Comparing two matrices, row by row

ar1 <- array(data=c(1:16),dim=c(4,4))
ar2 <- array(data=c(1,2,3,3,5:16),dim=c(4,4))
z<-ar1==ar2
ar1
[,1] [,2] [,3] [,4]
[1,] 1 5 9 13
[2,] 2 6 10 14
[3,] 3 7 11 15
[4,] 4 8 12 16
ar2
[,1] [,2] [,3] [,4]
[1,] 1 5 9 13
[2,] 2 6 10 14
[3,] 3 7 11 15
[4,] 3 8 12 16
z
[,1] [,2] [,3] [,4]
[1,] TRUE TRUE TRUE TRUE
[2,] TRUE TRUE TRUE TRUE
[3,] TRUE TRUE TRUE TRUE
[4,] FALSE TRUE TRUE TRUE
which(z==FALSE)
[1] 4

Or

apply(ar1==ar2,1,all)