Giovanni

Re: Slow UDF call?

[Stefan Koch via Digitalmars-d-learn]

On Saturday, 17 August 2019 at 19:43:22 UTC, Giovanni Di Maria 
wrote:

Hi,
i have seen that a simple operation (in a loop) is faster than 
the equivalent UDF.
The first example takes 4 seconds, the second example takes 16 
seconds.

Local variables influence the speed of execution?
Thank you very much.
Giovanni

==

import std.stdio;
void main()
{
int a,b;
int s;
int k;
writeln("START");
for(k=1;k<=2_000_000_000;k++)
{
a=7;
b=20;
s=a+b;
}
writeln("Fine ",k," ",s);
}

==


import std.stdio;
void main()
{
int a,b;
int s;
int k;
writeln("START");
for(k=1;k<=2_000_000_000;k++)
{
a=7;
b=20;
s=somma(a,b);
}
writeln("Fine ",k," ",s);
}

int somma(int n1,int n2)
{
return n1+n2;
}


Yes they do

A function call has a cost.
In case of a function which performes a 1 cycle  (nominally 
without ILP) operation, the overhead of the function call 
dominates.

try compiling with -inline and compare again.

Slow UDF call?

[Giovanni Di Maria via Digitalmars-d-learn]

Hi,
i have seen that a simple operation (in a loop) is faster than 
the equivalent UDF.
The first example takes 4 seconds, the second example takes 16 
seconds.

Local variables influence the speed of execution?
Thank you very much.
Giovanni

==

import std.stdio;
void main()
{
int a,b;
int s;
int k;
writeln("START");
for(k=1;k<=2_000_000_000;k++)
{
a=7;
b=20;
s=a+b;
}
writeln("Fine ",k," ",s);
}

==


import std.stdio;
void main()
{
int a,b;
int s;
int k;
writeln("START");
for(k=1;k<=2_000_000_000;k++)
{
a=7;
b=20;
s=somma(a,b);
}
writeln("Fine ",k," ",s);
}

int somma(int n1,int n2)
{
return n1+n2;
}