使用32位和64位加速框架快速进行矩阵乘法 [英] matrix multiplication in swift using Accelerate framework 32 bit vs 64 bit

问题描述

我正在尝试使用Accelerate框架在Swift中进行矩阵乘法。使用了vDSP_mmulD。这在iPhone6、6及更高版本的iPad Air模拟器（所有64位体系结构）中完美运行，但不适用于任何32位体系结构设备。
看起来vDSP_mmulD无法被32位体系结构识别，并且该程序无法构建。显示的错误消息是使用无法解析的标识符'vDSP_mmulD'其他人看到此错误了吗？请让我知道你的想法。我正在使用Xcode 6.1。
谢谢。

解决方案

简单的解决方案：使用 cblas_dgemm 代替（也是Accelerate的一部分）。在所有系统上，它的速度至少与 vDSP_mmulD 一样快，而在某些系统上则要快得多（在iOS 8和Yosemite中， vDSP_mmulD 实际上只是一个 cblas_dgemm 的包装，它实际上应该在这里工作。

我怀疑您的构建是对于32位模拟器失败；在i386上，vDSP_mmulD实际上是mmulD周围的一个宏，而Swift不完全支持C语言宏。

注意：我怀疑您可能正在使用3x3或4x4矩阵，在这种情况下，任何Accelerate例程都不是您真正想要的（它们针对更大的矩阵）；您需要内联矢量序列，例如< simd / matrix.h> 中定义的序列。不幸的是，Swift不支持SIMD向量，因此这不是一种选择。此时最好的选择是简单地写出元素计算，并报告一个错误以要求Swift支持< simd / simd.h> 接口。 / p>

I am trying to do matrix multiplication in Swift using the Accelerate framework. Used the vDSP_mmulD. This worked perfectly in the iPhone6 , 6 plus, iPad Air simulator (all 64 bit architecture) but did not work with any of the 32 bit architecture devices. It sees like vDSP_mmulD is not recognized by the 32 bit architecture and the program does not build. Error message displayed is "use of unresolved identifier 'vDSP_mmulD'" Has anybody else seen this error? Please let me know your thoughts. I am using Xcode 6.1. Thanks.

解决方案

Simple solution: use cblas_dgemm instead (also part of Accelerate). It's at least as fast as vDSP_mmulD on all systems, and much faster on some (in iOS 8 and Yosemite, vDSP_mmulD is actually just a wrapper around cblas_dgemm), and it should actually work here.

I suspect that your build is failing for the 32-bit simulator; on i386, vDSP_mmulD is actually a macro around mmulD, and Swift does not fully support C language macros.

Note: I have a suspicion that you may be working with 3x3 or 4x4 matrices, in which case none of the Accelerate routines are really what you want (they're aimed a larger matrices); you want inline vector sequences like the ones defined in <simd/matrix.h>. Unfortunately, Swift doesn't support SIMD vectors, so that's not an option. Your best bet at this point may be to simply write out the elementwise computation, and report a bug to request that Swift support the <simd/simd.h> interfaces.

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