Precision vs. Speed ------------------- Debian's beignet 1.0.2+ (unlike the upstream version) defaults to OpenCL-standard-compliant precision, to avoid breaking applications written on other hardware that may assume this. This slows down some of the math functions as they cannot use the (lower-precision) native instructions: most only moderately (eg. ~30% for sin/cos) but ~10-fold for pow and rootn (though not pown or sqrt). Applications that prefer speed to precision may use the native_* functions. The tgamma function is implemented as exp(lgamma) and is hence precision non-compliant for large outputs.