Allow specifying multiple read directories

ext/src/chain_complex/chain_homotopy.rs

@@ -180,7 +180,7 @@ impl<
                 .add_generators_from_rows_ooo(source.t(), outputs);
         }
 
-        if let Some(dir) = self.save_dir.read() {
+        for dir in self.save_dir.read() {
             if let Some(mut f) = self
                 .left
                 .source

ext/src/nassau.rs

@@ -839,7 +839,7 @@ impl<M: ZeroModule<Algebra = MilnorAlgebra>> Resolution<M> {
             return Ok(());
         }
 
-        if let Some(dir) = self.save_dir.read() {
+        for dir in self.save_dir.read() {
             if let Some(mut f) = self
                 .save_file(SaveKind::NassauDifferential, b)
                 .open_file(dir.clone())
@@ -1009,12 +1009,13 @@ impl<M: ZeroModule<Algebra = MilnorAlgebra>> ChainComplex for Resolution<M> {
         for<'a> &'a mut T: Into<SliceMut<'a>>,
         for<'a> &'a S: Into<Slice<'a>>,
     {
-        let mut f = if let Some(dir) = self.save_dir.read() {
-            if let Some(f) = self.save_file(SaveKind::NassauQi, b).open_file(dir.clone()) {
-                f
-            } else {
-                return false;
-            }
+        let mut f = if let Some(f) = self
+            .save_dir
+            .read()
+            .flat_map(|dir| self.save_file(SaveKind::NassauQi, b).open_file(dir.clone()))
+            .next()
+        {
+            f
         } else {
             return false;
         };

ext/src/resolution.rs

@@ -199,7 +199,7 @@ where
 
         let p = self.prime();
 
-        if let Some(dir) = self.save_dir.read() {
+        for dir in self.save_dir.read() {
             if let Some(mut f) = self.save_file(SaveKind::Kernel, b).open_file(dir.clone()) {
                 return Subspace::from_bytes(p, &mut f)
                     .with_context(|| format!("Failed to read kernel at {b}"))
@@ -370,7 +370,7 @@ where
         target_res.compute_basis(b.t());
         let target_res_dimension = target_res.dimension(b.t());
 
-        if let Some(dir) = self.save_dir.read() {
+        for dir in self.save_dir.read() {
             if let Some(mut f) = self
                 .save_file(SaveKind::Differential, b)
                 .open_file(dir.clone())
@@ -814,12 +814,13 @@ where
                 } else if distance == 1 && b.s() < max.s() {
                     // We compute the kernel at the edge if necessary
                     let next_b = b + Bidegree::s_t(0, 1);
-                    if !self.has_computed_bidegree(b + Bidegree::s_t(1, 1))
-                        && (self.save_dir.is_none()
-                            || !self
-                                .save_file(SaveKind::Differential, b + Bidegree::s_t(1, 1))
-                                .exists(self.save_dir.read().cloned().unwrap()))
-                    {
+                    let kernel_bidegree_not_computed =
+                        !self.has_computed_bidegree(b + Bidegree::s_t(1, 1));
+                    let save_does_not_exist = !self.save_dir.read().any(|dir| {
+                        self.save_file(SaveKind::Differential, b + Bidegree::s_t(1, 1))
+                            .exists(dir.clone())
+                    });
+                    if kernel_bidegree_not_computed && save_does_not_exist {
                         scope.spawn(move |_| {
                             self.kernels.insert(next_b, self.get_kernel(next_b));
                             SenderData::send(next_b, false, sender);
@@ -888,17 +889,15 @@ where
             for (input, result) in inputs.iter().zip_eq(results) {
                 qi.apply(result.into(), 1, input.into());
             }
-            true
-        } else if let Some(dir) = self.save_dir.read() {
+            return true;
+        }
+        for dir in self.save_dir.read() {
             if let Some(mut f) = self.save_file(SaveKind::ResQi, b).open_file(dir.clone()) {
                 QuasiInverse::stream_quasi_inverse(self.prime(), &mut f, results, inputs).unwrap();
-                true
-            } else {
-                false
+                return true;
             }
-        } else {
-            false
         }
+        false
     }
 
     fn save_dir(&self) -> &SaveDirectory {

ext/src/resolution_homomorphism.rs

@@ -231,7 +231,7 @@ where
             );
         }
 
-        if let Some(dir) = self.save_dir.read() {
+        for dir in self.save_dir.read() {
             let mut outputs = Vec::with_capacity(num_gens);
 
             if let Some(mut f) = self

ext/src/save.rs

@@ -16,14 +16,16 @@ pub enum SaveDirectory {
     None,
     Combined(PathBuf),
     Split { read: PathBuf, write: PathBuf },
+    MultiRead { read: Vec<PathBuf>, write: PathBuf },
 }
 
 impl SaveDirectory {
-    pub fn read(&self) -> Option<&PathBuf> {
+    pub fn read(&self) -> Box<dyn Iterator<Item = &PathBuf> + '_> {
         match self {
-            Self::None => None,
-            Self::Combined(x) => Some(x),
-            Self::Split { read, .. } => Some(read),
+            Self::None => Box::new(std::iter::empty()),
+            Self::Combined(x) => Box::new(std::iter::once(x)),
+            Self::Split { read, .. } => Box::new(std::iter::once(read)),
+            Self::MultiRead { read, .. } => Box::new(read.iter()),
         }
     }
 
@@ -32,6 +34,7 @@ impl SaveDirectory {
             Self::None => None,
             Self::Combined(x) => Some(x),
             Self::Split { write, .. } => Some(write),
+            Self::MultiRead { write, .. } => Some(write),
         }
     }
 
@@ -45,6 +48,10 @@ impl SaveDirectory {
                 read.push(&p);
                 write.push(p);
             }
+            Self::MultiRead { read, write } => {
+                read.iter_mut().for_each(|r| r.push(&p));
+                write.push(p);
+            }
         }
     }
 

ext/src/secondary.rs

@@ -253,7 +253,7 @@ impl<A: PairAlgebra + Send + Sync> SecondaryHomotopy<A> {
                 b: gen.degree(),
                 idx: Some(gen.idx()),
             };
-            if let Some(dir) = dir.read() {
+            for dir in dir.read() {
                 if let Some(mut f) = save_file.open_file(dir.to_owned()) {
                     return SecondaryComposite::from_bytes(
                         Arc::clone(&self.target),
@@ -421,7 +421,7 @@ pub trait SecondaryLift: Sync + Sized {
             idx: Some(gen.idx()),
         };
 
-        if let Some(dir) = self.save_dir().read() {
+        for dir in self.save_dir().read() {
             if let Some(mut f) = save_file.open_file(dir.to_owned()) {
                 // The target dimension can depend on whether we resolved to stem
                 let dim = f.read_u64::<LittleEndian>().unwrap() as usize;
@@ -484,7 +484,7 @@ pub trait SecondaryLift: Sync + Sized {
                 return;
             }
             // Check if we have a saved homotopy
-            if let Some(dir) = self.save_dir().read() {
+            for dir in self.save_dir().read() {
                 let save_file = SaveFile {
                     algebra: self.algebra(),
                     kind: SaveKind::SecondaryHomotopy,
@@ -533,7 +533,7 @@ pub trait SecondaryLift: Sync + Sized {
         let num_gens = source.number_of_gens_in_degree(b.t());
         let target_dim = target.module(target_b.s()).dimension(target_b.t());
 
-        if let Some(dir) = self.save_dir().read() {
+        for dir in self.save_dir().read() {
             let save_file = SaveFile {
                 algebra: self.algebra(),
                 kind: SaveKind::SecondaryHomotopy,