Adaptive optimization is a technique in
computer science
Computer science is the study of computation, information, and automation. Computer science spans Theoretical computer science, theoretical disciplines (such as algorithms, theory of computation, and information theory) to Applied science, ...
that performs
dynamic recompilation
In computer science, dynamic recompilation is a feature of some emulators and virtual machines, where the system may recompile some part of a program during execution. By compiling during execution, the system can tailor the generated code to ...
of portions of a
program based on the current execution profile. With a simple implementation, an adaptive optimizer may simply make a trade-off between
just-in-time compilation
In computing, just-in-time (JIT) compilation (also dynamic translation or run-time compilations) is compilation (of computer code) during execution of a program (at run time) rather than before execution. This may consist of source code transl ...
and
interpreting instructions. At another level, adaptive optimization may take advantage of local data conditions to optimize away branches and to use
inline expansion
In computing, inline expansion, or inlining, is a manual or compiler optimization that replaces a function call site with the body of the called function. Inline expansion is similar to macro expansion, but occurs during compiling, without cha ...
to decrease the cost of procedure calls.
Consider a hypothetical banking application that handles transactions one after another. These transactions may be checks, deposits, and a large number of more obscure transactions. When the program executes, the actual data may consist of clearing tens of thousands of checks without processing a single deposit and without processing a single check with a fraudulent account number. An adaptive optimizer would compile assembly code to optimize for this common case. If the system then started processing tens of thousands of deposits instead, the adaptive optimizer would recompile the assembly code to optimize the new common case. This optimization may include inlining code.
Examples of adaptive optimization include
HotSpot and HP's
Dynamo system.
HP's Dynamo
/ref>
In some systems, notably the Java Virtual Machine
A Java virtual machine (JVM) is a virtual machine that enables a computer to run Java programs as well as programs written in other languages that are also compiled to Java bytecode. The JVM is detailed by a specification that formally descr ...
, execution over a range of bytecode instructions can be provably reversed. This allows an adaptive optimizer to make risky assumptions about the code. In the above example, the optimizer may assume all transactions are checks and all account numbers are valid. When these assumptions prove incorrect, the adaptive optimizer can 'unwind' to a valid state and then interpret the byte code instructions correctly.
See also
* Profile-guided optimization
* Hot spot (computer programming)
References
{{Reflist
External links
CiteSeer for "Adaptive Optimization in the Jalapeño JVM (2000)"
by Matthew Arnold, Stephen Fink, David Grove, Michael Hind, Peter F. Sweeney. Contains links to the full paper in various formats.
Compiler optimizations