<para> Glasgow Haskell comes with a time and space profiling
system. Its purpose is to help you improve your understanding of
your program's execution behaviour, so you can improve it.</para>
-
+
<para> Any comments, suggestions and/or improvements you have are
welcome. Recommended “profiling tricks” would be
especially cool! </para>
<indexterm><primary><option>-p</option></primary><secondary>RTS
option</secondary></indexterm>
</listitem>
-
+
<listitem>
<para> Examine the generated profiling information, using one of
GHC's profiling tools. The tool to use will depend on the kind
of profiling information generated.</para>
</listitem>
-
+
</orderedlist>
-
+
<sect1 id="cost-centres">
<title>Cost centres and cost-centre stacks</title>
-
+
<para>GHC's profiling system assigns <firstterm>costs</firstterm>
to <firstterm>cost centres</firstterm>. A cost is simply the time
or space required to evaluate an expression. Cost centres are
</listitem>
</varlistentry>
</variablelist>
-
+
<para>There are a few other profiling-related compilation options.
Use them <emphasis>in addition to</emphasis>
<option>-prof</option>. These do not have to be used consistently
it manually.</para>
</listitem>
</varlistentry>
-
+
<varlistentry>
<term>
<option>-auto-all</option>:
</varlistentry>
</variablelist>
-
+
</sect1>
<sect1 id="prof-heap">
file,
<filename><replaceable>prog</replaceable>.ps</filename>. The
<command>hp2ps</command> utility is described in detail in
- <xref linkend="hp2ps"/>.</para>
+ <xref linkend="hp2ps"/>.</para>
</listitem>
<listitem>
<para>Display the heap profile using a postscript viewer such
represent an approximation to the actual type.</para>
</listitem>
</varlistentry>
-
+
<varlistentry>
<term>
<option>-hr</option>
to display a profile by type but only for data produced by a
certain module, or a profile by retainer for a certain type of
data. Restrictions are specified as follows:</para>
-
+
<variablelist>
<varlistentry>
<term>
types.</para>
</listitem>
</varlistentry>
-
+
<varlistentry>
<term>
<option>-hr</option><replaceable>cc</replaceable>,...
state in addition to the space allocated for its stack
(stacks normally start small and then grow as
necessary).</para>
-
+
<para>This includes the main thread, so using
<option>-xt</option> is a good way to see how much stack
space the program is using.</para>
</variablelist>
</sect2>
-
+
<sect2 id="retainer-prof">
<title>Retainer Profiling</title>
set <literal>MANY</literal>. The maximum set size defaults to 8
and can be altered with the <option>-R</option> RTS
option:</para>
-
+
<variablelist>
<varlistentry>
<term><option>-R</option><replaceable>size</replaceable></term>
<screen>
<replaceable>prog</replaceable> +RTS -hr -hcB
</screen>
-
+
<para>This trick isn't foolproof, because there might be other
B closures in the heap which aren't the retainers we are
interested in, but we've found this to be a useful technique
<indexterm><primary>heap profiles</primary></indexterm>
<indexterm><primary>postscript, from heap profiles</primary></indexterm>
<indexterm><primary><option>-h<break-down></option></primary></indexterm>
-
+
<para>Usage:</para>
-
+
<screen>
hp2ps [flags] [<file>[.hp]]
</screen>
<para>The flags are:</para>
<variablelist>
-
+
<varlistentry>
<term><option>-d</option></term>
<listitem>
<para>Use a small box for the title.</para>
</listitem>
</varlistentry>
-
+
<varlistentry>
<term><option>-t<float></option></term>
<listitem>
<para>Generate colour output.</para>
</listitem>
</varlistentry>
-
+
<varlistentry>
<term><option>-y</option></term>
<listitem>
<para>Ignore marks.</para>
</listitem>
</varlistentry>
-
+
<varlistentry>
<term><option>-?</option></term>
<listitem>
heap profile as described in the previous section. Run <command>gv</command> on your
profile:
<screen>
- gv -watch -seascape FOO.ps
+ gv -watch -seascape FOO.ps
</screen>
If you forget the <literal>-watch</literal> flag you can still select
"Watch file" from the "State" menu. Now each time you generate a new
head -`fgrep -n END_SAMPLE FOO.hp | tail -1 | cut -d : -f 1` FOO.hp \
| hp2ps > FOO.ps
kill -HUP $gvpsnum
- done
+ done
</screen>
</para>
</sect2>
a yellow background indicates a part of the program that was
never evaluated; a green background indicates an always-True
expression and a red background indicates an always-False one.
