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C vs base R
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.which_min = inline::cfunction( | |
sig = signature("vec" = "SEXP"), | |
body = ' | |
int* v = INTEGER(vec); | |
int min = v[0]; | |
size_t index = 1; | |
size_t n = (size_t) XLENGTH(vec); | |
for(int i = 0; i < n; i++){ | |
if(v[i] < min){ | |
min = v[i]; | |
index = i + 1; | |
} | |
} | |
SEXP r = PROTECT(Rf_allocVector(INTSXP, 2)); | |
INTEGER(r)[0] = min; | |
INTEGER(r)[1] = index; | |
UNPROTECT(1); | |
return r; | |
', | |
language = "C", | |
convention = ".Call" | |
) | |
which_min_c = function(x){ | |
x = as.integer(x) | |
y = .which_min(x) | |
names(y) = c("min", "index") | |
y | |
} | |
which_min_b = function(x){ | |
i = which.min(x) | |
m = x[i] | |
c("min" = m, "index" = i) | |
} | |
s = sample.int(n = 100000, size = 1e8, replace = TRUE) | |
s1 = s; s1[1] = 0L | |
s2 = s; s2[length(s) %/% 2] = 0L | |
s3 = s; s3[length(s)] = 0L | |
microbenchmark::microbenchmark( | |
which.min(s1), which_min_c(s1), which_min_b(s1) | |
) | |
microbenchmark::microbenchmark( | |
which.min(s2), which_min_c(s2), which_min_b(s2) | |
) | |
microbenchmark::microbenchmark( | |
which.min(s3), which_min_c(s3), which_min_b(s3) | |
) |
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