andrey/munkres-rs
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Refactor control flow of algorithm

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* Get rid of enum Step
* Instead more explicity encode the control flow.
This commit is contained in:
Michael Neumann 2019-04-07 17:30:57 +02:00
parent bd8728ce2f
commit 44026fb680
1 changed files with 74 additions and 81 deletions
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155
src/lib.rs
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@ -48,32 +48,19 @@ pub enum Error {
MatrixNotSolvable,
}
#[derive(Debug, Eq, PartialEq)]
enum Step {
Step1,
Step2,
Step3,
Step4(Option<usize>),
Step5(Position),
Step6,
Failure(Error),
Done,
}
/// For each row of the matrix, find the smallest element and
/// subtract it from every element in its row. Go to Step 2.
fn step1<W>(c: &mut W) -> Step
fn step1<W>(c: &mut W)
where
W: Weights,
{
c.sub_min_of_each_row();
return Step::Step2;
}
/// Find a zero (Z) in the resulting matrix. If there is no starred
/// zero in its row or column, star Z. Repeat for each element in the
/// matrix. Go to Step 3.
fn step2<W>(c: &W, marks: &mut MarkMatrix, cov: &mut Coverage) -> Step
fn step2<W>(c: &W, marks: &mut MarkMatrix, cov: &mut Coverage)
where
W: Weights,
{
@ -94,14 +81,18 @@ where
// clear covers
cov.clear();
}
return Step::Step3;
#[derive(Debug, Eq, PartialEq)]
enum Step3 {
Done,
ContinueWithStep4 { star_count: usize },
}
/// Cover each column containing a starred zero. If K columns are
/// covered, the starred zeros describe a complete set of unique
/// assignments. In this case, Go to DONE, otherwise, Go to Step 4.
fn step3<W>(c: &W, marks: &MarkMatrix, cov: &mut Coverage) -> Step
fn step3<W>(c: &W, marks: &MarkMatrix, cov: &mut Coverage) -> Step3
where
W: Weights,
{
@ -110,27 +101,33 @@ where
assert!(marks.n() == n);
assert!(cov.n() == n);
let mut count: usize = 0;
let mut star_count: usize = 0;
marks.each_star(|Position { column, .. }| {
cov.cover_column(column);
count += 1;
star_count += 1;
});
if count >= n {
assert!(count == n);
Step::Done
if star_count >= n {
assert!(star_count == n);
Step3::Done
} else {
Step::Step4(Some(count))
Step3::ContinueWithStep4 { star_count }
}
}
#[derive(Debug, Eq, PartialEq)]
enum Step4 {
ContinueWithStep5 { z0_pos: Position },
ContinueWithStep6,
}
/// Find a noncovered zero and prime it. If there is no starred zero
/// in the row containing this primed zero, Go to Step 5. Otherwise,
/// cover this row and uncover the column containing the starred
/// zero. Continue in this manner until there are no uncovered zeros
/// left. Save the smallest uncovered value and Go to Step 6.
fn step4<W>(c: &W, marks: &mut MarkMatrix, cov: &mut Coverage) -> Step
fn step4<W>(c: &W, marks: &mut MarkMatrix, cov: &mut Coverage) -> Step4
where
W: Weights,
{
@ -142,9 +139,6 @@ where
loop {
// find uncovered zero element
match cov.find_uncovered_cell_column_row_order(|pos| c.is_element_zero(pos)) {
None => {
return Step::Step6;
}
Some(pos) => {
marks.prime(pos);
match marks.find_first_star_in_row(pos.row) {
@ -154,14 +148,22 @@ where
}
None => {
// in Python: self.Z0_r, self.Z0_c
return Step::Step5(pos);
return Step4::ContinueWithStep5 { z0_pos: pos };
}
}
}
None => {
return Step4::ContinueWithStep6;
}
}
}
}
#[derive(Debug, Eq, PartialEq)]
enum Step5 {
ContinueWithStep3,
}
/// Construct a series of alternating primed and starred zeros as
/// follows. Let Z0 represent the uncovered primed zero found in Step 4.
/// Let Z1 denote the starred zero in the column of Z0 (if any).
@ -175,7 +177,7 @@ fn step5(
cov: &mut Coverage,
z0_pos: Position,
path: &mut Vec<Position>,
) -> Step {
) -> Result<Step5, Error> {
let n = cov.n();
assert!(marks.n() == n);
@ -198,7 +200,7 @@ fn step5(
prev_col = column;
} else {
// XXX: Can this really happen?
return Step::Failure(Error::NoPrimeInRow);
return Err(Error::NoPrimeInRow);
}
}
None => {
@ -214,14 +216,19 @@ fn step5(
cov.clear();
marks.clear_primes();
return Step::Step3;
Ok(Step5::ContinueWithStep3)
}
#[derive(Debug, Eq, PartialEq)]
enum Step6 {
ContinueWithStep4,
}
/// Add the value found in Step 4 to every element of each covered
/// row, and subtract it from every element of each uncovered column.
