AAs of struct or array

[bearophile]

I have noticed a significant speed difference between foo1 and foo2 (D2 code):

import std.c.stdio: printf;

int foo1(int x, int y) {
static int[int[2]] cache;
int[2] args = [x, y];
cache[args] = x;
return x;
}

int foo2(int x, int y) {
static struct Pair { int x, y; }
static int[Pair] cache;
Pair args = Pair(x, y);
cache[args] = x;
return x;
}

void main() {
enum int N = 600;
int tot;
foreach (x; 1 .. N)
foreach (y; 1 .. N)
tot += foo2(x, y); // use foo1 or foo2 here
printf(%d\n, tot);
}


Bye,
bearophile

Re: AAs of struct or array

[Ali Çehreli]

bearophile wrote:

I have noticed a significant speed difference between foo1 and foo2 (D2 code):

import std.c.stdio: printf;

int foo1(int x, int y) {
static int[int[2]] cache;
int[2] args = [x, y];
cache[args] = x;


Most of it comes from the use of that temporary. -O doesn't help either.

This makes foo1 only slightly slower than foo2:

// int[2] args = [x, y];
cache[[x, y]] = x;


return x;
}

int foo2(int x, int y) {
static struct Pair { int x, y; }
static int[Pair] cache;
Pair args = Pair(x, y);
cache[args] = x;
return x;
}

void main() {
enum int N = 600;
int tot;
foreach (x; 1 .. N)
foreach (y; 1 .. N)
tot += foo2(x, y); // use foo1 or foo2 here
printf(%d\n, tot);
}


Bye,
bearophile


Ali

Re: AAs of struct or array

[Pelle]

On 05/27/2010 02:33 PM, bearophile wrote:

I have noticed a significant speed difference between foo1 and foo2 (D2 code):

import std.c.stdio: printf;

int foo1(int x, int y) {
 static int[int[2]] cache;
 int[2] args = [x, y];
 cache[args] = x;
 return x;
}

int foo2(int x, int y) {
 static struct Pair { int x, y; }
 static int[Pair] cache;
 Pair args = Pair(x, y);
 cache[args] = x;
 return x;
}

void main() {
 enum int N = 600;
 int tot;
 foreach (x; 1 .. N)
 foreach (y; 1 .. N)
 tot += foo2(x, y); // use foo1 or foo2 here
 printf(%d\n, tot);
}


Bye,
bearophile


On my machine, foo1 takes around 9 times longer.

Why is this?

Re: AAs of struct or array

[bearophile]

Ali Çehreli:
 Most of it comes from the use of that temporary. -O doesn't help either.

Right. I will probably put this in Bugzilla, even if it's a low priority thing.

Bye,
bearophile

Re: AAs of struct or array

[bearophile]

http://d.puremagic.com/issues/show_bug.cgi?id=4244