Re: macro for fir list?

fir wrote:

fir wrote:

fir wrote:

bart wrote:

On 30/03/2024 09:56, fir wrote:
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>

yet other example
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//bytes container
   char* bytes = NULL; int bytes_size = 0;
   void bytes_add(char val) {
(bytes=(char*)realloc(bytes,++bytes_size*sizeof(char)))[bytes_size-1]=val;
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 }
   void bytes_load(char* name)  {    FILE *f = fopen(name, "rb"); int
c; while((c=getc(f))!=EOF) bytes_add(c);   fclose(f);  }

>
This is pretty inefficient. Loading an 8MB file this way takes 3
seconds, vs. 50ms to load it in one go.
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Loading the same 90KB file 10,000 times took 120 seconds, vs. 0.8
seconds even using a scripting language.
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80% of the inefficiency is growing the buffer one byte at a time. The
other 20% is reading the file one byte at a time.
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i know its inneficient but that was not the point - the point was  more
about composition and utility
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i may revrite but the example would be much longer
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   char* bytes = NULL; int bytes_size = 0;
   char* bytes_resize(char size) {return
bytes=(char*)realloc(bytes,(bytes_size=size)*sizeof(char));  }
   void bytes_add(char val) {
(bytes=(char*)realloc(bytes,++bytes_size*sizeof(char)))[bytes_size-1]=val;
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  }
   void bytes_save(char* name)  {    FILE* f =fopen(name, "wb"); int
saved = fwrite (bytes , 1, bytes_size, f); fclose (f);  }
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>
  int GetFileSize2(char *filename)
  {
     struct stat st;
     if (stat(filename, &st)==0) return (int) st.st_size;
//    ERROR_EXIT("error obtaining file size for &s", filename);
     return -1;
  }
>
   void bytes_load(char* name)
   {
     int flen = GetFileSize2(name);
     FILE *f = fopen(name, "rb");
     int loaded = fread(bytes_resize(flen), 1, flen, f);
     fclose(f);
    }
>
generally if some uses this bytes microcintainer (i call it also list,
though it is also resizable array) one may use thie add method which
callst reallock or call resize(1000) and use it by bytes[i] so its not
inefficient
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//@include "bytes.c"
for(int i=0;i<1000;i++) bytes_add(rand()&0xff);
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bytes_resize(1000);
for(int i=0;i<1000;i++) bytes[i]=rand()&0xff;
>

>
yoy may check how much it last to say insert 1M of bytes by add compared
to resize and put it normall way - thic could measure overhead of this
reallock... i may add this variable say _cached_size or what to name it,
its a line of code ot wo and that will speed up but there still be a
cost of if

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i made some test with putting 1M by add it takes 160 ms
10M by cahced add 45 ms and 10M stright 7 ms, 10M by firs approch may
take more than 10x 160 ms becouse i drwa a plot and if its plots so slow
i dont wait,
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so it would be 160 ns for add() 4.5 ns for cached add() and 0.7 ns for "=" (but as i said it can be longer for reallock bassed add if yet loop is bigger
- this is hovever all side question as it was more on compositiion
and utility of such "fir list" in comparision for example to c++ vector bloat