[Bf-cycles] CMJ causing an infinite loop
Brecht Van Lommel
brechtvanlommel at pandora.be
Mon Apr 14 13:52:45 CEST 2014
I haven't seen this before, can you figure out the values s, N and p
that are causing this problem? Or attach a .blend file with the
problem? I can't see it from your backtrace. As long as 0 <= s < N it
should not hang, but this permutation function is of course pretty
tricky so it's difficult to spot the bug from just the code.
For adaptive sampling, Sobol is supposed to be good at this I thought.
But I guess you look at the even samples because that's easy to do
memory efficient compared to looking at the first half of the samples,
and makes it possible to stop at any time rather than each time the
number of samples doubles. Perhaps you can probabilistically use
either the even or odd sample, with the random number based on a hash
of the sample number and pixel xy? CMJ should be fixed of course, this
is just an idea.
On Sat, Apr 12, 2014 at 6:36 PM, Lukas Stockner
<lukas.stockner at freenet.de> wrote:
> Hi,
> while working on adaptive stopping I noticed that sometimes tiles just
> freeze when using CMJ sampling. They are marked as active, but don't
> return from the kernel.
> After running in GDB, stopping and printing out the thread states, it
> seems that they enter an infinite loop in cmj_permute(). The entire
> thread states are below, 5 rendering threads work fine, 3 are hanging.
> The "kernel_write_pass_data" is one of my changes, but it's completely
> unrelated to sampling and works correctly with Sobol.
> Is this a known problem? I can't imagine that my changes cause it to
> break since I changed nothing related to CMJ. Sadly, I can't just use
> Sobol instead since it gives correlation problems (the stopping works on
> the difference between even passes and all passes, and with Sobol they
> don't converge to the same result. A solution would be to decide whether
> to add a sample to the "even buffer" with a new RNG sample).
>
> Lukas Stockner
>
>
>
>
>
>
> (gdb) info threads
> Id Target Id Frame
> 44 Thread 0x7fffb1e21700 (LWP 25975) "blender" cmj_permute
> (p=1102306825, l=44721, i=1576503139) at
> /home/lukas/BlenderSrc/blender/intern/cycles/kernel/kernel_jitter.h:107
> 43 Thread 0x7fffb2eb6700 (LWP 25974) "blender" 0x00007fffee61fb42
> in ?? () from /usr/lib/x86_64-linux-gnu/libgomp.so.1
> 42 Thread 0x7fffb39bd700 (LWP 25973) "blender" 0x00007fffee61fb42
> in ?? () from /usr/lib/x86_64-linux-gnu/libgomp.so.1
> 41 Thread 0x7fffb44c4700 (LWP 25972) "blender" 0x00007fffee61fb42
> in ?? () from /usr/lib/x86_64-linux-gnu/libgomp.so.1
> 40 Thread 0x7fffb4fcb700 (LWP 25971) "blender" 0x00007fffee61fb42
> in ?? () from /usr/lib/x86_64-linux-gnu/libgomp.so.1
> 39 Thread 0x7fffb5ad2700 (LWP 25970) "blender" 0x00007fffee61fb42
