Contribute a new experimental storage engine PSKIPLIST

[yjrobin]

Add a new experimental storage engine PSKIPLIST, contributed by 4Paradigm.

• PSKIPLIST is based on a persistent skiplist introduced in a VLDB21 paper worked with Dennis Wu (dennis.wu@intel.com).
• In order to re-use the code of the persistent skiplist in other projects of our own, we add our pskiplist repo as a submodule here.
• PSKIPLIST is still under development but we'd like to make this pull request as a start.
• Currently, only part of the UT are tested, we'll add more in the near future.
• Dennis will host a meeting for us to discuss more about this collaboration.

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This change is 

[KFilipek]

Add a new experimental storage engine PSKIPLIST, contributed by 4Paradigm.

* PSKIPLIST is based on a persistent skiplist introduced in a [VLDB21 paper](http://vldb.org/pvldb/vol14/p799-chen.pdf) worked with Dennis Wu ([dennis.wu@intel.com](mailto:dennis.wu@intel.com)).

* In order to re-use the code of the persistent skiplist in other projects of our own, we add our [pskiplist repo](https://github.com/4paradigm/pskiplist) as a submodule here.

* PSKIPLIST is still under development but we'd like to make this pull request as a start.

* Currently, only part of the UT are tested, we'll add more in the near future.

* Dennis will host a meeting for us to discuss more about this collaboration.

This change is 

Hi, thanks for your contribution!
According to the last point of your post, Igor will be available next week and then we can meet.
Could you adjust your PR to coding style rules? Without this GitHubActions cannot build your code. There is a command for code formatting:
link to contributing file

Best regards,
Krzysztof Filipek

[codecov]

Codecov Report

Merging #983 (09549a2) into master (63948c0) will increase coverage by 0.23%.
The diff coverage is 100.00%.

@@            Coverage Diff             @@
##           master     #983      +/-   ##
==========================================
+ Coverage   92.87%   93.10%   +0.23%     
==========================================
  Files          37       37              
  Lines        3368     3367       -1     
==========================================
+ Hits         3128     3135       +7     
+ Misses        240      232       -8     

Impacted Files	Coverage Δ
src/pmemobj_engine.h	92.30% <100.00%> (ø)
src/comparator/pmemobj_comparator.h	90.00% <0.00%> (+4.28%)	⬆️
src/iterator.h	50.00% <0.00%> (+50.00%)	⬆️
src/engine.h	100.00% <0.00%> (+100.00%)	⬆️

[yjrobin]

Hi Krzysztof,

Thanks for the tips. I've fixed the style issues.
Let's have the meeting next week. Talking to you soon.

Best rgds,
Jun Yang

[igchor]

Hi @yjrobin,

any update on this. Are you still interested in upstreaming your code?

[yjrobin]

Yes. I’m currently working on adding the single-writer-multiple-reader skiplist to the libpmemobj-cpp. Got other prioritized work to do in the past few months. Best rgds, Yang Jun

…

________________________________ From: Igor Chorążewicz ***@***.***> Sent: Tuesday, June 22, 2021 6:37:10 PM To: pmem/pmemkv ***@***.***> Cc: yjrobin ***@***.***>; Mention ***@***.***> Subject: Re: [pmem/pmemkv] Contribute a new experimental storage engine PSKIPLIST (#983) Hi @yjrobin<https://github.com/yjrobin>, any update on this. Are you still interested in upstreaming your code? — You are receiving this because you were mentioned. Reply to this email directly, view it on GitHub<#983 (comment)>, or unsubscribe<https://github.com/notifications/unsubscribe-auth/ANKGNO57M3DFEWOMC6XRCPLTUBRVNANCNFSM42OEH3NQ>.

[igchor]

Great! No rush, I just wanted to know if you're still interested. If you have any questions/problems regarding libpmemobj-cpp feel free to reach out.