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diff --git a/content/zettel/1f4.md b/content/zettel/1f4.md new file mode 100644 index 0000000..1f1184f --- /dev/null +++ b/content/zettel/1f4.md @@ -0,0 +1,28 @@ ++++ +title = "Complex optimisation effects" +author = "Yann Herklotz" +tags = [] +categories = [] +backlinks = ["1f3"] +forwardlinks = ["1f4a"] +zettelid = "1f4" ++++ + +Finally, the last flakiness property that HLS tools have is that they +apply many optimisations, which may or may not have linear effects on +the performance and area of the result. + +> Because of Amdahl's law arguments, most optimizations don't have a +> linear effect. They appear to have a linear effect sometimes, but +> eventually hit some diminishing returns. Some other effects are really +> discontinuous, for instance, unrolling accumulation loops may not +> change critical recurrences. — Stephen Neuendorffer ([email]) + +It's is nearly impossible to predict what a series of optimisations will +do to the performance. The user will implicitly try to predict the +performance with a simplified model as reference, and as the HLS tool +has to take everything into account, and will therefore sometimes not be +able to optimise the loop as the user would want it to be, leading to +discontinuous optimisations. + + [email]: notmuch:id:BYAPR02MB3910A2FA9F954031FC11A232A8479@BYAPR02MB3910.namprd02.prod.outlook.com |