Zig 0.17.0-dev (Split by item)

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interlace

Returns a vector whose elements alternates between those of each input vector. For example, interlace(.{[4]u32{11, 12, 13, 14}, [4]u32{21, 22, 23, 24}}) returns a vector containing .{11, 21, 12, 22, 13, 23, 14, 24}.

simd.interlace

pub fn interlace(vecs: anytype) @Vector(vectorLength(@TypeOf(vecs[0])) * vecs.len, std.meta.Child(@TypeOf(vecs[0])))

File

lib/std/simd.zig:159

Code

pub fn interlace(vecs: anytype) @Vector(vectorLength(@TypeOf(vecs[0])) * vecs.len, std.meta.Child(@TypeOf(vecs[0]))) {
    const VecType = @TypeOf(vecs[0]);
    const vecs_arr = @as([vecs.len]VecType, vecs);
    const Child = std.meta.Child(@TypeOf(vecs_arr[0]));

    if (vecs_arr.len == 1) return vecs_arr[0];

    const a_vec_count = (1 + vecs_arr.len) >> 1;
    const b_vec_count = vecs_arr.len >> 1;

    const a = interlace(@as(*const [a_vec_count]VecType, @ptrCast(vecs_arr[0..a_vec_count])).*);
    const b = interlace(@as(*const [b_vec_count]VecType, @ptrCast(vecs_arr[a_vec_count..])).*);

    const a_len = vectorLength(@TypeOf(a));
    const b_len = vectorLength(@TypeOf(b));
    const len = a_len + b_len;

    const indices = comptime blk: {
        const Vi32 = @Vector(len, i32);
        const count_up = iota(i32, len);
        const cycle = @divFloor(count_up, @as(Vi32, @splat(@intCast(vecs_arr.len))));
        const select_mask = repeat(len, join(@as(@Vector(a_vec_count, bool), @splat(true)), @as(@Vector(b_vec_count, bool), @splat(false))));
        const a_indices = count_up - cycle * @as(Vi32, @splat(@intCast(b_vec_count)));
        const b_indices = shiftElementsRight(count_up - cycle * @as(Vi32, @splat(@intCast(a_vec_count))), a_vec_count, 0);
        break :blk @select(i32, select_mask, a_indices, ~b_indices);
    };

    return @shuffle(Child, a, b, indices);
}