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Re: Processor upgrade

 
 
nospam
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      05-12-2013
In article <(E-Mail Removed)>, Floyd L. Davidson
<(E-Mail Removed)> wrote:

> >Well, in my current machine during certain tasks the CPU load indicator
> >in the task manager goes to 100% for both cores and stays at 100% until
> >the task is completed. So I would assume that the processor is indeed
> >the bottleneck.

>
> With image processing that is fairly common, and indeed
> is probably the most annoying and longest waiting time
> when there is a noticeable bottleneck.


image processing is usually i/o bound, not cpu bound.

that's why photoshop users want the fastest disks they can get, as much
memory as they can get, etc.

video processing, on the other hand, is often cpu bound.

> The solution is not to look for the fastest CPU as such,
> but rather look for the chip with the most cores. Even
> if each core is half as fast as those on some other
> chip, the times when the speed of any one or two cores
> is the problem are rare. And when a process can be
> spread out over multiple cores... there ain't nothing
> like a pair of 6 core chips!


depends on the software. some software benefits from more cores and
other software does not.
 
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nospam
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      05-12-2013
In article <(E-Mail Removed)>, Floyd L. Davidson
<(E-Mail Removed)> wrote:

> >> >Well, in my current machine during certain tasks the CPU load indicator
> >> >in the task manager goes to 100% for both cores and stays at 100% until
> >> >the task is completed. So I would assume that the processor is indeed
> >> >the bottleneck.
> >>
> >> With image processing that is fairly common, and indeed
> >> is probably the most annoying and longest waiting time
> >> when there is a noticeable bottleneck.

> >
> >image processing is usually i/o bound, not cpu bound.
> >
> >that's why photoshop users want the fastest disks they can get, as much
> >memory as they can get, etc.

>
> If Photoshop users see it that way, they are wrong. If
> you spend any time at all editing an image, the editing
> time vastly out distances the time it takes to read and
> later write the image to disk.


photoshop users see a dramatic increase in performance when they have
more memory and faster hard drives. the cpu is *not* the bottleneck.

adobe has repeatedly said that to optimize photoshop to be as fast as
possible, give it fast drives and memory. they have a much better idea
than you do about its bottlenecks.

cpus have greatly increased in speed and the number of cores, but i/o
hasn't kept pace.

most image processing does simple calculations (e.g., adjust colour
balance) on a *lot* of pixels and moving them in and out of the cpu is
the bottleneck.

on the other hand, if you spend your days doing cpu intensive filters
such as radial blur, then it might be different but few people do that
more than occasionally, if they do at all.

> >video processing, on the other hand, is often cpu bound.

>
> And so is image editing in the way that I described above:
> the annoying waits that are noticed and frustrating.


nope. video editing involves more complex calculations, unless you're
doing something simple such as adjusting colour balance on all frames.
 
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nospam
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      05-12-2013
In article <(E-Mail Removed)>, Floyd L. Davidson
<(E-Mail Removed)> wrote:

> >> >> >Well, in my current machine during certain tasks the CPU load indicator
> >> >> >in the task manager goes to 100% for both cores and stays at 100% until
> >> >> >the task is completed. So I would assume that the processor is indeed
> >> >> >the bottleneck.
> >> >>
> >> >> With image processing that is fairly common, and indeed
> >> >> is probably the most annoying and longest waiting time
> >> >> when there is a noticeable bottleneck.
> >> >
> >> >image processing is usually i/o bound, not cpu bound.
> >> >
> >> >that's why photoshop users want the fastest disks they can get, as much
> >> >memory as they can get, etc.
> >>
> >> If Photoshop users see it that way, they are wrong. If
> >> you spend any time at all editing an image, the editing
> >> time vastly out distances the time it takes to read and
> >> later write the image to disk.

> >
> >photoshop users see a dramatic increase in performance when they have
> >more memory and faster hard drives. the cpu is *not* the bottleneck.
> >
> >adobe has repeatedly said that to optimize photoshop to be as fast as
> >possible, give it fast drives and memory. they have a much better idea
> >than you do about its bottlenecks.

>
> They understand, yes. YOU don't.


yes i do, and it's in agreement with adobe.

> Skip the fast hard
> drives, and add memory. If you have enough memory there
> will never be a wait, during editing, for a disk write,
> due to caching.


if you have enough memory, then you've removed the i/o bottleneck.
thanks for confirming it.

> >cpus have greatly increased in speed and the number of cores, but i/o
> >hasn't kept pace.
> >
> >most image processing does simple calculations (e.g., adjust colour
> >balance) on a *lot* of pixels and moving them in and out of the cpu is
> >the bottleneck.

>
> The CPU is the bottleneck.


photoshop's code is very highly optimized and is not the bottleneck,
except with certain filters such as radial blur that require a lot of
computation. the common stuff, like adjusting colour, exposure,
sharpening, etc. are all i/o bound.

long ago, the cpu was the bottleneck, but cpu performance has
dramatically increased, including offloading to the gpu, while memory
bandwidth has not kept pace. now the bottleneck is i/o.

i assume you're using the gimp, which is quite a bit slower than
photoshop doing the same operations, so i can see why you think image
processing is cpu bound.

