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perf: reduce string comparisons in Levenshtein distance calculation #266

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perf: reduce string comparisons in Levenshtein distance calculation #266

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a6ee1f7
Update code.zig
ramsyana Dec 19, 2024
b6c502f
Update code.zig
ramsyana Dec 20, 2024
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27 changes: 10 additions & 17 deletions levenshtein/zig/code.zig
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Original file line number Diff line number Diff line change
Expand Up @@ -12,39 +12,34 @@ fn levenshteinDistance(s1: []const u8, s2: []const u8) usize {
// Make s1 the shorter string for space optimization
const str1 = if (s1.len > s2.len) s2 else s1;
const str2 = if (s1.len > s2.len) s1 else s2;

const m = str1.len;
const n = str2.len;

// Use two arrays instead of full matrix for space optimization
var prev_row: [256]usize = undefined;
var curr_row: [256]usize = undefined;
var prev_row: [1024]usize = undefined;
var curr_row: [1024]usize = undefined;

// Initialize first row
for (0..m + 1) |i| {
prev_row[i] = i;
}

// Main computation loop
var j: usize = 1;
while (j <= n) : (j += 1) {
curr_row[0] = j;

var i: usize = 1;
while (i <= m) : (i += 1) {

const cost: usize = if (str1[i - 1] == str2[j - 1]) 0 else 1;

// Calculate minimum of three operations
curr_row[i] = @min(
@min(
prev_row[i] + 1, // deletion
curr_row[i - 1] + 1, // insertion
curr_row[i - 1] + 1 // insertion
),
prev_row[i - 1] + cost // substitution
);
}

// Swap rows
// Swap rows
@memcpy(prev_row[0..m + 1], curr_row[0..m + 1]);
}

Expand All @@ -71,15 +66,13 @@ pub fn main() !void {
// Compare all pairs of strings
var i: usize = 1;
while (i < args.len) : (i += 1) {
var j: usize = 1;
var j: usize = i + 1; // Start from i+1 to avoid redundant comparisons
while (j < args.len) : (j += 1) {
if (i != j) {
const distance = levenshteinDistance(args[i], args[j]);
if (min_distance == -1 or distance < @as(usize, @intCast(min_distance))) {
min_distance = @as(isize, @intCast(distance));
}
times += 1;
const distance = levenshteinDistance(args[i], args[j]);
if (min_distance == -1 or distance < @as(usize, @intCast(min_distance))) {
min_distance = @as(isize, @intCast(distance));
}
times += 1;
}
}

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