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NAME |
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Faster - do some things faster |
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|
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SYNOPSIS |
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use Faster; |
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perl -MFaster ... |
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DESCRIPTION |
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This module implements a very simple-minded "JIT" (or actually AIT, |
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ahead of time compiler). It works by more or less translating every |
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function it sees into a C program, compiling it and then replacing the |
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function by the compiled code. |
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|
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As a result, startup times are immense, as every function might lead to |
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a full-blown compilation. |
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|
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The speed improvements are also not great, you can expect 20% or so on |
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average, for code that runs very often. The reason for this is that data |
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handling is mostly being done by the same old code, it just gets called |
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a bit faster. Regexes and string operations won't get faster. Airhtmetic |
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doresn't become any faster. Just the operands and other stuff is put on |
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the stack faster, and the opcodes themselves have a bit less overhead. |
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|
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Faster is in the early stages of development. Due to its design its |
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relatively safe to use (it will either work or simply slowdown the |
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program immensely, but rarely cause bugs). |
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|
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More intelligent algorithms (loop optimisation, type inference) could |
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improve that easily, but requires a much more elaborate presentation and |
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optimiser than what is in place. There are no plans to improve Faster in |
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this way, yet, but it would provide a reasonably good place to start. |
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|
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Usage is very easy, just "use Faster" and every function called from |
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then on will be compiled. |
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|
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Right now, Faster can leave lots of *.c and *.so files in your |
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$FASTER_CACHEDIR (by default $HOME/.perl-faster-cache), and it will even |
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create those temporary files in an insecure manner, so watch out. |
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|
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ENVIRONMENT VARIABLES |
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The following environment variables influence the behaviour of Faster: |
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|
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FASTER_VERBOSE |
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Faster will output more informational messages when set to values |
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higher than 0. Currently, 1 outputs which packages are being |
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compiled, 3 outputs the cache directory and 10 outputs information |
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on which perl function is compiled into which shared object. |
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|
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FASTER_DEBUG |
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Add debugging code when set to values higher than 0. Currently, this |
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adds 1-3 "assert"'s per perl op (FASTER_DEBUG > 1), to ensure that |
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opcode order and C execution order are compatible. |
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|
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FASTER_CACHE |
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Set a persistent cache directory that caches compiled code |
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fragments. The default is "$HOME/.perl-faster-cache" if "HOME" is |
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set and a temporary directory otherwise. |
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|
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This directory will always grow in size, so you might need to erase |
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it from time to time. |
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|
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BUGS/LIMITATIONS |
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Perl will check much less often for asynchronous signals in |
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Faster-compiled code. It tries to check on every function call, loop |
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iteration and every I/O operator, though. |
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|
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The following things will disable Faster. If you manage to enable them |
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at runtime, bad things will happen. Enabling them at startup will be |
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fine, though. |
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|
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enabled tainting |
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enabled debugging |
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|
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Thread-enabled builds of perl will dramatically reduce Faster's |
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performance, but you don't care about speed if you enable threads |
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anyway. |
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|
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These constructs will force the use of the interpreter for the currently |
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executed function as soon as they are being encountered during |
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execution. |
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|
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goto |
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next, redo (but not well-behaved last's) |
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labels, if used |
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eval |
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require |
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any use of formats |
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.., ... (flipflop operators) |
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|
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AUTHOR |
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Marc Lehmann <schmorp@schmorp.de> |
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http://home.schmorp.de/ |
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