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knucleotide: tune zig hash function and hash map load factor #472

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Mar 25, 2025
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knucleotide: tune zig hash function and hash map load factor #472

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24 changes: 14 additions & 10 deletions bench/algorithm/knucleotide/1.zig
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Original file line number Diff line number Diff line change
Expand Up @@ -85,7 +85,13 @@ pub fn readInput() ![]const u8 {
return buf;
}

const Map = std.AutoHashMapUnmanaged(Code, u32);
const CodeContext = struct {
pub fn eql(_: CodeContext, a: Code, b: Code) bool { return a.data == b.data; }
pub fn hash(_: CodeContext, c: Code) u64 { return c.data ^ (c.data >> 7); }
};

const Map = std.HashMapUnmanaged(Code, u32, CodeContext, 45);

const Iter = struct {
i: usize = 0,
input: []const u8,
Expand All @@ -102,6 +108,7 @@ const Iter = struct {
.mask = mask,
};
}

pub fn next(self: *Iter) ?Code {
if (self.i >= self.input.len) return null;
defer self.i += 1;
Expand All @@ -112,7 +119,7 @@ const Iter = struct {
};

fn genMap(seq: []const u8, n: usize, map: *Map) !void {
map.clearRetainingCapacity();
map.clearAndFree(global_allocator);
var iter = Iter.init(seq, n);
while (iter.next()) |code| {
const gop = try map.getOrPut(global_allocator, code);
Expand Down Expand Up @@ -161,11 +168,11 @@ fn printOcc(s: []const u8, map: *Map) !void {

pub fn main() !void {
const occs = [_][]const u8{
"GGTATTTTAATTTATAGT",
"GGTATTTTAATT",
"GGTATT",
"GGTA",
"GGT",
"GGTA",
"GGTATT",
"GGTATTTTAATT",
"GGTATTTTAATTTATAGT",
};
const input = try readInput();
var map: Map = .{};
Expand All @@ -174,11 +181,8 @@ pub fn main() !void {
try genMap(input, 2, &map);
try printMap(2, map);

var i = occs.len - 1;
while (true) : (i -= 1) {
const occ = occs[i];
for (occs) |occ| {
try genMap(input, occ.len, &map);
try printOcc(occ, &map);
if (i == 0) break;
}
}
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