From e92fd0f9b293b0a23f61df5e4d4d3e2a2627dfd6 Mon Sep 17 00:00:00 2001
From: Jeffrey Walton <noloader@gmail.com>
Date: Mon, 2 Apr 2018 13:40:33 -0400
Subject: [PATCH] Hoist XY and V out of parallel for loop

---
 scrypt.cpp | 19 ++++---------------
 1 file changed, 4 insertions(+), 15 deletions(-)

diff --git a/scrypt.cpp b/scrypt.cpp
index 452ec284..34b0532f 100644
--- a/scrypt.cpp
+++ b/scrypt.cpp
@@ -251,34 +251,23 @@ size_t Scrypt::DeriveKey(byte*derived, size_t derivedLen, const byte*secret, siz
     // 1: (B_0 ... B_{p-1}) <-- PBKDF2(P, S, 1, p * MFLen)
     PBKDF2_SHA256(B, B.size(), secret, secretLen, salt, saltLen, 1);
 
-    if (parallel == 1)
+    // http://stackoverflow.com/q/49604260/608639
+    #pragma omp parallel
     {
         AlignedSecByteBlock XY(static_cast<size_t>(blockSize * 256U));
         AlignedSecByteBlock  V(static_cast<size_t>(blockSize * cost * 128U));
 
         // 2: for i = 0 to p - 1 do
-        // 3: B_i <-- MF(B_i, N)
-        Smix(B, static_cast<size_t>(blockSize), cost, V, XY);
-        XY.SetMark(256); V.SetMark(128);
-    }
-    else
-    {
-        // 2: for i = 0 to p - 1 do
-        #pragma omp parallel for
+        #pragma omp for
         for (size_t i = 0; i < static_cast<size_t>(parallel); ++i)
         {
-            // Can't figure out how to hoist this out of the for-loop
-            //   https://stackoverflow.com/q/49604260/608639
-            AlignedSecByteBlock XY(static_cast<size_t>(blockSize * 256U));
-            AlignedSecByteBlock  V(static_cast<size_t>(blockSize * cost * 128U));
-
             // 3: B_i <-- MF(B_i, N)
             const ptrdiff_t offset = static_cast<ptrdiff_t>(blockSize*i*128);
             Smix(B+offset, static_cast<size_t>(blockSize), cost, V, XY);
-            XY.SetMark(256); V.SetMark(128);
         }
     }
 
+
     // 5: DK <-- PBKDF2(P, B, 1, dkLen)
     PBKDF2_SHA256(derived, derivedLen, secret, secretLen, B, B.size(), 1);