rust version: old method comparable to method in main

.cargo/config.toml

@@ -0,0 +1,2 @@
+[build]
+rustflags = ["-C", "target-cpu=native", "-C", "target-feature=+crt-static"]

Cargo.lock

@@ -4,4 +4,4 @@ version = 3
 
 [[package]]
 name = "sudk"
-version = "0.1.1"
+version = "0.1.0"

Cargo.toml

@@ -1,14 +1,9 @@
 [package]
 name = "sudk"
-version = "0.1.1"
+version = "0.1.0"
 authors = ["ddidderr <ddidderr@paul.network>"]
 edition = "2021"
 
-[lints.clippy]
-pedantic = { level = "warn", priority = -1 }
-todo = "warn"
-unwrap_used = "warn"
-
 [dependencies]
 
 [profile.release]

c_version/clangtest

@@ -1,6 +1,6 @@
 #!/bin/bash
 set -e
 
-clang -Weverything -Wno-unsafe-buffer-usage -Werror -O3 -march=native -flto -std=c17 -fstack-protector-all -s -o sudk_c "$1"
+clang -Wall -Wextra -Weverything -Werror -O3 -march=native -flto -std=c17 -fstack-protector-all -s -o sudk_c "$1"
 
 time ./sudk_c

c_version/sudk_stack.c

@@ -5,7 +5,7 @@
 #include <stdlib.h>
 #include <sys/types.h>
 
-static inline void Print_Clear(void) { printf("\x1b\x5b\x48\x1b\x5b\x32\x4a"); }
+static inline void Print_Clear() { printf("\x1b\x5b\x48\x1b\x5b\x32\x4a"); }
 
 typedef struct Sudoku {
   uint8_t *field;
@@ -258,7 +258,7 @@ static void Sudoku_Free(Sudoku *s) {
   s = NULL;
 }
 
-int main(void) {
+int main() {
   Sudoku *s = Sudoku_New(3);
   Sudoku_Print(s);
   Sudoku_SolveBacktracking(s);

rustfmt.toml

@@ -1,3 +0,0 @@
-group_imports = "StdExternalCrate"
-imports_granularity = "Crate"
-imports_layout = "HorizontalVertical"

src/main.rs

@@ -4,26 +4,9 @@ const BLOCK_SIZE: usize = 3;
 const SIZE: usize = BLOCK_SIZE * BLOCK_SIZE;
 const NUM_FIELDS: usize = SIZE * SIZE;
 
-fn print_gray() {
-    print!("\x1b\x5b\x31\x3b\x33\x30\x6d");
-}
-
-fn print_green() {
-    print!("\x1b\x5b\x31\x3b\x33\x32\x6d");
-}
-
-fn print_neutral() {
-    print!("\x1b\x5b\x31\x3b\x30\x6d");
-}
-
-fn print_clear() {
-    print!("\x1b\x5b\x48\x1b\x5b\x32\x4a");
-}
-
 struct SField {
     field: Vec<u8>,
-    skip_forward: Vec<u8>,
+    fixed: Vec<bool>,
-    skip_backward: Vec<u8>,
     pos: usize,
     possible_values: Vec<Vec<u8>>,
 }
@@ -43,72 +26,32 @@ impl SField {
             0,0,8,2,0,0,0,6,0,
         ];
 
-        let mut sudoku = SField {
+        let mut fixed = Vec::with_capacity(SIZE * SIZE);
+        field.iter().for_each(|e| {
+            if *e == 0 {
+                fixed.push(false);
+            } else {
+                fixed.push(true);
+            }
+        });
+
+        SField {
             field,
-            skip_forward: vec![0; NUM_FIELDS + 1],
+            fixed,
-            skip_backward: vec![0; NUM_FIELDS + 1],
             pos: 0,
-            possible_values: vec![vec![]; NUM_FIELDS],
+            possible_values: vec![vec![]; SIZE * SIZE],
-        };
-
-        sudoku.build_possible_values_db();
-
-        sudoku.build_skip_dbs();
-
-        sudoku
-    }
-
-    fn build_skip_dbs(&mut self) {
-        fn find_fixed_streak_forward(mut idx: usize, field: &[u8]) -> u8 {
-            let mut fixed_count = 1;
-            idx += 1;
-
-            while idx < NUM_FIELDS && field[idx] > 0 {
-                fixed_count += 1;
-                idx += 1;
-            }
-
-            fixed_count
-        }
-
-        fn find_fixed_streak_backward(mut idx: usize, field: &[u8]) -> u8 {
-            let mut fixed_count = 1;
-            idx -= 1;
-
-            while idx < NUM_FIELDS && field[idx] > 0 {
-                fixed_count += 1;
-                idx -= 1;
-            }
-
-            fixed_count
-        }
-
-        let fwd = &mut self.skip_forward;
-        for (idx, nr) in self.field.iter().enumerate() {
-            match nr {
-                0 => fwd[idx] = *nr,
-                _ => fwd[idx] = find_fixed_streak_forward(idx, &self.field),
-            }
-        }
-
-        let bwd = &mut self.skip_backward;
-        for (idx, nr) in self.field.iter().enumerate().rev() {
-            match nr {
-                0 => bwd[idx + 1] = *nr,
-                _ => bwd[idx + 1] = find_fixed_streak_backward(idx, &self.field),
-            }
         }
     }
 