- </para>
+ </para>
<sect2><title>A small example: Reciprocation</title>
</para>
<screen>
-$ ghc -fhpc Recip.hs --make
+$ ghc -fhpc Recip.hs --make
</screen>
<para>HPC index (.mix) files are placed placed in .hpc subdirectory. These can be considered like
- the .hi files for HPC.
+ the .hi files for HPC.
</para>
<screen>
$ ./Recip
$ hpc report Recip
80% expressions used (81/101)
12% boolean coverage (1/8)
- 14% guards (1/7), 3 always True,
- 1 always False,
+ 14% guards (1/7), 3 always True,
+ 1 always False,
2 unevaluated
0% 'if' conditions (0/1), 1 always False
100% qualifiers (0/0)
hpc_index.html, hpc_index_alt.html, hpc_index_exp.html,
hpc_index_fun.html.
</para>
- </sect2>
+ </sect2>
<sect2><title>Options for instrumenting code for coverage</title>
<para>
- Turning on code coverage is easy, use the -fhpc flag.
+ Turning on code coverage is easy, use the -fhpc flag.
Instrumented and non-instrumented can be freely mixed.
When compiling the Main module GHC automatically detects when there
is an hpc compiled file, and adds the correct initialization code.
<para>
The hpc toolkit uses a cvs/svn/darcs-like interface, where a
- single binary contains many function units.</para>
+ single binary contains many function units.</para>
<screen>
-$ hpc
+$ hpc
Usage: hpc COMMAND ...
Commands:
<para>In general, these options act on .tix file after an
instrumented binary has generated it, which hpc acting as a
conduit between the raw .tix file, and the more detailed reports
- produced.
+ produced.
</para>
-
+
<para>
The hpc tool assumes you are in the top-level directory of
the location where you built your application, and the .tix
--srcdir multiple times to analyse programs compiled from
difference locations, as is typical for packages.
</para>
-
+
<para>
We now explain in more details the major modes of hpc.
</para>
all modules and packages are considered in generating report,
unless include or exclude are used. The report is a summary
unless the --per-module flag is used. The --xml-output option
- allows for tools to use hpc to glean coverage.
- </para>
+ allows for tools to use hpc to glean coverage.
+ </para>
<screen>
$ hpc help report
Usage: hpc report [OPTION] .. <TIX_FILE> [<MODULE> [<MODULE> ..]]
</sect3>
<sect3><title>hpc sum</title>
- <para>hpc sum adds together any number of .tix files into a single
- .tix file. hpc sum does not change the original .tix file; it generates a new .tix file.
+ <para>hpc sum adds together any number of .tix files into a single
+ .tix file. hpc sum does not change the original .tix file; it generates a new .tix file.
</para>
<screen>
$ hpc help sum
</screen>
</sect3>
<sect3><title>hpc combine</title>
- <para>hpc combine is the swiss army knife of hpc. It can be
+ <para>hpc combine is the swiss army knife of hpc. It can be
used to take the difference between .tix files, to subtract one
.tix file from another, or to add two .tix files. hpc combine does not
- change the original .tix file; it generates a new .tix file.
+ change the original .tix file; it generates a new .tix file.
</para>
<screen>
$ hpc help combine
</sect3>
<sect3><title>hpc map</title>
<para>hpc map inverts or zeros a .tix file. hpc map does not
- change the original .tix file; it generates a new .tix file.
+ change the original .tix file; it generates a new .tix file.
</para>
<screen>
$ hpc help map
-Usage: hpc map [OPTION] .. <TIX_FILE>
+Usage: hpc map [OPTION] .. <TIX_FILE>
Map a function over a single .tix file
Options:
--hpcdir=DIR sub-directory that contains .mix files
default .hpc [rarely used]
--output=FILE output FILE
-% hpc help draft
+% hpc help draft
Usage: hpc draft [OPTION] .. <TIX_FILE>
Options:
the invocation
<command>foo +RTS -rfoo.ticky</command>.
</para>
-
+
<screen>
foo +RTS -rfoo.ticky
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