> in ?? () from /usr/lib/x86_64-linux-gnu/libgomp.so.1
> 38 Thread 0x7fffb65d9700 (LWP 25969) "blender" 0x00007fffee61fb42
> in ?? () from /usr/lib/x86_64-linux-gnu/libgomp.so.1
> 37 Thread 0x7fffb70e0700 (LWP 25968) "blender" 0x00007fffee61fb42
> in ?? () from /usr/lib/x86_64-linux-gnu/libgomp.so.1
> 36 Thread 0x7fffbd3cf700 (LWP 25967) "blender" 0x0000000003637a1d
> in kernel_write_pass_data (L=..., evenSample=true, writeVarData=true,
> writeConstData=false, weight=1, sample=258,
> buffer=0x60a2028558d0, pd=0x7fffbd3c1d20, kg=0x7fffbd3c2610) at
> /home/lukas/BlenderSrc/blender/intern/cycles/kernel/kernel_passes.h:148
> 35 Thread 0x7fffbded6700 (LWP 25966) "blender" cmj_permute
> (p=2243010963, l=44721, i=3758030672) at
> /home/lukas/BlenderSrc/blender/intern/cycles/kernel/kernel_jitter.h:104
> 34 Thread 0x7fffbe9dd700 (LWP 25965) "blender" 0x00007ffff2ef9c84
> in pthread_cond_wait@@GLIBC_2.3.2 () from
> /lib/x86_64-linux-gnu/libpthread.so.0
> 33 Thread 0x7fffbf4e4700 (LWP 25964) "blender" 0x00000000034ee00f
> in cmj_permute (p=3837528855, l=44721, i=3522537535) at
> /home/lukas/BlenderSrc/blender/intern/cycles/kernel/kernel_jitter.h:102
> 32 Thread 0x7fffbffeb700 (LWP 25963) "blender" 0x00000000034f24f2
> in ccl::bvh_intersect_instancing (kg=kg at entry=0x7fffbffde610,
> ray=ray at entry=0x7fffbffccd50, isect=isect at entry=0x7fffbffcc8d0,
> visibility=visibility at entry=256) at
> /home/lukas/BlenderSrc/blender/intern/cycles/kernel/kernel_bvh_traversal.h:194
> 31 Thread 0x7fffc0af2700 (LWP 25962) "blender" 0x00000000034ee00f
> in cmj_permute (p=2537997320, l=44721, i=1494394943) at
> /home/lukas/BlenderSrc/blender/intern/cycles/kernel/kernel_jitter.h:102
> 30 Thread 0x7fffc15f9700 (LWP 25961) "blender" 0x0000000003532c5d
> in fetch (this=0xc110, index=<optimized out>) at
> /home/lukas/BlenderSrc/blender/intern/cycles/kernel/kernel_compat_cpu.h:43
> 29 Thread 0x7fffc1dfa700 (LWP 25960) "blender" cmj_permute
> (p=3687792016, l=44721, i=4285244509) at
> /home/lukas/BlenderSrc/blender/intern/cycles/kernel/kernel_jitter.h:98
> 28 Thread 0x7fffd0f27700 (LWP 25958) "blender" 0x00007ffff2ef71f8
> in pthread_join () from /lib/x86_64-linux-gnu/libpthread.so.0
> 27 Thread 0x7fffc8e63700 (LWP 25957) "blender" 0x00007fffee61fb42
> in ?? () from /usr/lib/x86_64-linux-gnu/libgomp.so.1
> 26 Thread 0x7fffc996a700 (LWP 25956) "blender" 0x00007fffee61fb42
> in ?? () from /usr/lib/x86_64-linux-gnu/libgomp.so.1
> 25 Thread 0x7fffca471700 (LWP 25955) "blender" 0x00007fffee61fb42
> in ?? () from /usr/lib/x86_64-linux-gnu/libgomp.so.1
> 24 Thread 0x7fffcaf78700 (LWP 25954) "blender" 0x00007fffee61fb42
> in ?? () from /usr/lib/x86_64-linux-gnu/libgomp.so.1
> 23 Thread 0x7fffcba7f700 (LWP 25953) "blender" 0x00007fffee61fb42
> in ?? () from /usr/lib/x86_64-linux-gnu/libgomp.so.1
