Hey guys,

We have just published another post on "Writing efficient numerical code in D", to Mir's Blog[1]. In this post we are focusing on mir.ndslice.algorithm usage in DCV[2], computer vision library that has recently joined libmir organization. We've had great success in optimizing DCV's algorithms mostly by replacing loop-style code with mir.ndslice.algorithm multidimensional iteration utilities[3], and we thought it was worth blogging about.

Any grammar (or any other type of) fix report is greatly appreciated!

Also, we'd like to ask Mike Parker to forward this to reddit if it's not too much trouble? :) Maybe only wait few days so we could weed out some mistakes from the text.

Cheers,
Relja

[1] http://blog.mir.dlang.io/ndslice/algorithm/optimization/2016/12/12/writing-efficient-numerical-code.html
[2] https://github.com/libmir/dcv
[3] https://github.com/libmir/dcv/pull/58

On Monday, 12 December 2016 at 21:58:23 UTC, Relja Ljubobratovic wrote:
> Hey guys,
>
> We have just published another post on "Writing efficient numerical code in D", to Mir's Blog[1].

Nice :)

Some comments:
- You can make the numbers in the table more readable by adding commas?
For example, 1624687 --> 1,624,687. Probably even better is to only show the most significant digits. 1624687 us --> 1.625 s for example.
- Add a sentence about the benchmarking set up. " The numbers shown are the best times of 10 trials, with LDC commandline options `ldc2 -O3 -release`" Something like that. Or add it to the configuration table.
- For the "convolution" example, could you elaborate on why the Mir-based implementation is so much faster than the C-like implementation? From the big table, I see that the speedup for DCV's convolution algorithms is not as large as 10x.
- The "threshold" algorithm has a 19x speed up?! (I would remove "threshold" from the average improvement calculation. The numbers are already awesome, no need to oversell it!)
- Overall, does this mean that DCV became more than twice as fast? How does it stack up to other vision libs after this massive speed boost?

cheers,
  Johan

On Monday, 12 December 2016 at 22:34:32 UTC, Johan Engelen wrote:
> On Monday, 12 December 2016 at 21:58:23 UTC, Relja Ljubobratovic wrote:
>> Hey guys,
>>
>> We have just published another post on "Writing efficient numerical code in D", to Mir's Blog[1].
>
> Nice :)

Thanks! :)

>
> Some comments:
> - You can make the numbers in the table more readable by adding commas?
> For example, 1624687 --> 1,624,687. Probably even better is to only show the most significant digits. 1624687 us --> 1.625 s for example.

Great suggestion - I was focusing on the speedup, so I didn't pay attention to run time, but obviously other people will.

> - Add a sentence about the benchmarking set up. " The numbers shown are the best times of 10 trials, with LDC commandline options `ldc2 -O3 -release`" Something like that. Or add it to the configuration table.

Thanks, will do. I agree there's an explanation missing on how benchmark is configured.

> - For the "convolution" example, could you elaborate on why the Mir-based implementation is so much faster than the C-like implementation? From the big table, I see that the speedup for DCV's convolution algorithms is not as large as 10x.

DCV's convolution is parallelized, which I believe, could be the reason. Ilya is probably the best man to elaborate the speedup vs C implementation.

> - The "threshold" algorithm has a 19x speed up?! (I would remove "threshold" from the average improvement calculation. The numbers are already awesome, no need to oversell it!)

I agree. I was thrilled when I saw the comparison at first, but to be honest, I'm not sure what's the main reason. Here's the commit diff if anyone is interested to explain:
https://github.com/libmir/dcv/pull/58/commits/0c744a7bb7308f07bd45d041c6e88e906c905fcf

> - Overall, does this mean that DCV became more than twice as fast? How does it stack up to other vision libs after this massive speed boost?

I'm not sure. But I'm afraid we're not even close to opencv, since its base image processing (and other) algorithms have been intensively (manually) optimized with SIMD, but also have almost 100% coverage with OpenCL (and CUDA from 3.x). Anyhow, I'd like not to bother with comparisons like this until we are satisfied with DCV - there's much work yet to be done, IMHO.

>
> cheers,
>   Johan

Thanks for the feedback Johan!

