OpenCL, AES, Luxmark
We wanted to check the relative levels of performance of various OpenCL applications. When introducing the Radeon HD 7970s, AMD talked about a version of WinZip (16.5!) that supposedly used OpenCL to accelerate AES encryption. This version still isn’t available.
We turned to three OpenCL tests. Firstly an AES encryption test from AMD’s SDK. Secondly LuxMark, a benchmark from LuxRender that uses OpenCL.
Update: 23/01Thirdly DxO Optics Pro in version 7.1, the RAW export functionality of which we tested, as it may also use OpenCL.
DxO Optics Pro 7
We have added the DxO Optics Pro 7.1 photo processing software to our protocol. We used the RAW to JPEG development feature on 50 files, a feature that has been in OpenCL since version 7 of the software. We carried out two series of tests, first authorising the conversion of one and then two files simultaneously. Beyond this, processor performance tends to limit the performance of the graphics card. For info, we also added the conversion time obtained with the processor alone.
While there is a slight impact in different modes, in practice the differences remain slim. Note that the x16 modes are systematically faster – at equal bandwidth – than the others.
AMD supplies the source code
for a piece of AES encryption software with its SDK APP. For this test we used a 190 MB photo, transferred to the GPU where it is transformed and then sent back to the CPU before being written to the drive. The test measures the transfer and processing times.
The differences are extremely small here though PCI Express 3.0 x16 mode does have a slight advantage (in the order of a hundredth of a second). Having more bandwidth doesn’t make much of a difference in practice here.
We used the Windows 64-bit version of LuxMark in 100% OpenCL mode. The test supports CrossFire.
Here again, the gains are extremely slight, with 3.0 x16 just a hairsbreadth ahead of 2.0 x16. The additional bandwidth contributes very little. Note that while PCI Express 3.0 x4 is the most efficient of the equivalent modes without CrossFire, with CrossFire performance drops off and it no longer is. PCI Express 3.0 x8 is very slightly up on 2.0 x16 in both cases.
Let’s now move on to games and see if we can obtain bigger performance differences!