joepie91
/
pegjs
1
0
Fork 0
Code Issues Pull Requests Releases Wiki Activity
You cannot select more than 25 topics Topics must start with a letter or number, can include dashes ('-') and can be up to 35 characters long.
redux
master
Branches Tags
${ item.name }
Create tag ${ searchTerm }
Create branch ${ searchTerm }
from '0a1cea5f12'
${ noResults }
pegjs/test
History
David Majda d123cf0eda Rewrite variable handling in generated parsers 
Before this commit, variables for saving match results and parse
positions in generated parsers were not used efficiently. Each rule
basically used its own variable(s) for storing the data, with names
generated sequentially during code emitting. There was no reuse of
variables and a lot of unnecessary assignments between them.

It is easy to see that both match results and parse positions can
actually be stored on a stack that grows as the parser walks deeper in
the grammar tree and shrinks as it returns. Moreover, if one creates a
new stack for each rule the parser enters, its maximum depth can be
computed statically from the grammar. This allows us to implement the
stack not as an array, but as a set of numbered variables in each
function that handles parsing of a grammar rule, avoiding potentially
slow array accesses.

This commit implements the idea from the previous paragraph, using
separate stack for match results and for parse positions. As a result,
defined variables are reused and unnecessary copying avoided.

Speed implications
------------------

This change speeds up the benchmark suite execution by 2.14%.

Detailed results (benchmark suite totals as reported by "jake benchmark"
on Node.js 0.4.8):

-----------------------------------
 Test #      Before        After
-----------------------------------
      1   129.01 kB/s   131.98 kB/s
      2   129.39 kB/s   130.13 kB/s
      3   128.63 kB/s   132.57 kB/s
      4   127.53 kB/s   129.82 kB/s
      5   127.98 kB/s   131.80 kB/s
-----------------------------------
Average   128.51 kB/s   131.26 kB/s
-----------------------------------

Size implications
-----------------

This change makes a sample of generated parsers 8.60% smaller:

Before:

  $ wc -c src/parser.js examples/*.js
   110867 src/parser.js
    13886 examples/arithmetics.js
   450125 examples/css.js
   632390 examples/javascript.js
    61365 examples/json.js
  1268633 total

After:

  $ wc -c src/parser.js examples/*.js
    99597 src/parser.js
    13077 examples/arithmetics.js
   399893 examples/css.js
   592044 examples/javascript.js
    54797 examples/json.js
  1159408 total
 		13 years ago
..
vendor/qunit Upgrade QUnit to the current master (c532d183664118fc2ca1) 14 years ago
README Add command-line runner for the test suite 14 years ago
checks-test.js Do not pass |global| into wrapping functions in tests, it's useless 14 years ago
compiler-test.js Reset parser position when action returns |null| 13 years ago
helpers.js Add ability to start parsing from any grammar rule 14 years ago
index.html Move test helper into its own file + reorder test file includes 14 years ago
parser-test.js Remove trailing comma in parser tests (IE compatibility) 13 years ago
passes-test.js Rewrite variable handling in generated parsers 13 years ago
run Test and benchmark command-line runners can be run from any directory 14 years ago

README 

PEG.js Test Suite
=================

This is the PEG.js test suite. It ensures PEG.js works correctly. All tests
should always pass on all supported platforms.

Running in a browser
--------------------

  1. Open the index.html file in your browser.

  2. Watch the test pass (or fail).

Running from a command-line
---------------------------

  1. Make sure you have Node.js installed.

  2. Run the following command:

       ./run

  3. Watch the tests pass (or fail).