On 13/12/2016 11:34 AM, Johan Engelen wrote:
> On Monday, 12 December 2016 at 21:58:23 UTC, Relja Ljubobratovic wrote:
>> Hey guys,
>>
>> We have just published another post on "Writing efficient numerical
>> code in D", to Mir's Blog[1].
>
> Nice :)
>
> Some comments:
> - You can make the numbers in the table more readable by adding commas?
> For example, 1624687 --> 1,624,687. Probably even better is to only show
> the most significant digits. 1624687 us --> 1.625 s for example.

Oh underscores, then it is valid D!

On 12/12/16 4:58 PM, Relja Ljubobratovic wrote:
> Hey guys,
>
> We have just published another post on "Writing efficient numerical code
> in D", to Mir's Blog[1]. In this post we are focusing on
> mir.ndslice.algorithm usage in DCV[2], computer vision library that has
> recently joined libmir organization. We've had great success in
> optimizing DCV's algorithms mostly by replacing loop-style code with
> mir.ndslice.algorithm multidimensional iteration utilities[3], and we
> thought it was worth blogging about.
>
> Any grammar (or any other type of) fix report is greatly appreciated!
>
> Also, we'd like to ask Mike Parker to forward this to reddit if it's not
> too much trouble? :) Maybe only wait few days so we could weed out some
> mistakes from the text.
>
> Cheers,
> Relja
>
> [1]
> http://blog.mir.dlang.io/ndslice/algorithm/optimization/2016/12/12/writing-efficient-numerical-code.html
>
> [2] https://github.com/libmir/dcv
> [3] https://github.com/libmir/dcv/pull/58

This is awesome! Mike, could you please post to reddit about 11 hours from now if possible.

I'm about to fall asleep, but I made a quick pass through the piece. Here are a few nits:

* "In this post I’d like give" -> "This post gives"

* "module equipped with" -> "module that provides"

* "it’s usage" -> "its usage"

* "Note: It is assumed the reader is already somewhat familiar with ndslice package [1]." -> "This article assumes the reader has a cursory understanding of the ndslice package. If not, please consult this post/doc/webpage/etc before returning here."

* "What does it offer?" -> "What does mir.ndslice.algorithm offer?"

* "its integrated seamlessly" -> "it is integrated seamlessly"

* "by that allowing more natural flow of processing pipeline" -> "which makes for elegantly flowing processing pipelines"

* "One of key components to make code based" -> "One key component that makes code based"

* "LLVM based D compiler" -> "the LLVM based D compiler"

* "kernels you write" -> "computation kernels written by the end user"

* "else turned on" -> "turned on"

* ", by Johan Engelen" -> remove the comma

* "we’ve been actively refactoring" -> define the team; so far the article referred to the author as a single person

* "with mir.ndslice.algorithm equivalent" -> "with mir.ndslice.algorithm equivalents"

* align numbers in html tables to the right

* "As you can see, speedups" -> "Speedups"

* "as I’ll show you in this post" -> "as shown below"

* "take a look at PR" -> "take a look at the pull request"

* "Discalmer" -> "Disclaimer"

* "mind DCV project" -> "mind the DCV project"

* "showing power" -> "showing the power"

* "dive into implementation" -> "dive into the implementation"

* "without extensive optimization techniques applied" -> "without extensive optimizations"

* "In future we’ll focus" -> "A future post will focus"

* "first we’ll take a look" -> "first let's take a look"

* "basic principle how it can efficiently replace loop-based code" -> "basic principle of replacing loop-based code with pipelines efficiently"

* "… This code" -> "This code"

* "apply given kernel" -> "apply the given kernel"

* "To bring this example more down to earth" -> "To make the example more concrete"

* "As you can see, we are replacing" -> "The pipeline version replaces"

* "with few magic calls" -> "with a few magic calls"

* "And as you may have noticed, at" -> "At"

* "I get ~10x speedup" -> there's been a bunch of "we" and now getting back to "I" is surprising. You may want to make a pass making sure the use of person is consistent.

