Subj : Re: Challenge: Multithreading & Synchronization
To   : comp.programming.threads
From : Uenal Mutlu
Date : Fri May 20 2005 03:58 pm

"Maciej Sobczak" wrote
>
> Uenal Mutlu wrote:
>
> > We've usually the following cases:
> [...]
>
> Really?
> What about the multithreaded program, where all threads use stdout to
> log their actions?
>
> puts("I'm doing this.");
> puts("I'm doing that.");
>
> Your idea of using the Lockable template breaks here, because there is
> nothing around that you could wrap with it.
>
> Which "case" would you apply here?

You have to ask yourself especially the following question:
  "which object(s) am I sharing among multiple threads?"
Then the solution will be simple.

> But anyway - all the cases you show are very specific to the operation
> with a single value object (some vector). This is not what happens in
> general.
>
> > // case1: exclusive access to an object:
> > void f()
> > {
> >   Locker L(vec.m);
> >   for (size_t i = 0; i < vec.size(); i++)
> >     {
> >        // manipulate vec
> >     }
> > }
>
> Let's say that I want to print the content of the vector to stdout. The
> above will not help me - I do not want other functions printing anything
> else in the middle (this might even crash the program).

It works. What do you think does "exclusive access to the object" mean?
Try this:

void f()
{
 Locker L(vec.m);
 for (size_t i = 0; i < vec.size(); i++)
   cout << vec[i].myfield << ...
}

.