[Rd] table() and as.character() performance for logical values
Tomas Kalibera
tom@@@k@||ber@ @end|ng |rom gm@||@com
Fri Apr 11 18:01:03 CEST 2025
On 4/11/25 16:23, Suharto Anggono Suharto Anggono via R-devel wrote:
> Alternative revision:
>
> Added to my changed 'StringFromLogical':
> #define CACHE 16
> if (!(*warn & CACHE)) {TrueCh = FalseCh = NULL; *warn |= CACHE;}
>
> No change to 'coerceToString' and 'coerceToSymbol'.
>
> --------------
> On Friday, 11 April 2025 at 08:02:58 pm GMT+7, Suharto Anggono Suharto Anggono <suharto_anggono using yahoo.com> wrote:
>
>
> Oh, with the abuse of 'warn' in my previous message, warning would be issued if the input 'v' of 'coerceToString' is a logical vector of length 1.
>
> Revision:
>
> Added to my changed 'StringFromLogical':
> if (*warn) {TrueCh = FalseCh = NULL; *warn = 0;}
>
> 'coerceToString': insert
> if (i == 0) warn = 1;
> for LGLSXP case or initialize 'warn' to 16
>
> 'coerceToSymbol': insert
> warn = 1;
> for LGLSXP case or initialize 'warn' to 16
>
>
> Another way is following the approach of caching in ''StringFromInteger'.
>
> --------------
> On Friday, 11 April 2025 at 05:05:30 pm GMT+7, Suharto Anggono Suharto Anggono <suharto_anggono using yahoo.com> wrote:
>
>
> On second thought, I wonder if the caching in my changed 'StringFromLogical' in my previous message is safe. While 'ans' in the C function 'coerceToString' is protected, its element is also protected. If the object corresponding to 'ans' is then no longer protected, is it possible for the cached object 'TrueCh' or 'FalseCh' in 'StringFromLogical' to be garbage collected? If it is, I think of clearing the cache for each first filling. For example, by abusing 'warn' argument, the following is added to my changed 'StringFromLogical'.
If this is the caching you had in mind:
> attribute_hidden SEXP StringFromLogical(int x, int *warn)
> {
> static SEXP TrueCh, FalseCh;
> if (x == NA_LOGICAL) return NA_STRING;
> else if (x) return TrueCh ? TrueCh : (TrueCh = mkChar("TRUE"));
> else return FalseCh ? FalseCh : (FalseCh = mkChar("FALSE"));
that is really a protection error. StringFromLogical() should make sure
that TrueCh, FalseCh will be protected as long as recorded in the static
field. PreserveObject() would be a natural function for this.
Best
Tomas
> if (*warn) TrueCh = FalseCh = NULL;
>
> Correspondingly, in 'coerceToString',
>
> warn = i == 0;
>
> is inserted before
>
> SET_STRING_ELT(ans, i, StringFromLogical(LOGICAL_ELT(v, i), &warn));
>
> for LGLSXP case.
