<%@include file="includes/setup.md.rsp"%>

<%@string fcnname="indexByRow"%>
<% fcnname <- "<%@string name="fcnname"%>" %>
<%@meta title="${fcnname}() benchmarks"%>
<%@meta author="Henrik Bengtsson"%>
<%@meta date="2014-11-09"%>

<%@include file="${header}"%>

<%
lfun <- local({
  locals <- list()
  function(txt = NULL) {
    if (is.null(txt)) return(locals)
    local <- list(txt)
    locals <<- c(locals, local)
  }	 
})
%>

# <%@meta name="title"%>

This report benchmark the performance of `<%=fcnname%>()` against alternative methods:

* `indexByRow_R1()` based in `matrix(..., byrow = TRUE)`
* `indexByRow_R2()` is a modified version of `indexByRow_R1()`

where `indexByRow_R1()` and `indexByRow_R2()` are defined as in the Appendix.

<%
lfun(withCapture({
indexByRow_R1 <- function(dim, idxs = NULL, ...) {
  n <- prod(dim)
  x <- matrix(seq_len(n), nrow = dim[2L], ncol = dim[1L], byrow = TRUE)
  if (!is.null(idxs))
    x <- x[idxs]
  as.vector(x)
} # indexByRow_R1()
}))

lfun(withCapture({
indexByRow_R2 <- function(dim, idxs = NULL, ...) {
  n <- prod(dim)
  if (is.null(idxs)) {
    x <- matrix(seq_len(n), nrow = dim[2L], ncol = dim[1L], byrow = TRUE)
    as.vector(x)
  } else {
    idxs <- idxs - 1
    cols <- idxs %/% dim[2L]
    rows <- idxs  %% dim[2L]
    cols + dim[1L]*rows + 1L
  }
} # indexByRow_R2()
}))
%>


## Data
<% lfun(withCapture({
<%@include file="R/random-matrices.R"%>
})) %>

```r
<%=withCapture({
data <- rmatrices(mode = "index")
})%>
```
where `rmatrices()` is defined in the Appendix.

<%
# data <- data[1:2]
%>

## Results

<% for (dataLabel in names(data)) { %>
<% message(dataLabel) %>
### <%=dataLabel%> matrix


```r
<%=withCapture({
X <- data[[.dataLabel.]]
dim <- dim(X)
idxsList <- list(
  'all-by-NULL'  = NULL,
  all            = seq_len(prod(dim)),
  odd            = seq(from = 1, to = prod(dim), by = 2L)
)
str(idxsList)
})%>
```

<% for (ii in seq_along(idxsList)) { %>

#### Index set '<%=names(idxsList)[ii]%>'
<%
idxs <- idxsList[[ii]]
idxsTag <- names(idxsList)[ii]

# Validate correctness
res <- list(
 indexByRow    = indexByRow(dim, idxs = idxs),
 indexByRow_R1 = indexByRow_R1(dim, idxs = idxs),
 indexByRow_R2 = indexByRow_R2(dim, idxs = idxs)
)
lapply(res, FUN = function(x) stopifnot(all.equal(x, res[[1]])))
gc()
%>

```r
<%=withCapture({
stats <- microbenchmark(
 indexByRow    = indexByRow(dim, idxs = idxs),
 indexByRow_R1 = indexByRow_R1(dim, idxs = idxs),
 indexByRow_R2 = indexByRow_R2(dim, idxs = idxs),
 unit = "ms"
)
})%>
```

<% benchmarkResults(stats, tags=c(dataLabel, idxsTag)) %>

<% } # for (ii ...) %>

<% } # for (dataLabel ...) %>

<%@include file="${footer}"%>

### Local functions
```r
<%=lfun()[[1]]%>
```
```r
<%=lfun()[[2]]%>
```
```r
<%=lfun()[[3]]%>
```


<%---------------------------------------------------------------------------
HISTORY:
2014-06-09
o Created.
---------------------------------------------------------------------------%>