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chin and chmatch length 1 speedup #4121

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Dec 17, 2019
Merged

chin and chmatch length 1 speedup #4121

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205ff54
added length 1 easier case
mattdowle Dec 17, 2019
a416430
news item
mattdowle Dec 17, 2019
58446bf
re-sort is_utc table
Dec 17, 2019
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2 changes: 2 additions & 0 deletions NEWS.md
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Expand Up @@ -6,6 +6,8 @@

## NEW FEATURES

1. `%chin%` and `chmatch(x, table)` are faster when `x` is length 1, `table` is long, and `x` occurs near the start of `table`. Thanks to Michael Chirico for the suggestion, [#4117](https:/Rdatatable/data.table/pull/4117#discussion_r358378409).

## BUG FIXES

1. A NULL timezone on POSIXct was interpreted by `as.IDate` and `as.ITime` as UTC rather than the session's default timezone (`tz=""`) , [#4085](https:/Rdatatable/data.table/issues/4085).
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4 changes: 2 additions & 2 deletions R/utils.R
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Expand Up @@ -119,8 +119,8 @@ do_patterns = function(pat_sub, all_cols) {

# check UTC status
is_utc = function(tz) {
# via grep('UTC|GMT', OlsonNames(), value = TRUE)
utc_tz = c("Etc/GMT", "Etc/UTC", "GMT", "GMT-0", "GMT+0", "GMT0", "UTC")
# via grep('UTC|GMT', OlsonNames(), value = TRUE); ordered by "prior" frequency
utc_tz = c("UTC", "GMT", "Etc/UTC", "Etc/GMT", "GMT-0", "GMT+0", "GMT0")
if (is.null(tz)) tz = Sys.timezone()
return(tz %chin% utc_tz)
}
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29 changes: 21 additions & 8 deletions src/chmatch.c
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Expand Up @@ -4,17 +4,31 @@ static SEXP chmatchMain(SEXP x, SEXP table, int nomatch, bool chin, bool chmatch
if (!isString(x) && !isNull(x)) error("x is type '%s' (must be 'character' or NULL)", type2char(TYPEOF(x)));
if (!isString(table) && !isNull(table)) error("table is type '%s' (must be 'character' or NULL)", type2char(TYPEOF(table)));
if (chin && chmatchdup) error("Internal error: either chin or chmatchdup should be true not both"); // # nocov
// allocations up front before savetl starts
SEXP ans = PROTECT(allocVector(chin?LGLSXP:INTSXP, length(x)));
if (!length(x)) { UNPROTECT(1); return ans; } // no need to look at table when x is empty
const int xlen = length(x);
const int tablelen = length(table);
// allocations up front before savetl starts in case allocs fail
SEXP ans = PROTECT(allocVector(chin?LGLSXP:INTSXP, xlen));
if (xlen==0) { UNPROTECT(1); return ans; } // no need to look at table when x is empty
int *ansd = INTEGER(ans);
if (!length(table)) { const int val=(chin?0:nomatch), n=LENGTH(x); for (int i=0; i<n; ++i) ansd[i]=val; UNPROTECT(1); return ans; }
if (tablelen==0) { const int val=(chin?0:nomatch), n=xlen; for (int i=0; i<n; ++i) ansd[i]=val; UNPROTECT(1); return ans; }
// Since non-ASCII strings may be marked with different encodings, it only make sense to compare
// the bytes under a same encoding (UTF-8) #3844 #3850
const SEXP *xd = STRING_PTR(PROTECT(coerceUtf8IfNeeded(x)));
const SEXP *td = STRING_PTR(PROTECT(coerceUtf8IfNeeded(table)));
const int nprotect = 3; // ans, xd, td
if (xlen==1) {
ansd[0] = nomatch;
for (int i=0; i<tablelen; ++i) {
if (td[i]==xd[0]) {
ansd[0] = chin ? 1 : i+1;
break; // short-circuit early; if there are dups in table the first is returned
}
}
UNPROTECT(nprotect);
return ans;
}
// else xlen>1; nprotect is const above since no more R allocations should occur after this point
savetl_init();
const int xlen = length(x);
for (int i=0; i<xlen; i++) {
SEXP s = xd[i];
const int tl = TRUELENGTH(s);
Expand All @@ -31,7 +45,6 @@ static SEXP chmatchMain(SEXP x, SEXP table, int nomatch, bool chin, bool chmatch
// # nocov end
}
}
const int tablelen = length(table);
int nuniq=0;
for (int i=0; i<tablelen; ++i) {
SEXP s = td[i];
Expand Down Expand Up @@ -89,8 +102,8 @@ static SEXP chmatchMain(SEXP x, SEXP table, int nomatch, bool chin, bool chmatch
for (int i=0; i<tablelen; i++)
SET_TRUELENGTH(td[i], 0); // reinstate 0 rather than leave the -i-1
savetl_end();
UNPROTECT(3); // ans, xd, td
return(ans);
UNPROTECT(nprotect); // ans, xd, td
return ans;
}

// for internal use from C :
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