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The OpenCL standard allows targeting a large variety of CPU,
GPU and accelerator architectures using a single unified programming inter-
face and language. While the standard guarantees portability of functionality
for complying applications and platforms, performance portability on such a
diverse set of hardware is limited. Devices may vary significantly in memory
architecture as well as type, number and complexity of computational units.
uCLbench is designed to characterize and compare the OpenCL performance 
of existing and future devices and software platforms.

Benchmark Design

The primary purpose of the suite is to characterize and compare the low-level 
performance of OpenCL devices and implementations. As such, we did not employ 
device-specific workarounds to ameliorate problems affecting performance on some 
particular device, since the same behavior would be encountered by actual programs. 

There are three main implementation challenges for uCLbench:
1. Ensure accuracy. The benchmarks need to actually measure the intended
quantity on all devices tested, and it must be possible to verify the computations
2. Minimize overheads. Overheads are always a concern in microbenchmarks,
but with the variety of devices available to OpenCL they can be hard to avoid.
E.g. a simple loop that is negligible in its performance impact on a general
purpose CPU can easily dominate completion time on a GPU.
3. Prevent compiler optimization. Since kernel code is compiled at runtime
using the compiler provided by the OpenCL implementation, we have no control
over the generated code. Thus it is imperative to design the benchmarks in a
way that does not allow the compiler to perform unintended optimizations. Such
optimizations could result in the removal of operations that should be measured.


See the INSTALL file for installation instructions.


uCLbench is distributed under the GPL3, for more information see COPYING.

Authors and Contact Information



Set of OpenCL microbenchmarks




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