Did you know that hand-optimized assembler is slower then allegedly “slow” languages, say, Lisp or JavaScript? It’s true, if you wait long enough.<\/p>\n
Imagine you have found some old hand-tuned Lisp code, and a hand-tuned I expect that ultimately JavaScript will outperform contemporary SSE code, because hardware inevitably becomes obsolete over time.<\/p>\n When assembly code becomes obsolete, you are stuck with two slow options. Use obsolete hardware to execute the code, or emulate your obsolete hardware on a new computer (since computers keep getting faster, emulation will become the fastest choice). Meanwhile the high-level code will still be executable, and<\/em> able to take advantage of all subsequent hardware improvements.<\/p>\n Some x86 instructions are already obsolete; by which I mean they give worse performance then more common instructions.<\/p>\n Assembly\/Compiler Coding Rule 31. (ML impact, M generality) Avoid using complex instructions (for example, enter, leave, or loop) that have more than four \u00b5ops and require multiple cycles to decode. Use sequences of simple instructions instead. <\/p><\/blockquote>\n — Intel\u00ae64 and IA-32 Architectures Optimization Reference Manual<\/a><\/p>\n You could say that this is all academic, because in half a century the code you wrote today will be irrelevant, and I would agree. PDP-1 vs Lisp was hypothetical hyperbole, show that the benefits of low-level optimization decrease the longer the code is in use<\/strong>, because the advantages compared to high-level code decrease over time. <\/p>\n What really drove this home for me was Apple’s switch from PPC to x86<\/a>. Suddenly all the AltiVec<\/a> code I’d ever written was obsolete. If someone bought a new Mac, my AltiVec code would be emulated, and slower then unchanged (but recompiled) C code! I could have reused existing AltiVec code to create SSE code<\/a>, but then I would be stuck doing optimization work every time a sufficiently new computer came out<\/em>.<\/p>\n Algorithmic-level optimization holds it’s value over time; low-level optimization does not. However, software is such a rapidly-changing environment that a short-term investment can still make a hell of a lot of sense.<\/p>\n","protected":false},"excerpt":{"rendered":" Did you know that hand-optimized assembler is slower then allegedly “slow” languages, say, Lisp or JavaScript? It’s true, if you wait long enough. Imagine you have found some old hand-tuned Lisp code, and a hand-tuned PDP-1 assembly language version. If you executed both programs today, using a modern Lisp interpreter and a modern PDP-1 emulator, […]<\/p>\n","protected":false},"author":1,"featured_media":0,"comment_status":"open","ping_status":"open","sticky":false,"template":"","format":"standard","meta":{"footnotes":""},"categories":[3,4,10],"tags":[],"class_list":["post-8","post","type-post","status-publish","format-standard","hentry","category-macosx","category-programming","category-tips"],"_links":{"self":[{"href":"https:\/\/vgable.com\/blog\/wp-json\/wp\/v2\/posts\/8","targetHints":{"allow":["GET"]}}],"collection":[{"href":"https:\/\/vgable.com\/blog\/wp-json\/wp\/v2\/posts"}],"about":[{"href":"https:\/\/vgable.com\/blog\/wp-json\/wp\/v2\/types\/post"}],"author":[{"embeddable":true,"href":"https:\/\/vgable.com\/blog\/wp-json\/wp\/v2\/users\/1"}],"replies":[{"embeddable":true,"href":"https:\/\/vgable.com\/blog\/wp-json\/wp\/v2\/comments?post=8"}],"version-history":[{"count":0,"href":"https:\/\/vgable.com\/blog\/wp-json\/wp\/v2\/posts\/8\/revisions"}],"wp:attachment":[{"href":"https:\/\/vgable.com\/blog\/wp-json\/wp\/v2\/media?parent=8"}],"wp:term":[{"taxonomy":"category","embeddable":true,"href":"https:\/\/vgable.com\/blog\/wp-json\/wp\/v2\/categories?post=8"},{"taxonomy":"post_tag","embeddable":true,"href":"https:\/\/vgable.com\/blog\/wp-json\/wp\/v2\/tags?post=8"}],"curies":[{"name":"wp","href":"https:\/\/api.w.org\/{rel}","templated":true}]}}