I got myself a snazzy new AMD R9 390 and decided to play with FLACCL. CPU is a quad-core i5-3570 (non-K, stock speeds) and the filesystem resides in an SSD drive. The --cpu-threads switch provides a huge speedup (more than doubles encoding speed) set for 2 threads. 3 and 4 threads actually seem to slow down encoding slightly compared to using 2 threads. GPU drivers are latest Crimson non-WHQL.
C:\output>CUETools.FLACCL.cmd.exe Image.wav
CUETools FLACCL 2.1.6, Copyright (C) 2010-2013 Grigory Chudov.
This is free software under the GNU GPLv3+ license; There is NO WARRANTY, to
the extent permitted by law. <http://www.gnu.org/licenses/> for details.
Filename : Image.wav
File Info : 44100kHz; 2 channel; 16 bit; 02:29:57.3500000
Device : Hawaii, Platform: "AMD Accelerated Parallel Processing", Version: Op
enCL 2.0 AMD-APP (2004.6), Driver: 2004.6 (VM)
Run 1 Results : 833.97x; 1118786860 bytes in 00:00:10.7886170 seconds;
Run 2 Results : 834.12x; 1118786860 bytes in 00:00:10.7866170 seconds;
Run 3 Results : 833.66x; 1118786860 bytes in 00:00:10.7926173 seconds;
C:\output>CUETools.FLACCL.cmd.exe --cpu-threads 2 Image.wav
Run 1 Results : 1737.85x; 1118786860 bytes in 00:00:05.1772961 seconds;
Run 2 Results : 1734.16x; 1118786860 bytes in 00:00:05.1882968 seconds;
Run 3 Results : 1730.83x; 1118786860 bytes in 00:00:05.1982973 seconds;
C:\output>CUETools.FLACCL.cmd.exe --cpu-threads 3 Image.wav
Run 1 Results : 1725.18x; 1118786860 bytes in 00:00:05.2152983 seconds;
Run 2 Results : 1726.51x; 1118786860 bytes in 00:00:05.2112981 seconds;
Run 3 Results : 1724.52x; 1118786860 bytes in 00:00:05.2172984 seconds;
C:\output>CUETools.FLACCL.cmd.exe --cpu-threads 4 Image.wav
Run 1 Results : 1724.85x; 1118786860 bytes in 00:00:05.2162984 seconds;
Run 2 Results : 1721.55x; 1118786860 bytes in 00:00:05.2262990 seconds;
Run 3 Results : 1723.86x; 1118786860 bytes in 00:00:05.2192985 seconds;
Compared to Flake
C:\output>CUETools.Flake.exe Image.wav
CUETools.Flake, Copyright (C) 2009-2014 Grigory Chudov.
Initially based on Flake encoder by Justin Ruggles.
This is free software under the GNU GPLv3+ license; There is NO WARRANTY, to
the extent permitted by law. <http://www.gnu.org/licenses/> for details.
Filename : Image.wav
File Info : 44100kHz; 2 channel; 16 bit; 02:29:57.3500000
Run 1 Results : 231.13x; 1118353797 bytes in 00:00:38.9282265 seconds;
Run 2 Results : 229.93x; 1118353797 bytes in 00:00:39.1302381 seconds;
Run 3 Results : 230.75x; 1118353797 bytes in 00:00:38.9912302 seconds;