From ddd6e61f530eebf5f1d3ceec2c4cbdb9ea0708d2 Mon Sep 17 00:00:00 2001
From: Christoph Jabs <christoph.jabs@helsinki.fi>
Date: Tue, 2 Apr 2024 14:07:44 +0300
Subject: [PATCH] perf: add `BufWriter` when writing to file

resolves #76
---
 rustsat/src/bench.rs              | 19 +++++++++++++++++++
 rustsat/src/instances/fio.rs      | 20 +++++++++++---------
 rustsat/src/instances/multiopt.rs |  8 ++++++++
 rustsat/src/instances/opt.rs      |  8 ++++++++
 rustsat/src/instances/sat.rs      |  8 ++++++++
 5 files changed, 54 insertions(+), 9 deletions(-)

diff --git a/rustsat/src/bench.rs b/rustsat/src/bench.rs
index 478d5297..7bb79c5a 100644
--- a/rustsat/src/bench.rs
+++ b/rustsat/src/bench.rs
@@ -154,3 +154,22 @@ mod pb_enc {
         b.iter(|| build_full_ub::<DynamicPolyWatchdog>(&lits!()));
     }
 }
+
+mod fio {
+    extern crate test;
+
+    use test::Bencher;
+
+    use crate::instances::SatInstance;
+
+    fn read_write_dimacs() {
+        let inst: SatInstance =
+            SatInstance::from_dimacs_path("./data/minisat-segfault.cnf").unwrap();
+        inst.to_dimacs_path("/tmp/rustsat-test.cnf").unwrap();
+    }
+
+    #[bench]
+    fn read_write(b: &mut Bencher) {
+        b.iter(|| read_write_dimacs());
+    }
+}
diff --git a/rustsat/src/instances/fio.rs b/rustsat/src/instances/fio.rs
index 1fa11360..3ee2cc9f 100644
--- a/rustsat/src/instances/fio.rs
+++ b/rustsat/src/instances/fio.rs
@@ -43,24 +43,26 @@ pub(crate) fn open_compressed_uncompressed_write<P: AsRef<Path>>(
     path: P,
 ) -> Result<Box<dyn io::Write>, io::Error> {
     let path = path.as_ref();
-    let raw_reader = File::create(path)?;
+    let raw_writer = File::create(path)?;
     #[cfg(feature = "compression")]
     if let Some(ext) = path.extension() {
         if ext.eq_ignore_ascii_case(std::ffi::OsStr::new("bz2")) {
-            return Ok(Box::new(bzip2::write::BzEncoder::new(
-                raw_reader,
+            return Ok(Box::new(io::BufWriter::new(bzip2::write::BzEncoder::new(
+                raw_writer,
                 bzip2::Compression::fast(),
-            )));
+            ))));
         }
         if ext.eq_ignore_ascii_case(std::ffi::OsStr::new("gz")) {
-            return Ok(Box::new(flate2::write::GzEncoder::new(
-                raw_reader,
+            return Ok(Box::new(io::BufWriter::new(flate2::write::GzEncoder::new(
+                raw_writer,
                 flate2::Compression::fast(),
-            )));
+            ))));
         }
         if ext.eq_ignore_ascii_case(std::ffi::OsStr::new("xz")) {
-            return Ok(Box::new(xz2::write::XzEncoder::new(raw_reader, 1)));
+            return Ok(Box::new(io::BufWriter::new(xz2::write::XzEncoder::new(
+                raw_writer, 1,
+            ))));
         }
     }
-    Ok(Box::new(raw_reader))
+    Ok(Box::new(io::BufWriter::new(raw_writer)))
 }
diff --git a/rustsat/src/instances/multiopt.rs b/rustsat/src/instances/multiopt.rs
index 41ca4a00..53ed0aa3 100644
--- a/rustsat/src/instances/multiopt.rs
+++ b/rustsat/src/instances/multiopt.rs
@@ -178,6 +178,10 @@ impl<VM: ManageVars> MultiOptInstance<VM> {
     }
 
     /// Writes the instance to a DIMACS MCNF file at a path
+    ///
+    /// # Performance
+    ///
+    /// For performance, consider using a [`std::io::BufWriter`] instance.
     pub fn to_dimacs_path<P: AsRef<Path>>(self, path: P) -> Result<(), io::Error> {
         let mut writer = fio::open_compressed_uncompressed_write(path)?;
         self.to_dimacs(&mut writer)
@@ -211,6 +215,10 @@ impl<VM: ManageVars> MultiOptInstance<VM> {
     }
 
     /// Writes the instance to an OPB file at a path
+    ///
+    /// # Performance
+    ///
+    /// For performance, consider using a [`std::io::BufWriter`] instance.
     pub fn to_opb_path<P: AsRef<Path>>(
         self,
         path: P,
diff --git a/rustsat/src/instances/opt.rs b/rustsat/src/instances/opt.rs
index 6bfb2608..84bbd64c 100644
--- a/rustsat/src/instances/opt.rs
+++ b/rustsat/src/instances/opt.rs
@@ -963,6 +963,10 @@ impl<VM: ManageVars> OptInstance<VM> {
     }
 
     /// Writes the instance to a DIMACS WCNF file at a path
+    ///
+    /// # Performance
+    ///
+    /// For performance, consider using a [`std::io::BufWriter`] instance.
     pub fn to_dimacs_path<P: AsRef<Path>>(self, path: P) -> Result<(), io::Error> {
         let mut writer = fio::open_compressed_uncompressed_write(path)?;
         self.to_dimacs(&mut writer)
@@ -996,6 +1000,10 @@ impl<VM: ManageVars> OptInstance<VM> {
     }
 
     /// Writes the instance to an OPB file at a path
+    ///
+    /// # Performance
+    ///
+    /// For performance, consider using a [`std::io::BufWriter`] instance.
     pub fn to_opb_path<P: AsRef<Path>>(
         self,
         path: P,
diff --git a/rustsat/src/instances/sat.rs b/rustsat/src/instances/sat.rs
index 244930aa..3a475205 100644
--- a/rustsat/src/instances/sat.rs
+++ b/rustsat/src/instances/sat.rs
@@ -710,6 +710,10 @@ impl<VM: ManageVars> SatInstance<VM> {
     }
 
     /// Writes the instance to a DIMACS CNF file at a path
+    ///
+    /// # Performance
+    ///
+    /// For performance, consider using a [`std::io::BufWriter`] instance.
     pub fn to_dimacs_path<P: AsRef<Path>>(self, path: P) -> Result<(), io::Error> {
         let mut writer = fio::open_compressed_uncompressed_write(path)?;
         self.to_dimacs(&mut writer)
@@ -742,6 +746,10 @@ impl<VM: ManageVars> SatInstance<VM> {
     }
 
     /// Writes the instance to an OPB file at a path
+    ///
+    /// # Performance
+    ///
+    /// For performance, consider using a [`std::io::BufWriter`] instance.
     pub fn to_opb_path<P: AsRef<Path>>(
         self,
         path: P,