[firedrake] PP14 slides

[Kelly, Paul H J]

Hi Lawrence

slide 7 - if you want to show that image it needs to fill the slide.

(people don't notice if you occasionally turn off the background, the top and bottom bars etc).

slide 8 - consider using blank lines and perhaps even comments, to clarify structure (I hope you will point to lines of code to explain what is going on - so you need the bits separated.
I like to say that FFC "weaves" the weak form of the PDE with the function space specifications (in the "aspect oriented programming" sense of the word weave).
This helps clarify that the tool is precise, "do what I say", it doesn't make up any details of what is to be calculated.

slide 11 "for each ele" but there is no ele - ah OK....

slide 11 it's unclear whether "count" is a user-chosen identifier or a PyOP thing to say it's a counter (maybe this even applies to the other variable names).

slide 11-12 people often ask why we can't *analyse* the kernels to determine the access descriptors - why do we impose the ugly burden of spelling them out?
In contrast, the Liszt people require the mesh to be accessed via getters and setters, and they statically analyse the kernel to track them all down - to compute what they call the "stencil of the kernel".
This is a different point in the design space with different tradeoffs.  They *still* require access to the mesh to be abstract - ie via getters and setters.  We hide all details of the mesh representation from the kernel - there is no explicit dereferencing of a map/pointer in the kernel.  We say the access descriptors belong to the loop, they say the stencil belongs to the kernel.

There are fairly good arguments on both sides :)

Slide 16 - consider merging this with slide 15 so you can point to the picture.

Slide 21 "stream bandwidth" - you need words on the slide to clarify that you mean the well-know STREAM bnchmark?

Slide 22 - how many layers in this experiment?
(you have 8 threads but show perf only up to 4?)

Slide 23 - the L3 cache bandwidth at 4 threads appears to match the STREAM bandwidth (is this for a well-ordered mesh?)

Slide 25 - *valuable bandwidth* reaches 82% of STREAM.

Is the title right, given the actual content of the talk?

Best wishes

Paul

On 13 Feb 2014, at 17:36, Lawrence Mitchell wrote:

Hi folks,

I've attached the current PP14 slides, they're also at bitbucket.org/mapdes/pp14<http://bitbucket.org/mapdes/pp14>.

The author list is the one for the mini symposium, please shout if you feel left out.

All suggestions gratefully received.  Presentation is not til Friday next week so I will probably make further alterations.

Lawrence

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