At the bottom of this post there are two little test programs that may show a
problem with static arrays.
D code compiled with DMD 1.038:
dmd test_d.d
Compile time: 8.29 s
Resulting exe and obj:
17.756.188 test_d.exe
2.390 test_d.map
17.734.261 test_d.obj
C code compiled with DMC 8.42n:
dmc test_c.c
Compile time: 0.04 s
Resulting exe:
51.740 test_c.exe
C code compiled with GCC (4.2.1):
gcc test_c.c -o test_c
Compile time: 0.16 s
Resulting exe:
16.781 test_c.exe
C code compiled with LLVM-GCC (2.5):
llvm-gcc test_c.c -o test_c
Compile time: 0.11 s
Resulting exe:
13.462 test_c.exe
(The following code is just reduced toy, but the full program runs up to about
13 times faster with static arrays, so I'd like to use them instead of the
dynamic ones.)
Using obj2asm on the test_d.obj it's made mostly of:
_D6test_d1aG3G65G65G130f:
db 000h,000h,0c0h,07fh,000h,000h,0c0h,07fh
db 000h,000h,0c0h,07fh,000h,000h,0c0h,07fh
db 000h,000h,0c0h,07fh,000h,000h,0c0h,07fh
db 000h,000h,0c0h,07fh,000h,000h,0c0h,07fh
...
-------------------------
// C code:
#include "stdio.h"
#define N 65
#define M (N+N)
float a[3][N][N][M];
float b[4][N][N][M];
float c[N][N][M];
int main() {
int i, j, k;
for (i = 0; i < N; i++)
for (j = 0; j < N; j++)
for (k = 0; k < M; k++) {
a[0][i][j][k] = 0.0;
a[1][i][j][k] = 0.0;
a[2][i][j][k] = 0.0;
b[0][i][j][k] = 0.0;
b[1][i][j][k] = 0.0;
b[2][i][j][k] = 0.0;
b[3][i][j][k] = 0.0;
c[i][j][k] = 0.0;
}
printf("%f %f %f\n", a[2][10][10][10], a[2][10][10][10], c[10][10][10]);
return 0;
}
-------------------------
// D code, it's the same,
// I have just changed the first 3 lines.
import std.c.stdio: printf;
const int N = 65;
const int M = (N+N);
float a[3][N][N][M];
float b[4][N][N][M];
float c[N][N][M];
int main() {
int i, j, k;
for (i = 0; i < N; i++)
for (j = 0; j < N; j++)
for (k = 0; k < M; k++) {
a[0][i][j][k] = 0.0;
a[1][i][j][k] = 0.0;
a[2][i][j][k] = 0.0;
b[0][i][j][k] = 0.0;
b[1][i][j][k] = 0.0;
b[2][i][j][k] = 0.0;
b[3][i][j][k] = 0.0;
c[i][j][k] = 0.0;
}
printf("%f %f %f\n", a[2][10][10][10], a[2][10][10][10], c[10][10][10]);
return 0;
}
Bye,
bearophile
