In my machine the following D code compiled with release flag and
LDC performs over 230ms while the similar Go code performs under
120ms.
string smallestRepr(const string arg) {
import std.format : format;
const repeated = format!"%s%s"(arg, arg);
string result;
result.reserve(arg.length);
result = arg;
foreach (i; 1 .. arg.length) {
const slice = repeated[i .. i + arg.length];
if (slice < result)
result = slice;
}
return result;
}
unittest {
assert("cba".smallestRepr() == "acb");
}
void main(const string[] args) {
string[][const string] wordTable;
import std.stdio : writeln, lines, File;
foreach (string word; File(args[1]).lines()) {
word = word[0 .. $ - 1]; // strip the newline character
const string key = word.smallestRepr();
if (key in wordTable)
wordTable[key] ~= word;
else
wordTable[key] = [word];
}
foreach (key; wordTable.keys) {
if (wordTable[key].length == 4) {
writeln(wordTable[key]);
break;
}
}
}
---
package main
import (
"bufio"
"fmt"
"os"
)
func canonicalize(s string) string {
c := s + s[:len(s)-1]
best := s
for i := 1; i < len(s); i++ {
if c[i:i+len(s)] < best {
best = c[i : i+len(s)]
}
}
return best
}
func main() {
seen := make(map[string][]string)
inputFile, err := os.Open(os.Args[1])
defer inputFile.Close()
if err != nil {
os.Exit(1)
}
scanner := bufio.NewScanner(inputFile)
for scanner.Scan() {
word := scanner.Text()
n := canonicalize(word)
seen[n] = append(seen[n], word)
}
for _, words := range seen {
if len(words) == 4 {
fmt.Printf("%v\n", words)
break
}
}
}
The input file :
https://raw.githubusercontent.com/dolph/dictionary/master/enable1.txthttps://raw.githubusercontent.com/dolph/dictionary/master/enable1.txt
Problem description:
https://www.reddit.com/r/dailyprogrammer/comments/ffxabb/20200309_challenge_383_easy_necklace_matching
Where am I losing performance?
