[Paraview] [EXTERNAL] Re: Comparison of Visit and ParaView development

[Scott, W Alan]

Paul,
I looked at a few of the bugs listed below.  

I replicated 15944, this would impact my users.  It's on Sandia's list.  

13802 works correctly on 5.0.1.  Note that you are creating 2.6 billion cells, and from what I can tell, you are running out of memory on your server side.  I was able to get this to work with 8 nodes of a cluster.  Try running the View/ Memory Inspector, it will tell you how much pressure you are putting on your memory.

Alan



-----Original Message-----
From: ParaView [mailto:paraview-bounces at paraview.org] On Behalf Of Paul Melis
Sent: Thursday, June 16, 2016 2:52 AM
To: Geveci, Berk (External Contact) <berk.geveci at kitware.com>; Sven Kramer <svenkramer40 at gmail.com>
Cc: ParaView <paraview at paraview.org>
Subject: [EXTERNAL] Re: [Paraview] Comparison of Visit and ParaView development

Hi,

On 15-06-16 16:18, Berk Geveci wrote:
> I believe that the main differentiator between ParaView and other vis 
> tools out there is the broad functionality _and_ the code quality.
> Having the two together is really tough but our community managed this 
> with a heavy emphasis on code review and code testing. I strongly 
> recommend that folks look at the software processes used to develop 
> VTK & ParaView as well as the huge amount of testing (both test 
> quantity and platform coverage) that we do before every single commit 
> in addition to nightly. There is a very good overlap between the 
> CMake, CTest & CDash communities and the VTK/ParaView development 
> communities and there is very good reason behind this.

Slightly off-topic (not fully about ParaView vs VisIt), but I always wondered about the development process of VTK/ParaView with respect to bug reports. There seem to be a huge number of reported bugs for ParaView (and a few for VTK), ranging from crashes to incorrect functionality to feature requests. Over the years I have entered more than two dozen myself, but was always surprised about the lack of response, especially when reporting things that were easily reproducible and/or crasher bugs (e.g. VTK #10528, ParaView #15291, ParaView #15944, ParaView #13802).

Now, I understand that what's not working for me might not be important to others, so, of course, assigning priorty and doing actual fixes for reports is done by the developer community. A second "handicap" in this respect is undoubtedly the fact that KitWare is a business and so has different priorities than a bunch of hackers working mostly in their spare time on their pet project.

But basically anything reported these days immediately gets status "backlog" and I would guesstimate getting a response to a report only about 25% of the time. I report bugs quite often for other open-source projects (and try to enter concise reports with a testcase), but with ParaView/VTK I get the feeling it's not worth the trouble, which is a shame. Actually getting back on topic: the one or two times I reported a bug in VisIt I got a reply and fix quickly!

Furthermore, ParaView seems quite easy to segfault and it happens even with moderately complex pipelines and modest datasets. Parallel volume rendering has been broken for ages (or is it fixed these days? Can't tell, ParaView #13801 did not get any replies). Some examples shown on the wiki cause Python errors (e.g. #15291, #12796). And so on.

So the comment above about code quality making ParaView stand out from other visualization tools is a bit a stretch in my opinion. I would certainly not call ParaView "stable". In fact, in the introductory scivis courses we teach with ParaView we always warn people that crashes are to be expected regularly and even during the course assignments they sometimes happen.

The development process as mentioned by Berk is indeed impressive, but seems mostly focused on preventing regressions in existing functionality. This is a worthy goal in itself, but is only one half of the story when it comes to guaranteeing code quality. The things that aren't working (see bug reports) are maybe not getting the attention they deserve, but are apparently things folks run into when using ParaView, so they signal something real.

After the stuff above I wanted to finish on a less critical note :) I prefer using ParaView over VisIt mostly because of being able to build a pipeline and prefer ParaView's nice single-window GUI over VisIt's a-window-here-a-window-there-a-window-everywhere approach. They are both good and useful tools and are work-horses for scivis tasks. Whenever I get a request from an HPC user which one to use I recommend ParaView, as it is easier to get into for basic scivis work.

Regards,
Paul

-- 

Paul Melis
| Visualization group leader & developer | SURFsara | Science Park 140 | 
| 1098 XG Amsterdam | T 020 800 1312 | paul.melis at surfsara.nl | 
| www.surfsara.nl |
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