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main.zig
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main.zig
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const std = @import("std");
var allocator = std.heap.c_allocator;
const Post = struct { _id: []const u8, title: []const u8, tags: [][]const u8 };
const Posts = []Post;
const TopPosts = struct { _id: *const []const u8, tags: *const [][]const u8, related: []*Post };
const stdout = std.io.getStdOut().writer();
const fxhash = @import("fxhash.zig");
inline fn top5(related: []*Post, score: []u8, ps: []Post) void {
var top_5 = [5]u8{ 0, 0, 0, 0, 0 };
var min_tags: u8 = 0;
for (score, 0..) |count, j| {
if (count > min_tags) {
// Find the position to insert
var pos: i8 = 3;
while (pos >= 0 and count > top_5[@intCast(pos)]) : (pos -= 1) {
top_5[@intCast(pos + 1)] = top_5[@intCast(pos)];
related[@intCast(pos + 1)] = related[@intCast(pos)];
}
top_5[@intCast(pos + 1)] = count;
related[@intCast(pos + 1)] = &ps[j];
min_tags = top_5[4];
}
}
}
pub fn main() !void {
const file = try std.fs.cwd().openFile("../posts.json", .{});
defer file.close();
var json_reader = std.json.reader(allocator, file.reader());
defer json_reader.deinit();
const parsed = try std.json.parseFromTokenSource(Posts, allocator, &json_reader, .{});
defer parsed.deinit();
const start = try std.time.Instant.now();
const ArrPosts = std.ArrayList(u32);
var map = fxhash.StringHashMap(ArrPosts).init(allocator);
defer map.deinit();
for (parsed.value, 0..) |post_ele, i| {
for (post_ele.tags) |tag| {
var get_or_put = try map.getOrPut(tag);
if (get_or_put.found_existing) {
try get_or_put.value_ptr.*.append(@intCast(i));
} else {
var temp = ArrPosts.init(allocator);
try temp.append(@intCast(i));
get_or_put.value_ptr.* = temp;
}
}
}
var op = try std.ArrayList(TopPosts).initCapacity(allocator, parsed.value.len);
op.expandToCapacity();
defer op.deinit();
var rl: []*Post = try allocator.alloc(*Post, parsed.value.len * 5);
defer allocator.free(rl);
var tagged_post_count: []u8 = try allocator.alloc(u8, parsed.value.len);
defer allocator.free(tagged_post_count);
for (0..parsed.value.len) |post_index| {
// reset tagged_post_count
@memset(tagged_post_count, 0);
for (parsed.value[post_index].tags) |tag| {
for (map.get(tag).?.items) |i_t| {
tagged_post_count[i_t] += 1;
}
}
tagged_post_count[post_index] = 0; // Don't count self
var related: []*Post = rl[post_index * 5 .. post_index * 5 + 5];
top5(related, tagged_post_count, parsed.value);
op.items[post_index] = .{ ._id = &parsed.value[post_index]._id, .tags = &parsed.value[post_index].tags, .related = related };
}
const end = try std.time.Instant.now();
try stdout.print("Processing time (w/o IO): {d}ms\n", .{@divFloor(end.since(start), std.time.ns_per_ms)});
const op_file = try std.fs.cwd().createFile("../related_posts_zig.json", .{});
defer op_file.close();
var buffered_writer = std.io.bufferedWriter(op_file.writer());
try std.json.stringify(try op.toOwnedSlice(), .{}, buffered_writer.writer());
try buffered_writer.flush();
}