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"The API itself is not the reason for its performance" It eliminates many performance mistakes by making it so that when you do something dumb it's generally i

by geokon 4y ago

"The API itself is not the reason for its performance" It eliminates many performance mistakes by making it so that when you do something dumb it's generally immediately apparent. This mostly boils down to nonsensical/slow operations being usually impossible and any memory copying being explicit. I can only tell you my own experience. Going through the steps of transforming a few "textbook algorithms" into BLAS made me think about the problems much more clearly and in a way I would have missed using a higher abstraction. All the examples you give (Matlab, eigen, armadillo, Julia) allow you to really easily write really bad code (blas under the hood is kinda irrelevant). But you're totally right that they're useful. If you want to call out to code that does an SVD or something simple that exists in a library then they're generally just fine and you can't mess it up too much. I use BLAS with a repl from Clojure (thanks to neanderthal) so it's very painless. Sounds like you're using it in a compile/run loop from C/C++ which sounds like very much not fun.

sfpotter 4y ago
Here's BLIS's object API: https://github.com/flame/blis/blob/master/docs/BLISObjectAPI.md#level-2-operations https://github.com/flame/blis/blob/master/docs/BLISObjectAPI... Searching "object" in BLIS's README (https://github.com/flame/blis https://github.com/flame/blis) to see what they think of it: "Objects are relatively lightweight structs and passed by address, which helps tame function calling overhead." "This is API abstracts away properties of vectors and matrices within obj_t structs that can be queried with accessor functions. Many developers and experts prefer this API over the typed API." In my opinion, this API is a strict improvement over BLAS. I do not think there is any reason to prefer the old BLAS-style API over an improvement like this. Regarding your own experience, it's great that using BLAS proved to be a valuable learning experience for you. But your argument that the BLAS API is somehow uniquely helpful in terms of learning how to program numerical algorithms efficiently, or that it will help you avoid performance problems, is not true. It is possible to replace the BLAS API with a more modern and intuitive API with the same benefits. To be clear, the benefits here are direct memory management and control of striding and matrix layout, which create opportunities for optimization. There is nothing unique about BLAS in this regard---it's possible to learn these lessons using any of the other listed options if you're paying attention and being systematic.

by geokon 4y ago

sfpotter 4y ago

Here's BLIS's object API: https://github.com/flame/blis/blob/master/docs/BLISObjectAPI.md#level-2-operations https://github.com/flame/blis/blob/master/docs/BLISObjectAPI... Searching "object" in BLIS's README (https://github.com/flame/blis https://github.com/flame/blis) to see what they think of it: "Objects are relatively lightweight structs and passed by address, which helps tame function calling overhead." "This is API abstracts away properties of vectors and matrices within obj_t structs that can be queried with accessor functions. Many developers and experts prefer this API over the typed API." In my opinion, this API is a strict improvement over BLAS. I do not think there is any reason to prefer the old BLAS-style API over an improvement like this. Regarding your own experience, it's great that using BLAS proved to be a valuable learning experience for you. But your argument that the BLAS API is somehow uniquely helpful in terms of learning how to program numerical algorithms efficiently, or that it will help you avoid performance problems, is not true. It is possible to replace the BLAS API with a more modern and intuitive API with the same benefits. To be clear, the benefits here are direct memory management and control of striding and matrix layout, which create opportunities for optimization. There is nothing unique about BLAS in this regard---it's possible to learn these lessons using any of the other listed options if you're paying attention and being systematic.