* "that variant written" -> "that the variant written"

* "syntax, and are" -> "syntax and are"

* "this is most basic binarization" -> "this is a most basic binarization"

* "Special part to care about, related to lockstep, is that byElement call on each input Slice" -> "The call to byElement inside lockstep is worth special attention"

* "We can notice right away there’s a change" -> "First off, there's a change"

* "requires this so" -> "assumes that is the case"

* "We can also notice byElement" -> "Notably, byElement"

* "examine performance differences" -> "compare the impact of these changes on performance"

* "On my machine" -> "On a Core i7 laptop with xyz GB or RAM and xyz other relevant parameters..."

* "result is following" -> "the results are as follows"

* "with very little effort using" -> "with very little effort by using"

* "and it’s submodules" -> "and its submodules"

* "coming for some numerical computing" -> "having an interest in numerical computing"

* "would have to be introduced to ndslice" -> "should take a close look at ndslice"

I suggest making two passes through the piece: (a) one pass should reduce fillers that are abundant ("as you can see", "as I'll show you", "as said in the docs"...) A few are fine (perhaps 2-3 in the whole article. Then (b) one pass looking for unified use of "I" (most likely: the author, use sparingly), "you" (the reader, use sparingly), and "we" (most likely: the author and reader looking together at something).

The results are terrific, congrats Ilya and Relja!


Andrei

On Tuesday, 13 December 2016 at 05:27:01 UTC, Andrei Alexandrescu wrote:
>
> I'm about to fall asleep, but I made a quick pass through the piece. Here are a few nits:

Thanks for an extensive feedback, Andrei! I've followed up 99% of fixes given here[1], but unfortunately I'll be unavailable for the rest of the day, so I'm passing the torch (or the hot potato) to Ilya.

>
> * "we’ve been actively refactoring" -> define the team; so far the article referred to the author as a single person
I've done the coding, but couldn't have done it without Ilya's consulting, so I put the 'Mir team' there. Hope thats ok.

>
> * "On my machine" -> "On a Core i7 laptop with xyz GB or RAM and xyz other relevant parameters..."

There are specs shown at the top of the post, so I thought it would be best just to remove the "On my machine part". Again, I hope that's alright.

>
> I suggest making two passes through the piece: (a) one pass should reduce fillers that are abundant ("as you can see", "as I'll show you", "as said in the docs"...) A few are fine (perhaps 2-3 in the whole article. Then (b) one pass looking for unified use of "I" (most likely: the author, use sparingly), "you" (the reader, use sparingly), and "we" (most likely: the author and reader looking together at something).

As I've demonstrated, I'm quite unexperienced with writing. :) So, thanks for the feedback, I've learned a lot! If I catch some time during the day, I'll be sure to take another glance at it!

>
> The results are terrific, congrats Ilya and Relja!
>
>
> Andrei

Thanks a lot Andrei!
Relja

[1] https://github.com/libmir/blog/pull/32

On Monday, 12 December 2016 at 21:58:23 UTC, Relja Ljubobratovic wrote:
> http://blog.mir.dlang.io/ndslice/algorithm/optimization/2016/12/12/writing-efficient-numerical-code.html

Awesome!

On Tuesday, 13 December 2016 at 05:27:01 UTC, Andrei Alexandrescu wrote:

>
> This is awesome! Mike, could you please post to reddit about 11 hours from now if possible.

Yes, I intend to post it to both reddit and FB, but it will have to be a couple of hours earlier than that (Korea is UTC+9).

On Tuesday, 13 December 2016 at 09:58:09 UTC, Mike Parker wrote:
> On Tuesday, 13 December 2016 at 05:27:01 UTC, Andrei Alexandrescu wrote:
>
>>
>> This is awesome! Mike, could you please post to reddit about 11 hours from now if possible.
>
> Yes, I intend to post it to both reddit and FB, but it will have to be a couple of hours earlier than that (Korea is UTC+9).

https://www.reddit.com/r/programming/comments/5i42vc/writing_efficient_numerical_code_in_d/

On Tuesday, 13 December 2016 at 15:31:00 UTC, Mike Parker wrote:
https://www.reddit.com/r/programming/comments/5i42vc/writing_efficient_numerical_code_in_d/

Thank you, Mike!