Win7 x64, Vega64, driver 17.10.2
Short description of error
When rendering the same frame of the same scene multiple times with OpenCL with the same instance of Blender, render times vary from 100% to >300%. Restarting Blender and rerendering gives the same time as the first time
Exact steps for others to reproduce the error
- Start latest master of blender with --debug-cycles
- Open the victor scene from official benchmark pack https://download.blender.org/demo/test/cycles_benchmark_20160228.zip , render with GPU (tile size 64x64 for example) many times and note the times without synchronization.
I did it on a small border render part at low resolution to have about 20 tiles of 64x64 with fur and grass. The first render after (re)starting was always 29seconds long, the next ones were random, between 45seconds and 102seconds.
The same test with 2.79 gave 145.6seconds +/-1% on 3 consecutive renders without restart. So the bug appeared after 2.79. Something was changed in allocation or global size calculation maybe?