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[uforob]

I wrote a code that would be like the one attached but i obtain wrong results. The question are

- for some reason is it better or correct inverting blocks inserting do nothing in the "else" block?

- what's the effect of inlcuding sinchronization instructions inside a block of a conditional?

if(...) { //do nothing } else { //do something ... barrier(CLK_LOCAL_MEM_FENCE); .... barrier(CLK_LOCAL_MEM_FENCE); }

[pulec]

ad 1) May I ask why don't you just invert the condition and put the "do something" into the if-block? (And omit the else block)? It is not an error, but I think it'd be better.
If the results are wrong, don't you also need global memory synchronisation?
ad 2) The OpenCL specification:
"If barrier is inside a conditional statement, then all
work-items must enter the conditional if any work-item
enters the conditional statement and executes the
barrier."
So it is dangerous to do that unless you know that either all or none of the work-items enters the block with the barrier.
EDIT: The work-items are meant work-items inside one work-group.

[himanshu_gautam]

From OpenCL Spec 1.1:

If barrier is inside a conditional statement, then all
work-items must enter the conditional if any work-item
enters the conditional statement and executes the
barrier.
If barrer is inside a loop, all work-items must execute
the barrier for each iteration of the loop before any are
allowed to continue execution beyond the barrier.

Edit: Sorry.I missed the comment from pulec.