Re: my first D program (and benchmark against perl)

[Daniel Kozak via Digitalmars-d-learn]

On Thursday, 12 November 2015 at 12:25:08 UTC, Daniel Kozak wrote:
V Thu, 12 Nov 2015 12:13:10 +0000
perlancar via Digitalmars-d-learn 
<digitalmars-d-learn@puremagic.com>
napsáno:
On Wednesday, 11 November 2015 at 14:20:51 UTC, Rikki 
Cattermole wrote:
> I turned it into mostly using large allocations, instead of
> small ones.
> Although I'd recommend using Appender instead of my custom
> functions for this.
>
> Oh and for me, I got it at 2 secs, 513 ms, 397 μs, and 5
> hnsecs. Unoptimized, using dmd.
> When release mode is enabled on dmd: 1 sec, 550 ms, 838 μs, 
> and
> 9 hnsecs. So significant improvement even with dmds awful
> optimizer.

Hi Rikki,

Thanks. With your version, I've managed to be ~4x faster:

dmd          : 0m1.588s
dmd (release): 0m1.010s
gdc          : 0m2.093s
ldc          : 0m1.594s

Perl version : 0m11.391s

So, I'm satisfied enough with the speed for now. Turns out dmd 
is not always slower.

It depends which flags do you use on ldc and gdc


ldc (-singleobj -release -O3 -boundscheck=off)
gdc (-O3 -finline -frelease -fno-bounds-check)

import std.stdio;

auto fmttable(string[][] table) {

    import std.array : appender, uninitializedArray;
    import std.range : take, repeat;
    import std.exception : assumeUnique;


    if (table.length == 0) return "";
    // column widths
    auto widths = new int[](table[0].length);
	size_t total = (table[0].length + 1) * table.length + 
table.length;	
        
    foreach (rownum, row; table) {
        foreach (colnum, cell; row) {
            if (cell.length > widths[colnum])
                widths[colnum] = cast(int)cell.length;
        }
    }

    foreach (colWidth; widths)
    {
                total += colWidth * table.length;
        }       
        
    auto res = appender(uninitializedArray!(char[])(total));
    res.clear();

    foreach (row; table) {
        res ~= "|";
        foreach (colnum, cell; row) {
            int l = widths[colnum] - cast(int)cell.length;
            res ~= cell;
            if (l)
                res ~= ' '.repeat().take(l);
            res ~= "|";
        }
        res.put("\n");
    }

     return res.data.assumeUnique();
}

void main() {

    auto table = [
        ["row1.1", "row1.2  ", "row1.3"],
        ["row2.1", "row2.2", "row2.3"],
        ["row3.1", "row3.2", "row3.3  "],
        ["row4.1", "row4.2", "row4.3"],
        ["row5.1", "row5.2", "row5.3"],
    ];

    writeln(fmttable(table));
    for (int i=0; i < 1000000; ++i) {
        fmttable(table);
    }
}

dmd -O -release -inline -boundscheck=off  asciitable.d

real    0m1.463s
user    0m1.453s
sys     0m0.003s


ldc2 -singleobj -release -O3 -boundscheck=off asciitable.d

real    0m0.945s
user    0m0.940s
sys     0m0.000s

gdc -O3 -finline -frelease -fno-bounds-check -o asciitable 
asciitable.d

real    0m0.618s
user    0m0.613s
sys     0m0.000s


perl:

real    0m14.198s
user    0m14.170s
sys     0m0.000s