Doc: CG - Tightening up of the Bug Squad intro

[lilypond.git] / Documentation / contributor / regressions.itexi

diff --git a/Documentation/contributor/regressions.itexi b/Documentation/contributor/regressions.itexi
index aa5aeaa4e6a583b7365f95a0a156d67864ea0c83..365582e87f7a8beef00a6e437f67d7b005fba98a 100644 (file)
--- a/Documentation/contributor/regressions.itexi
+++ b/Documentation/contributor/regressions.itexi
@@ -7,6 +7,7 @@
 * Precompiled regression tests::
 * Compiling regression tests::
 * Regtest comparison::
 * Precompiled regression tests::
 * Compiling regression tests::
 * Regtest comparison::

+* Pixel-based regtest comparison::

 * Finding the cause of a regression::
 * Memory and coverage tests::
 * MusicXML tests::
 * Finding the cause of a regression::
 * Memory and coverage tests::
 * MusicXML tests::


@@ -99,8 +100,20 @@ verify that the regression tests have, in fact, run.}
 
 The test comparison shows all of the changes that occurred between
 the current release and the prior release.  Each test that has a
 
 The test comparison shows all of the changes that occurred between
 the current release and the prior release.  Each test that has a

-significant difference in output is displayed, with the old
-version on the left and the new version on the right.
+significant (noticeable) difference in output is displayed, with
+the old version on the left and the new version on the right.
+
+Some of the small changes can be ignored (slightly different slur
+shapes, small variations in note spacing), but this is not always
+the case: sometimes even the smallest change means that something
+is wrong.  To help in distinguishing these cases, we use bigger
+staff size when small differences matter.
+
+Staff size 30 generally means "pay extra attention to details".
+Staff size 40 (two times bigger than default size) or more means
+that the regtest @strong{is} about the details.
+
+Staff size smaller than default doesn't mean anything.

 
 Regression tests whose output is the same for both versions are
 not shown in the test comparison.
 
 Regression tests whose output is the same for both versions are
 not shown in the test comparison.


@@ -123,6 +136,11 @@ something is suspicious!
 @item
 Profile files: give information about
 TODO?  I don't know what they're for.
 @item
 Profile files: give information about
 TODO?  I don't know what they're for.

+Apparently they give some information about CPU usage.  If you got
+tons of changes in cell counts, this probably means that you compiled
+@code{make test-baseline} with a different amount of CPU threads than
+@code{make check}. Try redoing tests from scratch with the same
+number of threads each time -- see @ref{Saving time with the -j option}.

 
 @end itemize
 
 
 @end itemize
 


@@ -183,7 +201,8 @@ than building the source code, as described in
 @node Regtest comparison
 @section Regtest comparison
 
 @node Regtest comparison
 @section Regtest comparison
 

-Before modified code is committed to master, a regression test
+Before modified code is committed to @code{master} (via @code{staging}),
+a regression test

 comparison must be completed to ensure that the changes have
 not caused problems with previously working code.  The comparison
 is made automatically upon compiling the regression test suite
 comparison must be completed to ensure that the changes have
 not caused problems with previously working code.  The comparison
 is made automatically upon compiling the regression test suite


@@ -196,7 +215,7 @@ Run @code{make} with current git master without any of your changes.
 
 @item
 Before making changes to the code, establish a baseline for the comparison by
 
 @item
 Before making changes to the code, establish a baseline for the comparison by

-going to the @file{lilypond-git/build/} directory and running:
+going to the @file{$LILYPOND_GIT/build/} directory and running:

 
 @example
 make test-baseline
 
 @example
 make test-baseline


@@ -280,6 +299,58 @@ and want to do regtests comparison for all of them, you can
 @code{make test-clean}, @code{make} and @code{make check} it without doing
 @code{make test-baseline} again.}
 
 @code{make test-clean}, @code{make} and @code{make check} it without doing
 @code{make test-baseline} again.}
 

+@node Pixel-based regtest comparison
+@section Pixel-based regtest comparison
+
+As an alternative to the @code{make test} method for regtest checking (which
+relies upon @code{.signature} files created by a LilyPond run and which describe
+the placing of grobs) there is a script which compares the output of two
+LilyPond versions pixel-by-pixel.  To use this, start by checking out the
+version of LilyPond you want to use as a baseline, and run @code{make}.  Then,
+do the following:
+
+@example
+cd $LILYPOND_GIT/scripts/auxiliar/
+./make-regtest-pngs.sh -j9 -o
+@end example
+
+The @code{-j9} option tells the script to use 9 CPUs to create the
+images - change this to your own CPU count+1.  @code{-o} means this is the "old"
+version.  This will create images of all the regtests in
+
+@example
+$LILYPOND_BUILD_DIR/out-png-check/old-regtest-results/
+@end example
+
+Now checkout the version you want to compare with the baseline.  Run
+@code{make} again to recreate the LilyPond binary.  Then, do the following:
+
+@example
+cd $LILYPOND_GIT/scripts/auxiliar/
+./make-regtest-pngs.sh -j9 -n
+@end example
+
+The @code{-n} option tells the script to make a "new" version of the
+images.  They are created in
+
+@example
+$LILYPOND_BUILD_DIR/out-png-check/new-regtest-results/
+@end example
+
+Once the new images have been created, the script compares the old images with
+the new ones pixel-by-pixel and prints a list of the different images to the
+terminal, together with a count of how many differences were found.  The
+results of the checks are in
+
+@example
+$LILYPOND_BUILD_DIR/out-png-check/regtest-diffs/
+@end example
+
+To check for differences, browse that directory with an image
+viewer.  Differences are shown in red.  Be aware that some images with complex
+fonts or spacing annotations always display a few minor differences.  These can
+safely be ignored.
+

 
 @node Finding the cause of a regression
 @section Finding the cause of a regression
 
 @node Finding the cause of a regression
 @section Finding the cause of a regression


@@ -485,13 +556,15 @@ a small @file{.ly} file demonstrating the problem was added to the regression
 tests as a proof that the fix works.  If someone will accidentally break
 breve width again, we will notice this in the output of that regression test.
 
 tests as a proof that the fix works.  If someone will accidentally break
 breve width again, we will notice this in the output of that regression test.
 

-We are asking you to help us by checking a regtest or two from time to time.
+@subheading How can I help?
+
+We ask you to help us by checking one or two regtests from time to time.

 You don't need programming skills to do this, not even LilyPond skills -
 just basic music notation knowledge; checking one regtest takes less than
 a minute.  Simply go here:
 
 @example
 You don't need programming skills to do this, not even LilyPond skills -
 just basic music notation knowledge; checking one regtest takes less than
 a minute.  Simply go here:
 
 @example

-@uref{http://www.holmessoft.co.uk/homepage/private/regtests/}
+@uref{http://www.philholmes.net/lilypond/regtests/}

 @end example
 
 @subheading Some tips on checking regtests
 @end example
 
 @subheading Some tips on checking regtests


@@ -505,6 +578,7 @@ or @rinternalsnamed{Top, Internals Reference}.
 Vague descriptions (like "behaves well", "looks reasonable") shouldn't be used.
 
 @ignore
 Vague descriptions (like "behaves well", "looks reasonable") shouldn't be used.
 
 @ignore

+this may be useful for advanced regtest checking

 @subsubheading Is regtest straightforward and systematic?
 
 Unfortunately some regtests are written poorly.  A good regtest should be
 @subsubheading Is regtest straightforward and systematic?
 
 Unfortunately some regtests are written poorly.  A good regtest should be