Performance Issue on a Nested JSON example

[soasme]

PeppaPEG version: 1.2.0.

Given program, half of the execution time spent on NeedLoosen. We should optimize it.

$ cat examples/json.c
#include <stdio.h>
#include <stdlib.h>
#include "../peppapeg.h"
#include "json.h"

# define NESTING_DEPTH          1000

int main(int argc, char* argv[]) {
    char* input = malloc(sizeof(char) * (NESTING_DEPTH*2 + 1));
    int i;

    for (i = 0; i < NESTING_DEPTH; i++) {
        input[i] = '[';
        input[NESTING_DEPTH+i] = ']';
    }
    input[NESTING_DEPTH*2] = '\0';

    P4_Grammar* grammar = P4_CreateJSONGrammar();
    P4_Source* source = P4_CreateSource(input, P4_JSONEntry);

    printf("%u\n", P4_Parse(grammar, source));

    free(input);
    P4_DeleteSource(source);
    P4_DeleteGrammar(grammar);

    return 0;
}

Run it with valgrind:

$ gcc -g  peppapeg.c examples/json.c && valgrind --tool=callgrind ./a.out
$ callgrind_annotate callgrind.out.63642

We have below profiling result:

--------------------------------------------------------------------------------
Ir
--------------------------------------------------------------------------------
1,265,470,759 (100.0%)  PROGRAM TOTALS

--------------------------------------------------------------------------------
Ir                    file:function
--------------------------------------------------------------------------------
706,187,168 (55.80%)  peppapeg.c:P4_NeedLoosen [/app/a.out]
320,620,450 (25.34%)  peppapeg.c:P4_IsTight [/app/a.out]
170,320,160 (13.46%)  peppapeg.c:P4_IsScoped [/app/a.out]
 25,020,000 ( 1.98%)  peppapeg.c:P4_NeedSquash [/app/a.out]
 10,000,000 ( 0.79%)  peppapeg.c:P4_IsSquashed [/app/a.out]
  4,617,160 ( 0.36%)  ???:_int_free [/usr/lib64/libc-2.28.so]
  3,382,226 ( 0.27%)  ???:malloc [/usr/lib64/ld-2.28.so]
  2,727,160 ( 0.22%)  peppapeg.c:P4_Match'2 [/app/a.out]
  1,925,056 ( 0.15%)  ???:__strlen_avx2 [/usr/lib64/libc-2.28.so]
  1,848,485 ( 0.15%)  ???:free [/usr/lib64/ld-2.28.so]
  1,841,351 ( 0.15%)  peppapeg.c:P4_MatchLiteral [/app/a.out]
  1,705,988 ( 0.13%)  peppapeg.c:P4_MatchChoice'2 [/app/a.out]
  1,540,594 ( 0.12%)  peppapeg.c:P4_IsRule [/app/a.out]
  1,518,598 ( 0.12%)  peppapeg.c:P4_Expression_dispatch'2 [/app/a.out]

$ time ./a.out
real	0m0.157s
user	0m0.154s
sys	0m0.002s

A full profiling result can be seen here: https://gist.github.com/soasme/38471063511aa14302e5ccad173767de

[soasme]

The performance of Current HEAD is 10x faster than v1.2.0:

$ time ./a.out

real	0m0.011s
user	0m0.007s
sys	0m0.003s

--------------------------------------------------------------------------------
Ir
--------------------------------------------------------------------------------
33,294,688 (100.0%)  PROGRAM TOTALS

--------------------------------------------------------------------------------
Ir                  file:function
--------------------------------------------------------------------------------
5,259,163 (15.80%)  ???:_int_free [/usr/lib64/libc-2.28.so]
3,846,555 (11.55%)  ???:malloc [/usr/lib64/ld-2.28.so]
2,595,108 ( 7.79%)  peppapeg.c:P4_Match'2 [/app/a.out]
2,078,669 ( 6.24%)  ???:free [/usr/lib64/ld-2.28.so]
1,841,351 ( 5.53%)  peppapeg.c:P4_MatchLiteral [/app/a.out]
1,805,004 ( 5.42%)  ???:__strlen_avx2 [/usr/lib64/libc-2.28.so]
1,705,988 ( 5.12%)  peppapeg.c:P4_MatchChoice'2 [/app/a.out]
1,518,598 ( 4.56%)  peppapeg.c:P4_Expression_dispatch'2 [/app/a.out]
1,260,936 ( 3.79%)  ???:strdup [/usr/lib64/ld-2.28.so]
1,174,097 ( 3.53%)  peppapeg.c:P4_MatchRepeat [/app/a.out]
1,092,247 ( 3.28%)  peppapeg.c:P4_RaiseError [/app/a.out]
1,003,802 ( 3.01%)  ???:__memcpy_avx_unaligned_erms [/usr/lib64/libc-2.28.so]
  900,542 ( 2.70%)  peppapeg.c:P4_MatchSequence'2 [/app/a.out]
  806,160 ( 2.42%)  peppapeg.c:P4_RescueError [/app/a.out]
  805,790 ( 2.42%)  peppapeg.c:P4_PushFrame [/app/a.out]
  791,322 ( 2.38%)  peppapeg.c:P4_GetPosition [/app/a.out]
  743,611 ( 2.23%)  ???:_int_malloc [/usr/lib64/libc-2.28.so]
  671,409 ( 2.02%)  peppapeg.c:P4_DeleteToken [/app/a.out]
  440,200 ( 1.32%)  peppapeg.c:P4_SetPosition [/app/a.out]
  414,244 ( 1.24%)  peppapeg.c:P4_MatchReference'2 [/app/a.out]
  410,080 ( 1.23%)  peppapeg.c:P4_RemainingText [/app/a.out]
  310,279 ( 0.93%)  peppapeg.c:P4_PopFrame [/app/a.out]
  297,096 ( 0.89%)  ???:__memcmp_avx2_movbe [/usr/lib64/libc-2.28.so]
  210,129 ( 0.63%)  peppapeg.c:P4_GetWhitespaces [/app/a.out]
  196,095 ( 0.59%)  peppapeg.c:P4_GetReference [/app/a.out]
  185,000 ( 0.56%)  peppapeg.c:P4_MatchSpacedExpressions [/app/a.out]
  140,100 ( 0.42%)  ???:0x0000000004c4e760 [???]
  140,100 ( 0.42%)  ???:0x0000000004c4e820 [???]
  140,100 ( 0.42%)  ???:0x0000000004c4e880 [???]
  122,000 ( 0.37%)  peppapeg.c:P4_NeedLift [/app/a.out]
   90,144 ( 0.27%)  peppapeg.c:cleanup_freep [/app/a.out]

The result shows the performance has been improved significantly. Close the issue.