[PATCH] Update Answer to Quick Quiz 5.27

[PATCH] Update Answer to Quick Quiz 5.27

[Junchang Wang]

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@gmail.com>
---
 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.
-- 
2.7.4

Re: [PATCH] Update Answer to Quick Quiz 5.27

[Akira Yokosawa]

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@gmail.com>
> ---
>  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@gmail.com>
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@gmail.com>
Signed-off-by: Akira Yokosawa <akiyks@gmail.com>
---
 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

Re: [PATCH] Update Answer to Quick Quiz 5.27

[Junchang Wang]

Hi Akira,

That's the major point. Fair enough :-)


Thanks,
--Jason


On Tue, May 9, 2017 at 10:56 PM, Akira Yokosawa <akiyks@gmail.com> wrote:
> 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@gmail.com>
>> ---
>>  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@gmail.com>
> 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@gmail.com>
> Signed-off-by: Akira Yokosawa <akiyks@gmail.com>
> ---
>  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
>
>

Re: [PATCH] Update Answer to Quick Quiz 5.27

[Akira Yokosawa]

On 2017/05/09 23:21:33 +0800, Junchang Wang wrote:
> Hi Akira,
> 
> That's the major point. Fair enough :-)
> 

So, are you OK with me submitting the patch with your Acked-by?

                      Thanks, Akira
> 
> Thanks,
> --Jason
> 
> 
> On Tue, May 9, 2017 at 10:56 PM, Akira Yokosawa <akiyks@gmail.com> wrote:
>> 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@gmail.com>
>>> ---
>>>  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@gmail.com>
>> 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@gmail.com>
>> Signed-off-by: Akira Yokosawa <akiyks@gmail.com>
>> ---
>>  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
>>
>>
> 

Re: [PATCH] Update Answer to Quick Quiz 5.27

[Junchang Wang]

Hi Akira,

Sure. Please go ahead. Thanks a lot.


--Jason


On Wed, May 10, 2017 at 6:38 AM, Akira Yokosawa <akiyks@gmail.com> wrote:
> On 2017/05/09 23:21:33 +0800, Junchang Wang wrote:
>> Hi Akira,
>>
>> That's the major point. Fair enough :-)
>>
>
> So, are you OK with me submitting the patch with your Acked-by?
>
>                       Thanks, Akira
>>
>> Thanks,
>> --Jason
>>
>>
>> On Tue, May 9, 2017 at 10:56 PM, Akira Yokosawa <akiyks@gmail.com> wrote:
>>> 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@gmail.com>
>>>> ---
>>>>  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@gmail.com>
>>> 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@gmail.com>
>>> Signed-off-by: Akira Yokosawa <akiyks@gmail.com>
>>> ---
>>>  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
>>>
>>>
>>
>

[PATCH] count: Fix typo in Answer to Quick Quiz 5.27

[Akira Yokosawa]

From 557aa593d97bf2b8cc47ff14fbcaf3f80703866a Mon Sep 17 00:00:00 2001
From: Akira Yokosawa <akiyks@gmail.com>
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@gmail.com>
Signed-off-by: Akira Yokosawa <akiyks@gmail.com>
Acked-by: Junchang Wang <junchangwang@gmail.com>
---
 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

Re: [PATCH] count: Fix typo in Answer to Quick Quiz 5.27

[Paul E. McKenney]

On Thu, May 11, 2017 at 09:47:58AM +0900, Akira Yokosawa wrote:
> >From 557aa593d97bf2b8cc47ff14fbcaf3f80703866a Mon Sep 17 00:00:00 2001
> From: Akira Yokosawa <akiyks@gmail.com>
> 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@gmail.com>
> Signed-off-by: Akira Yokosawa <akiyks@gmail.com>
> Acked-by: Junchang Wang <junchangwang@gmail.com>

Queued and pushed, thank you both!

							Thanx, Paul

> ---
>  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
> 
>