> On 4 Nov 2016, at 16:41, Jeff Newmiller <jdnew...@dcn.davis.ca.us> wrote:
>
> Sara wins on memory use.
>
> Rui wins on speed.
>
> Bert wins on clarity.
>
> library(microbenchmark)
>
> N <- 1000
> x <- matrix( runif( N*N ), ncol=N )
> y <- seq.int( N )
>
> microbenchmark( { t( y * t(x) ) }
> , { x %*% diag( y ) }
> , { sweep( x, 2, y, `*` ) }
> )
> Unit: milliseconds
> expr min lq median uq max
> neval
> { t(y * t(x)) } 6.659562 7.475414 7.871341 8.182623 47.01105
> 100
> { x %*% diag(y) } 9.859292 11.014021 11.281334 11.733825 48.79463
> 100
> { sweep(x, 2, y, `*`) } 16.535938 17.682175 18.283572 18.712342 55.47159
> 100
I get different results with R3.2.2 on Mac OS X (using reference BLAS).
library(rbenchmark)
N <- 1000
x <- matrix( runif( N*N ), ncol=N )
y <- seq.int( N )
benchmark( t( y * t(x) ), x %*% diag( y ), sweep( x, 2, y, `*` ) ,
columns=c("test","elapsed","relative"), replications=10
)
# test elapsed relative
# 3 sweep(x, 2, y, `*`) 0.132 1.000
# 1 t(y * t(x)) 0.189 1.432
# 2 x %*% diag(y) 7.928 60.061
library(microbenchmark)
microbenchmark( { t( y * t(x) ) }
, { x %*% diag( y ) }
, { sweep( x, 2, y, `*` ) },
times=10, unit="s"
)
# Unit: seconds
# expr min lq mean median uq
max neval cld
# { t(y * t(x)) } 0.01099410 0.01132096 0.01597058 0.01332414
0.01430672 0.04447432 10 a
# { x %*% diag(y) } 0.76588887 0.78581717 0.79878255 0.79811626
0.80607877 0.82903945 10 b
# { sweep(x, 2, y, `*`) } 0.01177478 0.01246777 0.01409457 0.01314718
0.01600818 0.01802171 10 a
sweep appears to very good.
I don't quite understand why I get a very different ranking.
Berend
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