     fn build_possible_values_db(&mut self) {
         for idx in 0..NUM_FIELDS {
-            if self.field[idx] != 0 {
+            if self.fixed[idx] {
                 continue;
             }
             self.pos = idx;
             // try all values between 1 and =self.size and remember the good ones
             let mut good_ones = Vec::with_capacity(SIZE);
-            for nr in 1..=(u8::try_from(SIZE).expect("SIZE is too big")) {
+            for nr in 1..=(SIZE as u8) {
                 if self.ok(nr) {
                     good_ones.push(nr);
                 }
@@ -120,35 +63,71 @@ impl SField {
 
     pub fn solve_backtracking(&mut self) -> bool {
         let mut num_solutions = 0;
-
         loop {
-            if !self.put_valid_nr() {
+            if self.is_end() {
-                self.clear_current_field();
+                num_solutions += 1;
-                if !self.prev() {
+
-                    print_clear();
+                if num_solutions % 10_000 == 0 {
+                    self.print_clear();
                     self.print();
-                    println!("Number of solutions: {num_solutions}");
+                    println!("Number of solutions: {}", num_solutions);
-                    break;
                 }
+
+                if self.is_fixed() {
+                    continue;
+                }
+                self.clear_current_field();
+                self.prev();
+                self.goto_prev_free_field();
+            }
+
+            if self.is_fixed() {
+                self.next();
                 continue;
             }
 
-            if !self.next() {
+            if self.goto_next_free_field() {
-                num_solutions += 1;
+                if self.put_valid_nr() {
-                if num_solutions % 10_000 == 0 {
+                    self.next();
-                    print_clear();
+                    continue;
-                    self.print();
+                } else {
-                    println!("Number of solutions: {num_solutions}");
+                    self.clear_current_field();
+                    if !self.prev() {
+                        println!("Number of solutions: {}", num_solutions);
+                        break;
+                    }
+                    if !self.goto_prev_free_field() {
+                        println!("Number of solutions: {}", num_solutions);
+                        break;
+                    }
                 }
-
-                self.clear_current_field();
-                self.prev();
             }
         }
 
         num_solutions > 0
     }
 
+    #[inline(always)]
+    fn print_gray(&self) {
+        print!("\x1b\x5b\x31\x3b\x33\x30\x6d");
+    }
+
+    #[inline(always)]
+    fn print_green(&self) {
+        print!("\x1b\x5b\x31\x3b\x33\x32\x6d");
+    }
+
+    #[inline(always)]
+    fn print_neutral(&self) {
+        print!("\x1b\x5b\x31\x3b\x30\x6d");
+    }
+
+    #[inline(always)]
+    fn print_clear(&self) {
+        print!("\x1b\x5b\x48\x1b\x5b\x32\x4a");
+    }
+
+    #[inline(always)]
     fn print(&self) {
         for i in 0..NUM_FIELDS {
             if i != 0 && i % SIZE == 0 {
@@ -156,33 +135,73 @@ impl SField {
             }
 
             if i == self.pos {
-                print_green();
+                self.print_green();
             } else if self.get_field_at_pos(i) == 0 {
-                print_gray();
+                self.print_gray();
             }
 
             print!("{:2} ", self.get_field_at_pos(i));
 
             if i == self.pos || self.get_field_at_pos(i) == 0 {
-                print_neutral();
+                self.print_neutral();
             }
         }
         println!();
     }
 
+    #[inline(always)]
     fn clear_current_field(&mut self) {
         self.set(0);
     }
 
+    #[inline(always)]
+    fn goto_prev_free_field(&mut self) -> bool {
+        while {
+            if !self.is_fixed() {
+                return true;
+            }
+            self.prev()
+        } {}
+
+        false
+    }
+
+    #[inline(always)]
+    fn goto_next_free_field(&mut self) -> bool {
+        while {
+            if !self.is_fixed() {
+                return true;
+            }
+            self.next()
+        } {}
+
+        false
+    }
+
+    #[inline(always)]
+    fn _put_valid_nr(&mut self) -> bool {
+        let current_nr = self.get_field_at_pos(self.pos);
+
+        for nr in current_nr..(SIZE + 1) as u8 {
+            if self.ok(nr) {
+                self.set(nr);
+                return true;
+            }
+        }
+
+        false
+    }
+
+    #[inline(always)]
     fn put_valid_nr(&mut self) -> bool {
         let current_nr = self.get_field_at_pos(self.pos);
 
