From 0244439006529b11cac7b9a3d0156087ae1657ea Mon Sep 17 00:00:00 2001
From: Sergei Isakov <iserge@google.com>
Date: Mon, 6 Jul 2020 19:40:15 +0200
Subject: [PATCH] Add measurement gate. Comment.

---
 lib/parfor.h | 3 +++
 1 file changed, 3 insertions(+)

diff --git a/lib/parfor.h b/lib/parfor.h
index 99643a7e..a135fa4c 100644
--- a/lib/parfor.h
+++ b/lib/parfor.h
@@ -25,6 +25,9 @@ namespace qsim {
 
 template <uint64_t MIN_SIZE>
 struct ParallelForT {
+  // GetIndex0 and GetIndex1 are useful when we need to know how work was
+  // divided between threads, for instance, for reusing partial sums obtained
+  // by RunReduceP.
   static uint64_t GetIndex0(
       uint64_t size, unsigned num_threads, unsigned thread_id) {
     return size >= MIN_SIZE ? size * thread_id / num_threads : 0;