From 8d330b5e63260aa21f1730fd57430cc3f506e4df Mon Sep 17 00:00:00 2001
From: porcuquine <porcuquine@users.noreply.github.com>
Date: Wed, 1 Jul 2020 09:03:08 -0700
Subject: [PATCH] Allocate less.

---
 filecoin-proofs/src/api/seal.rs               | 19 +++----------------
 .../porep/src/stacked/vanilla/proof.rs        |  7 ++++---
 2 files changed, 7 insertions(+), 19 deletions(-)

diff --git a/filecoin-proofs/src/api/seal.rs b/filecoin-proofs/src/api/seal.rs
index b3538b5b5b..9b9efecb22 100644
--- a/filecoin-proofs/src/api/seal.rs
+++ b/filecoin-proofs/src/api/seal.rs
@@ -1,6 +1,5 @@
 use std::fs::{self, metadata, File, OpenOptions};
 use std::io::prelude::*;
-use std::io::BufWriter;
 use std::path::{Path, PathBuf};
 
 use anyhow::{ensure, Context, Result};
@@ -780,24 +779,12 @@ pub fn fauxrep_aux<
     cache_path: R,
     out_path: S,
 ) -> Result<Commitment> {
-    let sector_bytes = PaddedBytesAmount::from(porep_config).0 as usize;
+    let sector_bytes = PaddedBytesAmount::from(porep_config).0;
 
     {
         // Create a sector full of null bytes at `out_path`.
-        let chunk_size = usize::min(sector_bytes, 1024);
-        let chunk = vec![0; chunk_size];
-        let chunk_count = sector_bytes / chunk_size;
-        assert_eq!(
-            0,
-            sector_bytes % chunk_size,
-            "sector size is not an even number of KiB"
-        );
-
         let file = File::create(&out_path)?;
-        let mut buf = BufWriter::with_capacity(chunk.len(), file);
-        for _ in 0..chunk_count {
-            buf.write_all(&chunk)?;
-        }
+        file.set_len(sector_bytes)?;
     }
 
     let fake_comm_c = <Tree::Hasher as Hasher>::Domain::random(&mut rng);
@@ -805,7 +792,7 @@ pub fn fauxrep_aux<
         fake_comm_c,
         out_path,
         &cache_path,
-        sector_bytes,
+        sector_bytes as usize,
     )?;
 
     let p_aux_path = cache_path.as_ref().join(CacheKey::PAux.to_string());
diff --git a/storage-proofs/porep/src/stacked/vanilla/proof.rs b/storage-proofs/porep/src/stacked/vanilla/proof.rs
index 48fd7bc30f..fe7ac93dca 100644
--- a/storage-proofs/porep/src/stacked/vanilla/proof.rs
+++ b/storage-proofs/porep/src/stacked/vanilla/proof.rs
@@ -1194,17 +1194,18 @@ impl<'a, Tree: 'static + MerkleTreeTrait, G: 'static + Hasher> StackedDrg<'a, Tr
             )
             .expect("failed to create TreeBuilder");
 
+            // Allocate zeros once and reuse.
+            let zero_leaves: Vec<Fr> = vec![Fr::zero(); max_gpu_tree_batch_size];
             for (i, config) in configs.iter().enumerate() {
                 let mut consumed = 0;
                 while consumed < nodes_count {
                     let batch_size = usize::min(max_gpu_tree_batch_size, nodes_count - consumed);
-                    let zero_leaves: Vec<Fr> = vec![Fr::zero(); batch_size];
 
                     consumed += batch_size;
 
                     if consumed != nodes_count {
                         tree_builder
-                            .add_leaves(zero_leaves.as_slice())
+                            .add_leaves(&zero_leaves[0..batch_size])
                             .expect("failed to add leaves");
                         continue;
                     };
@@ -1217,7 +1218,7 @@ impl<'a, Tree: 'static + MerkleTreeTrait, G: 'static + Hasher> StackedDrg<'a, Tr
                     );
 
                     let (_, tree_data) = tree_builder
-                        .add_final_leaves(&zero_leaves)
+                        .add_final_leaves(&zero_leaves[0..batch_size])
                         .expect("failed to add final leaves");
                     let tree_data_len = tree_data.len();
                     let cache_size = get_merkle_tree_cache_size(