{"id":32104,"date":"2021-04-12T17:00:58","date_gmt":"2021-04-12T21:00:58","guid":{"rendered":"https:\/\/mjtsai.com\/blog\/?p=32104"},"modified":"2021-04-15T14:33:31","modified_gmt":"2021-04-15T18:33:31","slug":"high-performance-numeric-programming-with-swift","status":"publish","type":"post","link":"https:\/\/mjtsai.com\/blog\/2021\/04\/12\/high-performance-numeric-programming-with-swift\/","title":{"rendered":"High Performance Numeric Programming With Swift"},"content":{"rendered":"

Jeremy Howard<\/a> (via Frank Illenberger<\/a>):<\/p>\n

I’ve managed to create a couple of libraries that can achieve the same speed as carefully optimized vectorized C code, whilst being concise and easy to use. […] I will include examples mainly from my BaseMath<\/a> library, which provides generic math functions for Float<\/code> and Double<\/code>, and optimized versions for various collections of them.<\/p>

[…]<\/p>

One of the really cool things about Swift is that wrappers like the above have no run-time overhead. As you see, I’ve marked them with the inlinable<\/code> attribute, which tells LLVM that it’s OK to replace calls to this function with the actual function body. This kind of zero-overhead abstraction<\/em> is one of the most important features of C++; it’s really amazing to see it in such a concise and expressive language as Swift.<\/p>

[…]<\/p>

Normally, because Swift has to handle the complexities of COW, it can’t fully optimize a loop like this. But by using a pointer instead, we skip those checks, and Swift can run the code at full speed. Note that due to copy-on-write it’s possible for the array to move if you assign to it, and it can also move if you do things such as resize it; therefore, you should only grab the pointer at the time you need it.<\/p>

[…]<\/p>

I think this is quite remarkable; we’ve been able to create a simple API which is just as fast as the pointer code, but to the class user that complexity is entirely hidden away.<\/p>

[…]<\/p>

I also find Swift’s performance is harder to reason about and optimize than C.<\/p><\/blockquote>\n\n

Previously:<\/p>\n