Hi Stewart,

Great to hear from you! Awesome that you were able to find the code.

Thanks (at this point, some years later, also for introducing me to Eigen ;-) )
David

> On 8. Feb 2021, at 20:00, Stewart Martin-Haugh <[email protected]> 
> wrote:
> 
> Hi all,
> 
> I was David's supervisor for the GSOC project. I just found a local copy of 
> the code at CERN, which I have placed here:
> https://cernbox.cern.ch/index.php/s/SdtmgAsXasc9ttK 
> <https://cernbox.cern.ch/index.php/s/SdtmgAsXasc9ttK>
> in particular HermitianMatrix.h and HermitianBase.h 
> Best of luck!
> 
> Cheers,
> Stewart
> 
> 
> On Sun, 1 Nov 2020 at 15:11, Jens Wehner <[email protected] 
> <mailto:[email protected]>> wrote:
> Hello David,
> 
> any luck with the hermitian matrices?
> 
> Cheers Jens
> 
> | Jens Wehner, PhD | eScience Research Engineer | Email: 
> [email protected] 
> <https://outlook.office.com/mail/options/mail/[email protected]> | 
> Tel: +31(0)6 438 666 87 |
> | Netherlands eScience Center <https://www.esciencecenter.nl/> | Science Park 
> 140 | 1098 XG Amsterdam | The Netherlands |
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>  |
> 
> 
> 
> From: Rasmus Munk Larsen <[email protected] <mailto:[email protected]>>
> Sent: Friday, October 9, 2020 22:12
> To: eigen <[email protected] <mailto:[email protected]>>
> Subject: Re: [eigen] Hermitian matrices
>  
> Sorry, David :-( I hope you find it!
> 
> On Thu, Oct 8, 2020 at 2:37 PM David Tellenbach <[email protected] 
> <mailto:[email protected]>> wrote:
> Hi Jens,
> 
> Unfortunately I couldn't find it locally anymore and Bitbucket's Mercurial 
> repos aren't accessible anymore. There should be a copy somewhere (probably 
> Gaël has one in the pull request archive), I'll look around.
> 
> David
> 
>> On 8. Oct 2020, at 23:11, Jens Wehner <[email protected] 
>> <mailto:[email protected]>> wrote:
>> 
>> Hey David,
>> 
>> have you found the code?
>> 
>> I like the Hermitian matrix for the memory saving and for very nicely 
>> expressing physics in the datatype. I think the idea was to put it into the 
>> unsupported.
>> 
>> Cheers Jens
>> 
>> | Jens Wehner, PhD | eScience Research Engineer | Email: 
>> [email protected] 
>> <https://outlook.office.com/mail/options/mail/[email protected]> | 
>> Tel: +31(0)6 438 666 87 |
>> | Netherlands eScience Center <https://www.esciencecenter.nl/> | Science 
>> Park 140 | 1098 XG Amsterdam | The Netherlands |
>> | Twitter <https://twitter.com/eScienceCenter> | LinkedIn 
>> <https://www.linkedin.com/company/netherlands-escience-center> | Facebook 
>> <https://www.facebook.com/NLeScienceCenter/> | YouTube 
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>> <https://esciencecenter.us8.list-manage.com/subscribe/post?u=a0a563ca342f1949246a9f92f&id=31bfc2303d>
>>  |
>> 
>> 
>> From: David Tellenbach <[email protected] 
>> <mailto:[email protected]>>
>> Sent: Tuesday, October 6, 2020 20:36
>> To: [email protected] <mailto:[email protected]> 
>> <[email protected] <mailto:[email protected]>>
>> Subject: Re: [eigen] Hermitian matrices
>>  
>> @Rasmus, here are some benchmarks: 
>> https://listengine.tuxfamily.org/lists.tuxfamily.org/eigen/2018/08/msg00010.html
>>  
>> <https://listengine.tuxfamily.org/lists.tuxfamily.org/eigen/2018/08/msg00010.html>
>>  (scroll the the very end). As already said, Hermitian * Hermitian can give 
>> quite good performance and Dense * Hermitian doesn't really hurt. 
>> 
>>> On 6. Oct 2020, at 02:26, David Tellenbach <[email protected] 
>>> <mailto:[email protected]>> wrote:
>>> 
>>> IIRC it was in fact you who suggested using not a plain packed but a 
>>> rectangular full packed format ;-) 
>>> (https://software.intel.com/content/www/us/en/develop/documentation/mkl-developer-reference-c/top/lapack-routines/matrix-storage-schemes-for-lapack-routines.html#matrix-storage-schemes-for-lapack-routines_RFP_STORAGE
>>>  
>>> <https://software.intel.com/content/www/us/en/develop/documentation/mkl-developer-reference-c/top/lapack-routines/matrix-storage-schemes-for-lapack-routines.html#matrix-storage-schemes-for-lapack-routines_RFP_STORAGE>)
>>> 
>>> If this is worth definitely depends on the particular use-case. It has been 
>>> shown that a rectangular full packed format can be beneficial for e.g. 
>>> Cholesky (http://www.netlib.org/lapack/lawnspdf/lawn199.pdf 
>>> <http://citeseerx.ist.psu.edu/viewdoc/download?doi=10.1.1.214.102&rep=rep1&type=pdf>)
>>>  or Pade approximations 
>>> (https://pdfs.semanticscholar.org/86d2/28da4fc02672b2c990eb48a5a605c0e0360f.pdf
>>>  
>>> <https://pdfs.semanticscholar.org/86d2/28da4fc02672b2c990eb48a5a605c0e0360f.pdf>).
