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copied!<p>Very loosely speaking, it is not entirely unreasonable to say that a Haswell core has about 16 CUDA cores, but you definitely don't want to take that comparison too far. You may want to be cautious about making that statement directly in a presentation, but I've found it to be useful to think of a CUDA core as being somewhat related to a scalar FP unit.</p> <p>It may help if I explain why Haswell can perform 32 single-precision operations per cycle.</p> <ul> <li><p>8 single-precision operations execute in each AVX/AVX2 instruction. When writing code that will run on a Haswell CPU, you can use AVX and AVX2 instructions which operate on 256-bit vectors. These 256-bit vectors can represent 8 single-precision FP numbers, 8 integers (32-bit) or 4 double-precision FP numbers.</p></li> <li><p>2 AVX/AVX2 instructions can execute in each core per cycle, although there are some restrictions on which instructions can be paired up.</p></li> <li><p>A fused multiply add (FMA) instruction technically performs 2 single-precision operations. FMA instructions perform "fused" operations such as A = A * B + C, so there are arguably two operations per scalar operand: a multiplication and an addition.</p></li> </ul> <p>This article explains the above points in more detail: <a href="http://www.realworldtech.com/haswell-cpu/4/" rel="noreferrer">http://www.realworldtech.com/haswell-cpu/4/</a></p> <p>In the total accounting, a Haswell core can perform 8 * 2 * 2 single-precision operations per cycle. Since CUDA cores support FMA operations as well, you cannot count that factor of 2 when comparing CUDA cores to Haswell cores.</p> <p>A Kepler CUDA core has one single-precision floating-point unit, so it can perform one floating-point operation per cycle: <a href="http://www.nvidia.com/content/PDF/kepler/NVIDIA-Kepler-GK110-Architecture-Whitepaper.pdf" rel="noreferrer">http://www.nvidia.com/content/PDF/kepler/NVIDIA-Kepler-GK110-Architecture-Whitepaper.pdf</a>, <a href="http://www.realworldtech.com/kepler-brief/" rel="noreferrer">http://www.realworldtech.com/kepler-brief/</a></p> <p>If I was putting together slides on this, I would have one section explaining how many FP operations Haswell can do per cycle: the three points above, plus you have multiple cores and possibly multiple processors. And, I'd have another section explaining how many FP operations a Kepler GPU can do per cycle: 192 per SMX, and you have multiple SMX units on the GPU.</p> <p>PS.: I may be stating the obvious, but just to avoid confusion: the Haswell architecture also includes an integrated GPU, which has an altogether different architecture from the Haswell CPU.</p>

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