On 2017/05/09 16:48:12 +0800, Junchang Wang wrote:
> Oops. Forgot the summary in previous email. Resend the patch.
>
>
> The Answer to Quick Quiz 5.27 is a bit hard to follow. Rewrite it.
>
> Signed-off-by: Junchang Wang <junchangwang@xxxxxxxxx>
> ---
> count/count.tex | 14 +++++++-------
> 1 file changed, 7 insertions(+), 7 deletions(-)
>
> diff --git a/count/count.tex b/count/count.tex
> index cc47554..6dfc7a6 100644
> --- a/count/count.tex
> +++ b/count/count.tex
> @@ -1258,13 +1258,13 @@ machine.
> fast and scalable while allowing readers to also enjoy
> reasonable performance and scalability?
> \QuickQuizAnswer{
> - One approach would be to maintain a global approximation
> - to the value.
> - Readers would increment their per-thread variable, but when it
> - reached some predefined limit, atomically add it to a global
> - variable, then zero their per-thread variable.
> - This would permit a tradeoff between average increment overhead
> - and accuracy of the value read out.
> + One approach would be to add a global variable maintaining a
> + approximation to the exact value. An updater would increment its
> + per-thread variable, and when its value reaches predefined limit,
> + atomically add the value to the global variable, then zero its
> + per-thread variable. Readers simply return the value of global variable,
> + enjoying reasonable performance. This would permit a tradeoff between
> + average increment overhead and accuracy of the value read out.
>
> The reader is encouraged to think up and try out other approaches,
> for example, using a combining tree.
>
Hi Junchang,
What confused you seems to be a simple typo.
Isn't the following one-liner sufficient for you?
Thanks, Akira
--8<---->8--
>From 725b32938e0cbc245e5a528fd475951bb8be1de5 Mon Sep 17 00:00:00 2001
From: Akira Yokosawa <akiyks@xxxxxxxxx>
Date: Tue, 9 May 2017 23:39:57 +0900
Subject: [PATCH] count: Fix typo in Answer to Quick Quiz 5.27
Reported-by: Junchang Wang <junchangwang@xxxxxxxxx>
Signed-off-by: Akira Yokosawa <akiyks@xxxxxxxxx>
---
count/count.tex | 2 +-
1 file changed, 1 insertion(+), 1 deletion(-)
diff --git a/count/count.tex b/count/count.tex
index cc47554..096b53d 100644
--- a/count/count.tex
+++ b/count/count.tex
@@ -1260,7 +1260,7 @@ machine.
\QuickQuizAnswer{
One approach would be to maintain a global approximation
to the value.
- Readers would increment their per-thread variable, but when it
+ Updaters would increment their per-thread variable, but when it
reached some predefined limit, atomically add it to a global
variable, then zero their per-thread variable.
This would permit a tradeoff between average increment overhead
--
2.7.4
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