check for equality instead of counting > 0

might be faster on certain cpus

1 files changed, 6 insertions, 3 deletions

diff --git a/src/main.zig b/src/main.zig
index 0e8da4e..e6975be 100644
--- a/src/main.zig
+++ b/src/main.zig
@@ -1,5 +1,4 @@
 const SudokuSolver = struct {
-    const countEql = std.simd.countElementsWithValue;
     const join = std.simd.join;
     // Each cell exists in memory three times.
     // This makes it easy to compare a guess against all relevant cells simultaneously.
@@ -29,7 +28,9 @@ const SudokuSolver = struct {
         const constraints = join(self.rows[row], join(self.cols[col], self.boxes[boxOf(row, col)]));
         inline for (1..10) |n| {
             // A number is a possible move iff it does not already exist in the current row, col, or box.
-            if (countEql(constraints, @intCast(n)) == 0) {
+            const n_vec: @Vector(@typeInfo(@TypeOf(constraints)).vector.len, u8) = @splat(n);
+            const equals = constraints == n_vec;
+            if (!@reduce(.Or, equals)) {
                 cell_guesses.set(n - 1);
             }
         }
@@ -95,7 +96,9 @@ const SudokuSolver = struct {
 
     fn isSolved(self: SudokuSolver) bool {
         for (self.rows) |row| {
-            if (countEql(row, 0) > 0) return false;
+            const z_vec: @Vector(@typeInfo(@TypeOf(row)).vector.len, u8) = @splat(0);
+            const equals = row == z_vec;
+            if (@reduce(.Or, equals)) return false;
         }
         return true;
     }