On Monday, 21 April 2014 at 00:11:14 UTC, Jay Norwood wrote:
So this printDiamonde2b example had the fastest time of the
solutions, and had similar times on all three builds. The ldc2
compiler build is performing best in most examples on ubuntu.
void printDiamonde2b(in uint N)
{
uint N2 = N/2;
char pSpace[] = uninitializedArray!(char[])(N2);
pSpace[] = ' ';
char pStars[] = uninitializedArray!(char[])(N+1);
pStars[] = '*';
pStars[$-1] = '\n';
auto w = appender!(char[])();
w.reserve(N*3);
foreach (n ; 0 .. N2 + 1){
w.put(pSpace[0 .. N2 - n]);
w.put(pStars[$-2*n-2 .. $]);
}
foreach_reverse (n ; 0 .. N2){
w.put(pSpace[0 .. N2 - n]);
w.put(pStars[$-2*n-2 .. $]);
}
write(w.data);
}
With this slightly tweaked solution, I can get times of roughly
50% to 100% faster, on my dmd-linux box:
//----
void printDiamonde2monarch(in uint N)
{
uint N2 = N/2;
char[] pBuf = uninitializedArray!(char[])(N + N2);
pBuf[ 0 .. N2] = ' ';
pBuf[N2 .. $] = '*';
auto slice = uninitializedArray!(char[])(3*N2*N2 + 4*N);
size_t i;
foreach (n ; 0 .. N2 + 1){
auto w = 1 + N2 + n;
slice[i .. i + w] = pBuf[n .. w + n];
slice[(i+=w)++]='\n';
}
foreach_reverse (n ; 0 .. N2){
auto w = 1 + N2 + n;
slice[i .. i + w] = pBuf[n .. w + n];
slice[(i+=w)++]='\n';
}
write(slice[0 .. i]);
}
//----
The two "key" points here, first, is to avoid using appender.
Second, instead of having two buffer: " " and "******\n", and
two do two "slice copies", to only have 1 buffer " *****", and
to do 1 slice copy, and a single '\n' write. At this point, I'm
not sure how we could be going any faster, short of using
alloca...
How does this hold up on your environment?
