Re: Parfor loop interdependencies

[Matthias Boehm]

ok thanks for catching this Mike - I just gave it a try and the new IPA
propagated scalars into this function, which allowed for constant folding
of the indexing expressions, and effectively hid the underlying issue. With
disabled IPA, I'm able to reproduce this issue. Interestingly, it only
shows up in spark but not hadoop execution modes.

Regards,
Matthias

On Fri, Jun 16, 2017 at 5:35 PM,  wrote:

> On the latest master, versus the one from a few days ago, this issue
> appears to be "fixed".  The code is in PR 542, and the for-loop in the
> `nn/layers/conv2d_depthwise.dml::forward` function was the one that was
> previously resulting in null pointer exceptions when forced as a parfor
> loop.  The `check=0` is still needed, but the null pointer is no longer
> being thrown.
>
> --
>
> Mike Dusenberry
> GitHub: github.com/dusenberrymw
> LinkedIn: linkedin.com/in/mikedusenberry
>
> Sent from my iPhone.
>
>
> > On Jun 14, 2017, at 9:08 PM, Matthias Boehm 
> wrote:
> >
> > Generally, the parfor dependency analysis applies a series of tests
> > including traditional techniques from high-performance compilers combined
> > with additional rules for common cases. This dependency analysis tries to
> > proof that there are no loop-carried dependencies - so yes, false
> positives
> > can happen, in which case a user needs to take responsibility by
> disabling
> > the dependency analysis.
> >
> > Regarding your concrete problem - any null pointer exception is of course
> > bug and needs fixing. Could you please create a minimal scenario that
> > reproduces this issues and create a JIRA for it. I'm happy to help
> > resolving this.
> >
> > Regards,
> > Matthias
> >
> >> On Wed, Jun 14, 2017 at 4:24 PM,  wrote:
> >>
> >> While working on depthwise convolution, I wanted to make use of a parfor
> >> loop to run multiple convolutions at once (there is a vectorized
> approach
> >> as well, but that is out of scope for this question), but I'm running
> into
> >> issues with false flags for loop interdependencies.  Within the parfor
> >> body, I am performing left-indexing over unique ranges to store results
> in
> >> a variable `out`, and the engine currently expresses concerns regarding
> >> this variable.  The range bounds are short expressions, and I have
> printed
> >> out the ranges to be absolutely sure that they are unique.  If I use
> >> `check=0`, then the engine dies with a null pointer exception.
> >>
> >> What is the current strategy used for determining inter-loop
> dependencies
> >> for parfor statements?  How can we improve this?
> >>
> >> -Mike
> >>
> >> --
> >>
> >> Mike Dusenberry
> >> GitHub: github.com/dusenberrymw
> >> LinkedIn: linkedin.com/in/mikedusenberry
> >>
> >> Sent from my iPhone.
> >>
> >>
>

Re: Parfor loop interdependencies

[Matthias Boehm]

Generally, the parfor dependency analysis applies a series of tests
including traditional techniques from high-performance compilers combined
with additional rules for common cases. This dependency analysis tries to
proof that there are no loop-carried dependencies - so yes, false positives
can happen, in which case a user needs to take responsibility by disabling
the dependency analysis.

Regarding your concrete problem - any null pointer exception is of course
bug and needs fixing. Could you please create a minimal scenario that
reproduces this issues and create a JIRA for it. I'm happy to help
resolving this.

Regards,
Matthias

On Wed, Jun 14, 2017 at 4:24 PM,  wrote:

> While working on depthwise convolution, I wanted to make use of a parfor
> loop to run multiple convolutions at once (there is a vectorized approach
> as well, but that is out of scope for this question), but I'm running into
> issues with false flags for loop interdependencies.  Within the parfor
> body, I am performing left-indexing over unique ranges to store results in
> a variable `out`, and the engine currently expresses concerns regarding
> this variable.  The range bounds are short expressions, and I have printed
> out the ranges to be absolutely sure that they are unique.  If I use
> `check=0`, then the engine dies with a null pointer exception.
>
> What is the current strategy used for determining inter-loop dependencies
> for parfor statements?  How can we improve this?
>
> -Mike
>
> --
>
> Mike Dusenberry
> GitHub: github.com/dusenberrymw
> LinkedIn: linkedin.com/in/mikedusenberry
>
> Sent from my iPhone.
>
>

Parfor loop interdependencies

[dusenberrymw]

While working on depthwise convolution, I wanted to make use of a parfor loop 
to run multiple convolutions at once (there is a vectorized approach as well, 
but that is out of scope for this question), but I'm running into issues with 
false flags for loop interdependencies.  Within the parfor body, I am 
performing left-indexing over unique ranges to store results in a variable 
`out`, and the engine currently expresses concerns regarding this variable.  
The range bounds are short expressions, and I have printed out the ranges to be 
absolutely sure that they are unique.  If I use `check=0`, then the engine dies 
with a null pointer exception.

What is the current strategy used for determining inter-loop dependencies for 
parfor statements?  How can we improve this?

-Mike

--

Mike Dusenberry
GitHub: github.com/dusenberrymw
LinkedIn: linkedin.com/in/mikedusenberry

Sent from my iPhone.