> 22 Thread 0x7fffcc586700 (LWP 25952) "blender" 0x00007fffee61fb42
> in ?? () from /usr/lib/x86_64-linux-gnu/libgomp.so.1
> 21 Thread 0x7fffcd08d700 (LWP 25951) "blender" 0x00007fffee61fb42
> in ?? () from /usr/lib/x86_64-linux-gnu/libgomp.so.1
> 20 Thread 0x7fffd256e700 (LWP 25950) "blender" 0x00007ffff2ef9c84
> in pthread_cond_wait@@GLIBC_2.3.2 () from
> /lib/x86_64-linux-gnu/libpthread.so.0
> 19 Thread 0x7fffd3075700 (LWP 25949) "blender" 0x00007ffff2ef9c84
> in pthread_cond_wait@@GLIBC_2.3.2 () from
> /lib/x86_64-linux-gnu/libpthread.so.0
> 18 Thread 0x7fffd3b7c700 (LWP 25948) "blender" 0x00007ffff2ef9c84
> in pthread_cond_wait@@GLIBC_2.3.2 () from
> /lib/x86_64-linux-gnu/libpthread.so.0
> 17 Thread 0x7fffd4683700 (LWP 25947) "blender" 0x00007ffff2ef9c84
> in pthread_cond_wait@@GLIBC_2.3.2 () from
> /lib/x86_64-linux-gnu/libpthread.so.0
> 16 Thread 0x7fffd518a700 (LWP 25946) "blender" 0x00007ffff2ef9c84
> in pthread_cond_wait@@GLIBC_2.3.2 () from
> /lib/x86_64-linux-gnu/libpthread.so.0
> 15 Thread 0x7fffd5c91700 (LWP 25945) "blender" 0x00007ffff2ef9c84
> in pthread_cond_wait@@GLIBC_2.3.2 () from
> /lib/x86_64-linux-gnu/libpthread.so.0
> 14 Thread 0x7fffd6798700 (LWP 25944) "blender" 0x00007ffff2ef9c84
> in pthread_cond_wait@@GLIBC_2.3.2 () from
> /lib/x86_64-linux-gnu/libpthread.so.0
> 12 Thread 0x7fffdcc00700 (LWP 25941) "blender" 0x00007ffff2efd41d
> in nanosleep () from /lib/x86_64-linux-gnu/libpthread.so.0
> 11 Thread 0x7fffe1a0e700 (LWP 25940) "threaded-ml"
> 0x00007fffeef1af7d in poll () from /lib/x86_64-linux-gnu/libc.so.6
> 9 Thread 0x7fffe253c700 (LWP 25938) "blender" 0x00007ffff2efbf60
> in sem_wait () from /lib/x86_64-linux-gnu/libpthread.so.0
> 8 Thread 0x7fffe3043700 (LWP 25937) "blender" 0x00007ffff2efbf60
> in sem_wait () from /lib/x86_64-linux-gnu/libpthread.so.0
> 7 Thread 0x7fffe3b4a700 (LWP 25936) "blender" 0x00007ffff2efbf60
> in sem_wait () from /lib/x86_64-linux-gnu/libpthread.so.0
> 6 Thread 0x7fffe4651700 (LWP 25935) "blender" 0x00007ffff2efbf60
> in sem_wait () from /lib/x86_64-linux-gnu/libpthread.so.0
> 5 Thread 0x7fffe5158700 (LWP 25934) "blender" 0x00007ffff2efbf60
> in sem_wait () from /lib/x86_64-linux-gnu/libpthread.so.0
> 4 Thread 0x7fffe5c5f700 (LWP 25933) "blender" 0x00007ffff2efbf60
> in sem_wait () from /lib/x86_64-linux-gnu/libpthread.so.0
> 3 Thread 0x7fffe6766700 (LWP 25932) "blender" 0x00007ffff2efbf60
> in sem_wait () from /lib/x86_64-linux-gnu/libpthread.so.0
> 2 Thread 0x7fffe726d700 (LWP 25931) "blender" 0x00007ffff2efbf60
> in sem_wait () from /lib/x86_64-linux-gnu/libpthread.so.0
> * 1 Thread 0x7ffff7fb87c0 (LWP 25927) "blender" 0x00007fffdb6bc36c in
> ?? () from /usr/lib/x86_64-linux-gnu/dri/nouveau_dri.so
>
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