Matthew, These look like good things for me to use for efficiency in the science collection. Will these these be in the upcoming 4.2.2 release?
I assume that if I use these and introduce a dependency on 4.2.2 or later that I should also bump the version number of the science collection in PLaneT - even if the interface remains the same. Does that make sense? I guess the term 'experiment' here confuses me. Is this something that might go away again? Should I wait until everyone is comfortable with the results? Doug On Sun, Sep 6, 2009 at 12:27 PM, Matthew Flatt <mfl...@cs.utah.edu> wrote: > Version 4.2.1.8 (now in SVN) starts an experiment with > performance-oriented unsafe operations. > > The new `scheme/unsafe/ops' library provides operations such as > `unsafe-vector-ref' and `unsafe-fl+' (for inexact real addition) that > are inlined by the JIT without contract checks. If a call violates the > contract of a function from `scheme/unsafe/ops', arbitrarily bad > things can happen. As long as contracts are satisfied, however, > performance should be a little better than with corresponding safe > operations. > > As part of the experiment, the expansion of `for' with `in-range' and > `in-vector' now uses unsafe operations (in a safe way). For example, > `in-vector' uses `unsafe-vector-ref' as well as a fixnum comparison > for detecting when it has reached the end of a vector; it also uses > unsafe fixnum arithmetic to increment the index as long as the step is > 1 or -1 (in which case no overflow can occur during the > increment). These improvements make a 10-20% difference in a tight > loop over a vector. > > Future possible directions include making the JIT specialize > combinations of inexact operations to avoid boxing intermediate > results. > > The exports of `scheme/unsafe/ops' are protected, so that a code > inspector can prevent access to unsafe operations by untrusted code. > > _________________________________________________ > For list-related administrative tasks: > http://list.cs.brown.edu/mailman/listinfo/plt-dev >
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