thor220 :
The author of this article didn't do his research. Vulkan isn't a competitor to mantle because Vulkan's new features are all based off Mantle. It would be like saying Vulkan is a competitor to previous versions of OpenGL.
What this does tell me is that Nvidia could have support Mantle at any time they wanted to but just didn't because that would mean giving in to AMD. Now that mantle has merged with Vulkan, Nvidia is more than happy to include it. I guess they don't really have a choice though seeing as they were already caught being behind on DX 12. I expect AMD to outperform Nvidia on Vulkan.
Nvidia didn't have support for Mantle because it was proprietary to AMD GPUs. It was open in the sense that any game developer could use it, but not in the sense that Nvidia and Intel could implement support for it.
And it is still accurate to say that Mantle and Vulkan are competitors. AMD has been quite clear that it wanted to help restart the development of gaming APIs, which had essentially stalled. AMD helped with the development of Vulkan, but that doesn't make Mantle and Vulkan the same. Vulkan isn't "Mantle 2.0". Games that were developed and supported Mantle don't all of a sudden have support for Vulkan. They are still clearly different and recognizable APIs that compete against each other.