/// Return to Step 4 without altering any stars, primes, or covered
/// lines.
fn step6<W>(c: &mut W, cov: &Coverage) -> Step
fn step6<W>(c: &mut W, cov: &Coverage) -> Result<Step6, Error>
where
W: Weights,
{
@ -252,9 +259,9 @@ where
}
}
Step::Step4(None)
Ok(Step6::ContinueWithStep4)
} else {
Step::Failure(Error::MatrixNotSolvable)
Err(Error::MatrixNotSolvable)
}
}
@ -272,46 +279,36 @@ where
let mut coverage = Coverage::new(n);
let mut path = Vec::with_capacity(n);
let mut step = Step::Step1;
loop {
match step {
Step::Step1 => step = step1(weights),
Step::Step2 => {
step = step2(weights, &mut marks, &mut coverage);
}
Step::Step3 => {
step = step3(weights, &marks, &mut coverage);
}
Step::Step4(_) => {
step = step4(weights, &mut marks, &mut coverage);
}
Step::Step5(z0_pos) => {
step = step5(&mut marks, &mut coverage, z0_pos, &mut path);
}
Step::Step6 => {
step = step6(weights, &coverage);
}
Step::Failure(err) => {
return Err(err);
}
Step::Done => {
break;
step1(weights);
step2(weights, &mut marks, &mut coverage);
'step3: loop {
match step3(weights, &marks, &mut coverage) {
Step3::ContinueWithStep4 { .. } => 'step4: loop {
match step4(weights, &mut marks, &mut coverage) {
Step4::ContinueWithStep5 { z0_pos } => {
match step5(&mut marks, &mut coverage, z0_pos, &mut path)? {
Step5::ContinueWithStep3 => {
continue 'step3;
}
}
}
Step4::ContinueWithStep6 => match step6(weights, &coverage)? {
Step6::ContinueWithStep4 => {
continue 'step4;
}
},
}
},
Step3::Done => {
break 'step3;
}
}
}
// now look for the starred elements
let mut matching = Vec::with_capacity(n);
for row in 0..n {
for column in 0..n {
let pos = Position { row, column };
if marks.is_star(pos) {
matching.push(pos);
}
}
}
marks.each_star(|pos| matching.push(pos));
assert!(matching.len() == n);
return Ok(matching);
}
@ -327,8 +324,7 @@ fn test_step1() {
let mut weights: WeightMatrix<i32> = WeightMatrix::from_row_vec(N, c);
let next_step = step1(&mut weights);
assert_eq!(Step::Step2, next_step);
step1(&mut weights);
let exp = &[0, 150, 100, 50, 250, 0, 0, 200, 50];
@ -344,8 +340,7 @@ fn test_step2() {
let mut marks = MarkMatrix::new(N);
let mut coverage = Coverage::new(N);
let next_step = step2(&weights, &mut marks, &mut coverage);
assert_eq!(Step::Step3, next_step);
step2(&weights, &mut marks, &mut coverage);
assert_eq!(true, marks.is_star(pos(0, 0)));
assert_eq!(false, marks.is_star(pos(0, 1)));
@ -381,7 +376,7 @@ fn test_step3() {
marks.star(pos(1, 2));
let next_step = step3(&weights, &marks, &mut coverage);
assert_eq!(Step::Step4(Some(2)), next_step);
assert_eq!(Step3::ContinueWithStep4 { star_count: 2 }, next_step);
assert_eq!(true, coverage.is_column_covered(0));
assert_eq!(false, coverage.is_column_covered(1));
@ -408,7 +403,7 @@ fn test_step4_case1() {
let next_step = step4(&weights, &mut marks, &mut coverage);
assert_eq!(Step::Step6, next_step);
assert_eq!(Step4::ContinueWithStep6, next_step);
// coverage did not change.
assert_eq!(true, coverage.is_column_covered(0));
@ -446,7 +441,7 @@ fn test_step6() {
let next_step = step6(&mut weights, &coverage);
assert_eq!(Step::Step4(None), next_step);
assert_eq!(Ok(Step6::ContinueWithStep4), next_step);
let exp = &[0, 0, 100, 50, 100, 0, 0, 50, 50];
@ -469,7 +464,7 @@ fn test_step4_case2() {
let next_step = step4(&weights, &mut marks, &mut coverage);
assert_eq!(Step::Step5(pos(2, 0)), next_step);
assert_eq!(Step4::ContinueWithStep5 { z0_pos: pos(2, 0) }, next_step);
// coverage DID CHANGE!
assert_eq!(false, coverage.is_column_covered(0));
@ -507,7 +502,7 @@ fn test_step5() {
let mut path = Vec::new();
let next_step = step5(&mut marks, &mut coverage, pos(2, 0), &mut path);
assert_eq!(Step::Step3, next_step);
assert_eq!(Ok(Step5::ContinueWithStep3), next_step);
// coverage DID CHANGE!
assert_eq!(false, coverage.is_column_covered(0));
@ -560,16 +555,14 @@ fn test_solve_equal_rows_stepwise() {
// step 1
let next_step = step1(&mut weights);
assert_eq!(Step::Step2, next_step);
step1(&mut weights);
assert_eq!(&[0, 0, 0, 0], weights.as_slice());
// step 2
let mut marks = MarkMatrix::new(N);
let mut coverage = Coverage::new(N);
let next_step = step2(&weights, &mut marks, &mut coverage);
assert_eq!(Step::Step3, next_step);
step2(&weights, &mut marks, &mut coverage);
assert!(coverage.all_uncovered());
assert!(marks.is_star(pos(0, 0)));
@ -579,7 +572,7 @@ fn test_solve_equal_rows_stepwise() {
// step 3
let next_step = step3(&weights, &mut marks, &mut coverage);
assert_eq!(Step::Done, next_step);
assert_eq!(Step3::Done, next_step);
}
#[cfg(test)]