         // safety:
         //     self.possible_vals is initialized with self.size * self.size
         //     so self.pos can safely be used to index here
-        let possible_vals = &self.possible_values[self.pos];
+        let possible_vals = unsafe { self.possible_values.get_unchecked(self.pos) };
 
-        for nr in possible_vals {
+        for nr in possible_vals.iter() {
             if *nr <= current_nr {
                 continue;
             }
@@ -195,10 +214,32 @@ impl SField {
         false
     }
 
+    #[inline(always)]
+    fn is_end(&self) -> bool {
+        !self.field.contains(&0)
+    }
+
+    #[inline(always)]
     fn ok(&self, nr: u8) -> bool {
         self.block_ok(nr) && self.row_ok(nr) && self.col_ok(nr)
     }
 
+    #[inline(always)]
+    fn _pos_to_xy(&self) -> (usize, usize) {
+        let y = self.pos / SIZE;
+        let x = self.pos % SIZE;
+        (x + 1, y + 1)
+    }
+
+    #[inline(always)]
+    fn is_fixed(&self) -> bool {
+        // safety: self.pos can be used to index the field unchecked
+        //         since the only methods modifying self.pos are
+        //         `next()` and `prev()` and they do bounds checking
+        unsafe { *self.fixed.get_unchecked(self.pos) }
+    }
+
+    #[inline(always)]
     fn get_field_at_pos(&self, pos: usize) -> u8 {
         // safety:
         //     TODO
@@ -207,22 +248,26 @@ impl SField {
         unsafe { *self.field.get_unchecked(pos) }
     }
 
+    #[inline(always)]
     fn set(&mut self, nr: u8) {
         self.field[self.pos] = nr;
     }
 
+    #[inline(always)]
     fn get_row(&self, row: &mut [u8; SIZE]) {
         for (idx, row_elem) in row.iter_mut().enumerate() {
             *row_elem = self.get_field_at_pos((self.pos / SIZE) * SIZE + idx);
         }
     }
 
+    #[inline(always)]
     fn get_col(&self, col: &mut [u8; SIZE]) {
         for (idx, col_elem) in col.iter_mut().enumerate() {
             *col_elem = self.get_field_at_pos(idx * SIZE + self.pos % SIZE);
         }
     }
 
+    #[inline(always)]
     fn get_block(&self, block: &mut [u8; SIZE]) {
         let block_start_row = self.pos / SIZE / BLOCK_SIZE * BLOCK_SIZE;
         let block_start_col = self.pos % SIZE / BLOCK_SIZE * BLOCK_SIZE;
@@ -235,46 +280,48 @@ impl SField {
         }
     }
 
+    #[inline(always)]
     fn block_ok(&self, nr: u8) -> bool {
         let mut block = [0; SIZE];
         self.get_block(&mut block);
         !block.contains(&nr)
     }
 
+    #[inline(always)]
     fn row_ok(&self, nr: u8) -> bool {
         let mut row = [0; SIZE];
         self.get_row(&mut row);
         !row.contains(&nr)
     }
 
+    #[inline(always)]
     fn col_ok(&self, nr: u8) -> bool {
         let mut col = [0; SIZE];
         self.get_col(&mut col);
         !col.contains(&nr)
     }
 
+    #[inline(always)]
     fn next(&mut self) -> bool {
-        let new_pos = self.pos + 1 + self.skip_forward[self.pos + 1] as usize;
+        if self.pos == NUM_FIELDS - 1 {
-
-        if new_pos >= NUM_FIELDS {
             return false;
         }
 
-        self.pos = new_pos;
+        self.pos += 1;
         true
     }
 
+    #[inline(always)]
     fn prev(&mut self) -> bool {
-        let new_pos = self.pos - 1 - self.skip_backward[self.pos] as usize;
+        if self.pos == 0 {
-
-        if new_pos >= NUM_FIELDS {
             return false;
         }
 
-        self.pos = new_pos;
+        self.pos -= 1;
         true
     }
 
+    #[inline(always)]
     fn solve(&mut self) {
         let now = Instant::now();
         if !self.solve_backtracking() {
@@ -284,7 +331,17 @@ impl SField {
     }
 }
 
-fn main() {
+fn run() -> Result<(), String> {
     let mut field = SField::new();
+
+    field.build_possible_values_db();
+
     field.solve();
+    Ok(())
+}
+
+fn main() {
+    if let Err(e) = run() {
+        println!("{}", e)
+    }
 }