Profile Output Processing Tools for R.

PROFILE OUTPUT PROCESSING TOOLS FOR R

This package provides some simple tools for examining Rprof output and, in particular, extracting and viewing call graph information. Call graph information, including which direct calls where observed and how much time was spent in these calls, can be very useful in identifying performance bottlenecks.

One important caution: because of lazy evaluation a nested call f(g(x)) will appear on the profile call stack as if g had been called by f or one of f's callees, because it is the point at which the value of g(x) is first needed that triggers the evaluation.

EXPORTED FUNCTIONS

The package exports these functions:

• readProfileData reads the data in the file produced by Rprof into a data structure used by the other functions in the package. The format of the data structure is subject to change.

• flatProfile is similar to summaryRprof. It returns either a matrix with output analogous to gprof's flat profile or a matrix like the by.total component returned by summaryRprof; which is returned depends on the value of an optional second argument.

• printProfileCallGraph produces a printed representation of the call graph. It is analogous to the call graph produced by gprof with a few minor changes. Reading the gprof manual section on the call graph should help understanding this output. The output is similar enough to gprof output for the cgprof (http://mvertes.free.fr/) script to be able to produce a call graph via Graphviz.

• profileCallGraph2Dot prints out a Graphviz .dot file representing the profile graph. Times spent in calls can be mapped to node and edge colors. The resulting files can then be viewed with the Graphviz command line tools.

• plotProfileCallGraph uses the graph and Rgraphviz packages to produce call graph visualizations within R. You will need to install these packages to use this function.

• Additional summary functions: funSummary, callSummary, pathSummary, srcSummary, and hotPaths.

• Additional functions: filterProfileData, flameGraph, calleeTreeMapannotateSource, and profileExpr.

EXPORTED VARIABLES

The package also exports two variables:

• plain.style
• google.style

These are style specifications to be used with the call graph display functions plotProfileCallGraph and profileCallGraph2Dot.

A SIMPLE EXAMPLE

Collect profile information for the examples for glm:

Rprof("glm.out")
example(glm)
Rprof()
pd <- readProfileData("glm.out")

Obtain flat profile information:

flatProfile(pd)
flatProfile(pd, FALSE)

Obtain hot paths information:

hotPaths(pd, maxdepth = 10)

Summaries can be obtained in a similar way:

funSummary(pd)
callSummary(pd)
pathSummary(pd)

Obtain a printed call graph on the standard output:

printProfileCallGraph(pd)

If you have the cgprof script and the Graphviz command line tools available on a UNIX-like system, then you can save the printed graph to a file,

printProfileCallGraph(pd, "glm.graph")

and either use

cgprof -TX glm.graph

to display the graph in the interactive graph viewer dotty, or use

cgprof -Tps glm.graph > glm.ps
gv glm.ps

to create a PostScript version of the call graph and display it with gv.

Instead of using the printed graph and cgprof you can create a Graphviz .dot file representation of the call graph with

profileCallGraph2Dot(pd, filename = "glm.dot", score = "total")

and view the graph interactively with dotty using

dotty glm.dot

or as a postscript file with

dot -Tps glm.dot > glm.ps
gv glm.ps

You can also write the profile data to a callgrind file to use with kcachegrind or qcachegrind

writeCallgrindFile(pd, file = "Rprof.cg")

If you have the packages graph and Rgraphviz from Bioconductor installed, then you can view the call graph within R using

plotProfileCallGraph(pd, score = "total")

Both plotProfileCallGraph and profileCallGraph2Dot accept many parameters for adjusting features of the display. You can specify these parameters individually or with a single style parameter. For example,

plotProfileCallGraph(pd, style = google.style)

displays the call graph in a style similar to the one used by the pprof tool in the Google Performance Tools suite.

Similarly, you can plot a flame graph and callee tree map using

flameGraph(pd)
calleeTreeMap(pd)

Finally, you can filter the profile data by selecting or dropping certain functions. For example,

filteredPD <- filterProfileData(pd, select = "anova", focus = TRUE)

Now you can use filteredPD in you calls to summaries functions or plots, for example

hotPaths(filteredPD, maxdepth = 10)
flameGraph(filteredPD)

OPEN ISSUES

My intention was to handle cycles roughly the same way that gprof does. I am not completely sure that I have managed to do this; I am also not completely sure this is the best approach.

The graphs produced by cgprof and by plotProfileGraph and friends when mergeEdges is false differ a bit. I think this is due to the heuristics of cgprof not handling cycle entries ideally and that the plotProfileGraph graphs are actually closer to what is wanted. When mergeEdges is true the resulting graphs are DAGs, which simplifies interpretation, but at the cost of lumping all cycle members together.

gprof provides options for pruning graph printouts by omitting specified nodes. It may be useful to allow this here as well.