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add tail merge

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Brendan Hansknecht 2024-07-23 22:43:14 -07:00
parent eb8c91775f
commit 5bc97b58c8
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1 changed files with 54 additions and 2 deletions
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56
crates/compiler/builtins/bitcode/src/sort.zig
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@ -75,6 +75,35 @@ fn quadsort_direct(
// ================ Unbalanced Merges =========================================
/// Merges the remaining blocks at the tail of the array.
fn tail_merge(
array: [*]u8,
len: usize,
swap: [*]u8,
swap_len: usize,
block_len: usize,
cmp_data: Opaque,
cmp: CompareFn,
element_width: usize,
copy: CopyFn,
) void {
const end_ptr = array + len * element_width;
var current_block_len = block_len;
while (current_block_len < len and current_block_len <= swap_len) {
var arr_ptr = array;
while (@intFromPtr(arr_ptr) + current_block_len * element_width < @intFromPtr(end_ptr)) : (arr_ptr += 2 * current_block_len * element_width) {
if (@intFromPtr(arr_ptr) + 2 * current_block_len * element_width < @intFromPtr(end_ptr)) {
partial_backwards_merge(arr_ptr, 2 * current_block_len, swap, swap_len, current_block_len, cmp_data, cmp, element_width, copy);
continue;
}
const rem_len = (@intFromPtr(end_ptr) - @intFromPtr(arr_ptr)) / element_width;
partial_backwards_merge(arr_ptr, rem_len, swap, swap_len, current_block_len, cmp_data, cmp, element_width, copy);
break;
}
current_block_len *= 2;
}
}
/// Merges a full left block with a smaller than block size right chunk.
/// The merge goes from tail to head.
fn partial_backwards_merge(
@ -425,6 +454,29 @@ fn partial_forward_merge_left_head_2(
return false;
}
test "tail_merge" {
{
const expected = [10]i64{ 1, 2, 3, 4, 5, 6, 7, 8, 9, 10 };
var arr: [10]i64 = undefined;
var arr_ptr = @as([*]u8, @ptrCast(&arr[0]));
var swap: [10]i64 = undefined;
var swap_ptr = @as([*]u8, @ptrCast(&swap[0]));
arr = [10]i64{ 7, 8, 5, 6, 3, 4, 1, 2, 9, 10 };
tail_merge(arr_ptr, 10, swap_ptr, 10, 2, null, &test_i64_compare, @sizeOf(i64), &test_i64_copy);
try testing.expectEqual(arr, expected);
arr = [10]i64{ 7, 8, 5, 6, 3, 4, 1, 2, 9, 10 };
tail_merge(arr_ptr, 9, swap_ptr, 9, 2, null, &test_i64_compare, @sizeOf(i64), &test_i64_copy);
try testing.expectEqual(arr, expected);
arr = [10]i64{ 3, 4, 6, 9, 1, 2, 5, 10, 7, 8 };
tail_merge(arr_ptr, 10, swap_ptr, 10, 4, null, &test_i64_compare, @sizeOf(i64), &test_i64_copy);
try testing.expectEqual(arr, expected);
}
}
test "partial_backwards_merge" {
{
const expected = [10]i64{ 1, 2, 3, 4, 5, 6, 7, 8, 9, 10 };
@ -1544,7 +1596,7 @@ test "parity_merge_two" {
try testing.expectEqual(dest, [4]i64{ 1, 2, 3, 4 });
}
test "head_merge" {
test "head_branchless_merge" {
var dest = [6]i64{ 0, 0, 0, 0, 0, 0 };
var left = [4]i64{ 1, 7, 10, 22 };
var right = [4]i64{ 2, 2, 8, 22 };
@ -1562,7 +1614,7 @@ test "head_merge" {
try testing.expectEqual(dest, [6]i64{ 1, 2, 2, 7, 8, 10 });
}
test "tail_merge" {
test "tail_branchless_merge" {
var dest = [6]i64{ 0, 0, 0, 0, 0, 0 };
var left = [4]i64{ -22, 1, 7, 10 };
var right = [4]i64{ -22, 2, 2, 8 };