> If the same simple
> calculation is done on 10 million pixels in sequence it
> takes ten times as long as it would to do that using 10
> cores to process 10 pixels at a time.


no it doesn't. there's always an overhead no matter how many cores you
have, and you will almost never realize a 10x improvement with 10
cores.

you also need 10x the memory bandwidth to keep all 10 cores fed with
data.
 
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Me
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      05-12-2013
On 13/05/2013 10:47 a.m., nospam wrote:
> In article <(E-Mail Removed)>, Floyd L. Davidson
> <(E-Mail Removed)> wrote:
>
>>>>>>> Well, in my current machine during certain tasks the CPU load indicator
>>>>>>> in the task manager goes to 100% for both cores and stays at 100% until
>>>>>>> the task is completed. So I would assume that the processor is indeed
>>>>>>> the bottleneck.
>>>>>>
>>>>>> With image processing that is fairly common, and indeed
>>>>>> is probably the most annoying and longest waiting time
>>>>>> when there is a noticeable bottleneck.
>>>>>
>>>>> image processing is usually i/o bound, not cpu bound.
>>>>>
>>>>> that's why photoshop users want the fastest disks they can get, as much
>>>>> memory as they can get, etc.
>>>>
>>>> If Photoshop users see it that way, they are wrong. If
>>>> you spend any time at all editing an image, the editing
>>>> time vastly out distances the time it takes to read and
>>>> later write the image to disk.
>>>
>>> photoshop users see a dramatic increase in performance when they have
>>> more memory and faster hard drives. the cpu is *not* the bottleneck.
>>>
>>> adobe has repeatedly said that to optimize photoshop to be as fast as
>>> possible, give it fast drives and memory. they have a much better idea
>>> than you do about its bottlenecks.

>>
>> They understand, yes. YOU don't.

>
> yes i do, and it's in agreement with adobe.
>
>> Skip the fast hard
>> drives, and add memory. If you have enough memory there
>> will never be a wait, during editing, for a disk write,
>> due to caching.

>
> if you have enough memory, then you've removed the i/o bottleneck.
> thanks for confirming it.
>
>>> cpus have greatly increased in speed and the number of cores, but i/o
>>> hasn't kept pace.
>>>
>>> most image processing does simple calculations (e.g., adjust colour
>>> balance) on a *lot* of pixels and moving them in and out of the cpu is
>>> the bottleneck.

>>
>> The CPU is the bottleneck.

>
> photoshop's code is very highly optimized and is not the bottleneck,
> except with certain filters such as radial blur that require a lot of
> computation. the common stuff, like adjusting colour, exposure,
> sharpening, etc. are all i/o bound.
>
> long ago, the cpu was the bottleneck, but cpu performance has
> dramatically increased, including offloading to the gpu, while memory
> bandwidth has not kept pace. now the bottleneck is i/o.
>
> i assume you're using the gimp, which is quite a bit slower than
> photoshop doing the same operations, so i can see why you think image
> processing is cpu bound.


That /was/ a big issue with the Gimp. It didn't utilise multi-core cpus
very well.
The newer versions do much better. The user may need to go into
Preferences|Environment|number of processors to use, and manually select
number of cores (including virtual cores).



>
>> If the same simple
>> calculation is done on 10 million pixels in sequence it
>> takes ten times as long as it would to do that using 10
>> cores to process 10 pixels at a time.

>
> no it doesn't. there's always an overhead no matter how many cores you
> have, and you will almost never realize a 10x improvement with 10
> cores.
>
> you also need 10x the memory bandwidth to keep all 10 cores fed with
> data.
>

This is all very nice, but PCs are terribly inefficient for image
processing compared to the dedicated processors in cameras, which manage
to perform complex operations (demosaicing raw data, complex
interpolation for automatic lens distortion and CA correction, colour
correction, encoding to jpeg etc) in the blink of an eye, and using very
little power.

 
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Wolfgang Weisselberg
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      05-15-2013
Floyd L. Davidson <(E-Mail Removed)> wrote:
> nospam <(E-Mail Removed)> wrote:


>>cpus have greatly increased in speed and the number of cores, but i/o
>>hasn't kept pace.


>>most image processing does simple calculations (e.g., adjust colour
>>balance) on a *lot* of pixels and moving them in and out of the cpu is
>>the bottleneck.


> The CPU is the bottleneck.


When the IO to the CPU is the bottleneck, then, yes, the CPU
is the bottleneck.

> If the same simple
> calculation is done on 10 million pixels in sequence it
> takes ten times as long as it would to do that using 10
> cores to process 10 pixels at a time.


How about a few 100 or even a couple 1000 cores? Called
graphic card ...

-Wolfgang
 
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