That was a nasty one, Debug build would never have any issue (even tried
with 64 threads!), but Release build would deadlock nearly immediately,
even with only 2 threads!
What happened here (I think) is that gcc optimizer would generate a
specific path endlessly looping when initial value of virtual_lock was
FLT_MAX, by-passing re-assignment from v_no[0] and the atomic cas
completely. Which would have been correct, should v_no[0] not have been
shared (and modified) by multiple threads. ;)
Idea of that (broken) for loop was to avoid completely calling the
atomic cas as long as v_no[0] was locked by some other thread, but...
Guess the avoided/missing memory barrier was the root of the issue here.
Lesson of the evening: Remember kids, do not trust your compiler to
understand all possible threading-related side effects, and be explicit
rather than elegant when using atomic ops!
Side-effect lesson: do check both release and debug builds when messing
with said atomic ops...
Using atomic cas correctly is really hairy... ;)
In this case, the returned value from cas needs to validate *two*
conditions, it must not be FLT_MAX (which is our 'locked' value and
would mean another thread has already locked it), but it also must be
equal to previously stored value...
This means we need two steps per loop here, hence using a 'for' loop
instead of a 'while' one now.
Note that collisions are (as expected) very rare, less than 1 for 10k
typically, so did not catch the issue initially (also because I was
mostly working with release build to check on performances...).
`BM_mesh_normals_update` was converted from OMP to new parallel iterator code,
basic test with heavily subdivided cube (24.5k faces) gives:
- old OMP code: average 10ms per run.
- new BLI_task code: average 6ms per run.
So new code seems to be easily 40% quicker, in addition to getting rid of OMP. ;)
Reviewers: sergey, campbellbarton
Differential Revision: https://developer.blender.org/D2930
It merely uses the new thread-safe iterators system of mempool, quite
straight forward.
Note that to avoid possible confusion with two void pointers as
parameters of the callback, a dummy opaque struct pointer is used
instead for the second parameter (pointer generated by iteration over
mempool), callback functions must explicitely convert it to expected
real type.
Also added a basic gtest for this new feature.
This will allow threaded tasks to 'consume' all mempool items in
parallel tasks, each one working on a whole chunk at once (to reduce
concurrency managing overhead).
Adapted from http://www.pixelbeat.org/programming/gcc/static_assert.html.
Note that this macro just discards error message, so error when building
is much less nice than with gcc's _Static_assert... But error log will
point to right place in code, so should still be OK.
Pixel size was not initial early enough. For first time this was not a problem
because the bevel amount starts at 0 then, and after the mouse moves the pixel
size is initialized. For the second time the bevel amount starts at a non-zero
value, and it failed then.
These and other non-RGB passes should always be stored as full float, the
precision loss is too unpredictable.
Related to T53381, but that one is about file output nodes where we don't
know the type of data being saved currently.
This reverts commit d749320e3b.
It's possible the container struct is larger,
we could do sizeof checks that falls back to memmove
but rather avoid complicating things.
Just removing it, such cases are not bottlenecks and not worth the
complication of doing real threading with own BLI_task.
Other (remaining) usages may be relevant, need case-by-case check.
This was expected behavior for over-exposured lamps when the mode was originally
created for Tears of Steel. Turns out, there could be really bad green screen in
real production which will only have green (or rather screen) channel over
exposured.
Tweaked condition now so we use least bright channel to see if the area has
proper exposure or not.
Seems to work fine in tests, but further tweaks are possible.
Regression from rB823bcf1689a3 (VPaint 2017 GSoC, this is not in 2.79 release).
Also cleanup, using fake-array-ification to access struct members is
generally not a great idea, but when we already have a totally confusing
broken struct layout, this is pure evil, as demonstrated here!
Found while investigating T53341.
- initialize the cube-size from the bounding box when it's not set.
- no longer wrap faces to keep in 0-1 bounds,
other projection methods don't do this and calculating the scale
prevents the UV's from being too far outside the view.
Was using cursor position from within menu,
clicking on the same position for every selected item (toggling).
Now operate on each selected outliner element, without toggling.
