Do I have to use threads?

[Philip Semanchuk]

On Jan 7, 2010, at 11:32 AM, Jorgen Grahn wrote:

> On Thu, 2010-01-07, Marco Salden wrote:
>> On Jan 6, 5:36 am, Philip Semanchuk <phi... at semanchuk.com> wrote:
>>> On Jan 5, 2010, at 11:26 PM, aditya shukla wrote:
>>>
>>>> Hello people,
>>>
>>>> I have 5 directories corresponding 5  different urls .I want to
>>>> download
>>>> images from those urls and place them in the respective
>>>> directories.I have
>>>> to extract the contents and download them simultaneously.I can
>>>> extract the
>>>> contents and do then one by one. My questions is for doing it
>>>> simultaneously
>>>> do I have to use threads?
>>>
>>> No. You could spawn 5 copies of wget (or curl or a Python program  
>>> that
>>> you've written). Whether or not that will perform better or be  
>>> easier
>>> to code, debug and maintain depends on the other aspects of your
>>> program(s).
>>>
>>> bye
>>> Philip
>>
>> Yep, the more easier and straightforward the approach, the better:
>> threads are always (programmers')-error-prone by nature.
>> But my question would be: does it REALLY need to be simultaneously:
>> the CPU/OS only has more overhead doing this in parallel with
>> processess. Measuring sequential processing and then trying to
>> optimize (e.g. for user response or whatever) would be my prefered  
>> way
>> to go. Less=More.
>
> Normally when you do HTTP in parallell over several TCP sockets, it
> has nothing to do with CPU overhead. You just don't want every GET to
> be delayed just because the server(s) are lazy responding to the first
> few ones; or you might want to read the text of a web page and the CSS
> before a few huge pictures have been downloaded.
>
> His "I have to [do them] simultaneously" makes me want to ask "Why?".

Exactly what I was thinking. He's surely doing something more  
complicated than his post suggests, and without that detail it's  
impossible to say whether threads, processes, asynch or voodoo is the  
best approach.


bye
P