>>>  I published benchmark on this list and will try to dig them out. A 
>>> Hermitian*Hermitian product can be quite fast (you can basically fall back 
>>> to gemm for blocks in the RFP format) but Dense*Hermitian was not so good 
>>> if I remember correctly.
>>> 
>>> David
>>> 
>>>> On 6. Oct 2020, at 02:16, Rasmus Munk Larsen <[email protected] 
>>>> <mailto:[email protected]>> wrote:
>>>> 
>>>> David,
>>>> 
>>>> I can see that this might save 50% of memory by only storing the upper or 
>>>> lower triangle, and it would be nice to be able to automatically dispatch 
>>>> to faster eigensolvers etc. for Hermitian matrices. However, packed 
>>>> storage kernels are notoriously hard to optimize, and I wonder how much we 
>>>> would gain over the existing mechanism like SelfAdjointView?
>>>> 
>>>> https://eigen.tuxfamily.org/dox/classEigen_1_1SelfAdjointView.html\ 
>>>> <https://eigen.tuxfamily.org/dox/classEigen_1_1SelfAdjointView.html/>
>>>> 
>>>> Do you have some benchmark numbers for your patch?
>>>> 
>>>> Rasmus
>>>> 
>>>> On Mon, Oct 5, 2020 at 5:07 PM David Tellenbach 
>>>> <[email protected] <mailto:[email protected]>> 
>>>> wrote:
>>>> Hi Jens,
>>>> 
>>>> It would be great if you could finish this! I just saw that the patch is 
>>>> not accessible anymore, I'll see if I can find it.
>>>> 
>>>> Best,
>>>> David
>>>> 
>>>>> On 4. Oct 2020, at 21:27, Jens Wehner <[email protected] 
>>>>> <mailto:[email protected]>> wrote:
>>>>> 
>>>>> Thanks David,
>>>>> 
>>>>> I would probably like to give it a shot to brush up on my template 
>>>>> programming skills or lack thereof. 
>>>>> 
>>>>> Do you have the code somewhere public so I can have a look? If you have 
>>>>> time afterwards we can have a chat about the better implementation.
>>>>> 
>>>>> Cheers Jens
>>>>> 
>>>>> | Jens Wehner, PhD | eScience Research Engineer | Email: 
>>>>> [email protected] 
>>>>> <https://outlook.office.com/mail/options/mail/[email protected]> 
>>>>> | Tel: +31(0)6 438 666 87 |
>>>>> | Netherlands eScience Center <https://www.esciencecenter.nl/> | Science 
>>>>> Park 140 | 1098 XG Amsterdam | The Netherlands |
>>>>> | Twitter <https://twitter.com/eScienceCenter> | LinkedIn 
>>>>> <https://www.linkedin.com/company/netherlands-escience-center> | Facebook 
>>>>> <https://www.facebook.com/NLeScienceCenter/> | YouTube 
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>>>>> <https://esciencecenter.us8.list-manage.com/subscribe/post?u=a0a563ca342f1949246a9f92f&id=31bfc2303d>
>>>>>  |
>>>>> 
>>>>> 
>>>>> From: David Tellenbach <[email protected] 
>>>>> <mailto:[email protected]>>
>>>>> Sent: Sunday, October 4, 2020 0:16
>>>>> To: [email protected] <mailto:[email protected]> 
>>>>> <[email protected] <mailto:[email protected]>>
>>>>> Subject: Re: [eigen] Hermitian matrices
>>>>>  
>>>>> Hi Jens,
>>>>> 
>>>>> Yes, I've implemented support for Hermitian matrices as a Google Summer 
>>>>> of Code student in 2018 and finishing it is still somewhere on my 
>>>>> backlog. However, with today's knowledge the implementation should look 
>>>>> quite differently. If you are interested to work on this I'm happy to 
>>>>> discuss. Otherwise you will have to wait until I find some time to 
>>>>> reimplement it. This won't take me too long but without committing to 
>>>>> anything, I can already say that I won't find time before the beginning 
>>>>> of 2021.
>>>>> 
>>>>> Best,
>>>>> David
>>>>> 
>>>>>> On 2. Oct 2020, at 23:30, Jens Wehner <[email protected] 
>>>>>> <mailto:[email protected]>> wrote:
>>>>>> 
>>>>>> I recently discovered that David Tellenbach started/was in the 
>>>>>> middle/finished a 
>>>>>> 
>>>>>> Hermitian matrix class. 
>>>>>> http://manao.inria.fr/eigen_tmp/pullrequests/467/ 
>>>>>> <http://manao.inria.fr/eigen_tmp/pullrequests/467/>
>>>>>> I wanted to know what the status is and if any help is needed to push 
>>>>>> that along.
>>>>>> 
>>>>>> Cheers Jens
>>>>>> | Jens Wehner, PhD | eScience Research Engineer | Email: 
>>>>>> [email protected] 
>>>>>> <https://outlook.office.com/mail/options/mail/[email protected]>
>>>>>>  | Tel: +31(0)6 438 666 87 |
>>>>>> | Netherlands eScience Center <https://www.esciencecenter.nl/> | Science 
>>>>>> Park 140 | 1098 XG Amsterdam | The Netherlands |
>>>>>> | Twitter <https://twitter.com/eScienceCenter> | LinkedIn 
>>>>>> <https://www.linkedin.com/company/netherlands-escience-center> | 
>>>>>> Facebook <https://www.facebook.com/NLeScienceCenter/> | YouTube 
>>>>>> <https://www.youtube.com/channel/UCYLAIMi62d8tx3Ru6DOSPeg>  |  
>>>>>> Newsletter 
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>>>>>>  |
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