>
> ---------------------
> On Thursday, 10 April 2025 at 10:54:03 pm GMT+7, Martin Maechler <maechler using stat.math.ethz.ch> wrote:
>
>
>>>>>> Suharto Anggono Suharto Anggono via R-devel
>>>>>> on Thu, 10 Apr 2025 07:53:04 +0000 (UTC) writes:
> > Chain of calls of C functions in coerce.c for as.character(<logical>) in R:
>
> > do_asatomic
> > ascommon
> > coerceVector
> > coerceToString
> > StringFromLogical (for each element)
>
> > The definition of 'StringFromLogical' in coerce.c :
>
> > Chain of calls of C functions in coerce.c for as.character(<logical>) in R:
> >
> > do_asatomic
> > ascommon
> > coerceVector
> > coerceToString
> > StringFromLogical (for each element)
> >
> > The definition of 'StringFromLogical' in coerce.c :
> >
> > attribute_hidden SEXP StringFromLogical(int x, int *warn)
> > {
> > int w;
> > formatLogical(&x, 1, &w);
> > if (x == NA_LOGICAL) return NA_STRING;
> > else return mkChar(EncodeLogical(x, w));
> > }
> >
> > The definition of 'EncodeLogical' in printutils.c :
> >
> > const char *EncodeLogical(int x, int w)
> > {
> > static char buff[NB];
> > if(x == NA_LOGICAL) snprintf(buff, NB, "%*s", min(w, (NB-1)), CHAR(R_print.na_string));
> > else if(x) snprintf(buff, NB, "%*s", min(w, (NB-1)), "TRUE");
> > else snprintf(buff, NB, "%*s", min(w, (NB-1)), "FALSE");
> > buff[NB-1] = '\0';
> > return buff;
> > }
> >
> > > L <- sample(c(TRUE, FALSE), 10^7, replace = TRUE)
> > > system.time(as.character(L))
> > user system elapsed
> > 2.69 0.02 2.73
> > > system.time(c("FALSE", "TRUE")[L+1])
> > user system elapsed
> > 0.15 0.04 0.20
> > > system.time(c("FALSE", "TRUE")[L+1L])
> > user system elapsed
> > 0.08 0.05 0.13
> > > L <- rep(NA, 10^7)
> > > system.time(as.character(L))
> > user system elapsed
> > 0.11 0.00 0.11
> > > system.time(c("FALSE", "TRUE")[L+1])
> > user system elapsed
> > 0.16 0.06 0.22
> > > system.time(c("FALSE", "TRUE")[L+1L])
> > user system elapsed
> > 0.09 0.03 0.12
> >
> > `as.character` of a logical vector that is all NA is fast enough.
> > It appears that the call to 'formatLogical' inside > the C function
> > 'StringFromLogical' does not introduce much > slowdown.
>
>
> > I found that using string literal inside the C function 'StringFromLogical', by replacing
> > EncodeLogical(x, w)
> > with
> > x ? "TRUE" : "FALSE"
> > (and the call to 'formatLogical' is not needed anymore), make it faster.
>
> indeed! ... and we also notice that the 'w' argument is neither
> needed anymore, and that makes sense: At this point when you
> know you have a an R logical value there are only three
> possibilities and no reason ever to warn about the conversion.
>
> > Alternatively,
> or in addition !
>
>
> > "fast path" could be introduced in 'EncodeLogical', potentially also benefits format() in R.
> > For example, without replacing existing code, the following fragment could be inserted.
> >
> > if(x == NA_LOGICAL) {if(w == R_print.na_width) return CHAR(R_print.na_string);}
> > else if(x) {if(w == 4) return "TRUE";}
> > else {if(w == 5) return "FALSE";}
> >
> > However, with either of them, c("FALSE", "TRUE")[L+1L] is still faster than as.character(L) .
> >
> > Precomputing or caching possible results of the C function 'StringFromLogical' allows as.character(L) to be as fast as c("FALSE", "TRUE")[L+1L] in R. For example, 'StringFromLogical' could be changed to
> >
> > attribute_hidden SEXP StringFromLogical(int x, int *warn)
> > {
> > static SEXP TrueCh, FalseCh;
> > if (x == NA_LOGICAL) return NA_STRING;
> > else if (x) return TrueCh ? TrueCh : (TrueCh = mkChar("TRUE"));
> > else return FalseCh ? FalseCh : (FalseCh = mkChar("FALSE"));
>
> > }
>
> Indeed, and something along this line (storing the other two constant strings) was also
> my thought when seeing the
> mkChar(x ? "TRUE" : "FALSE)
> you implicitly proposed above.
>
> I'm looking into applying both speedups;
> thank you very much, Suharto!
>
> Martin
>
>
> --
> Martin Maechler
> ETH Zurich and R Core team
> [[alternative HTML version deleted]]
>
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