[PATCH 1/2] perf: compare diff algorithms

8c912ee (teach --histogram to diff, 2011-07-12) claimed histogram diff
was faster than both Myers and patience.

We have since incorporated a performance testing framework, so add a
test that compares the various diff tasks performed in a real 'log -p'
workload.  This does indeed show that histogram diff slightly beats
Myers, while patience is much slower than the others.

Signed-off-by: Thomas Rast <redacted>
---

The 3000 is pretty arbitrary but makes for a nice test duration.

I'm reluctant to put numbers into the message, since the whole point
of the perf test framework is that you can easily get them too.  But
here's what I'm seeing:

  4000.1: log -3000 (baseline)          0.04(0.02+0.01)                                                     
  4000.2: log --raw -3000 (tree-only)   0.49(0.38+0.09)                                                     
  4000.3: log -p -3000 (Myers)          1.93(1.75+0.17)
  4000.4: log -p -3000 --histogram      1.90(1.74+0.15)
  4000.5: log -p -3000 --patience       2.25(2.07+0.16)

 t/perf/p4000-diff-algorithms.sh |   29 +++++++++++++++++++++++++++++
 1 file changed, 29 insertions(+)
 create mode 100755 t/perf/p4000-diff-algorithms.sh

diff --git a/t/perf/p4000-diff-algorithms.sh b/t/perf/p4000-diff-algorithms.sh
new file mode 100755
index 0000000..d6e505c
--- /dev/null
+++ b/t/perf/p4000-diff-algorithms.sh

@@ -0,0 +1,29 @@
+#!/bin/sh
+
+test_description="Tests diff generation performance"
+
+. ./perf-lib.sh
+
+test_perf_default_repo
+
+test_perf 'log -3000 (baseline)' '
+	git log -1000 >/dev/null
+'
+
+test_perf 'log --raw -3000 (tree-only)' '
+	git log --raw -3000 >/dev/null
+'
+
+test_perf 'log -p -3000 (Myers)' '
+	git log -p -3000 >/dev/null
+'
+
+test_perf 'log -p -3000 --histogram' '
+	git log -p -3000 --histogram >/dev/null
+'
+
+test_perf 'log -p -3000 --patience' '
+	git log -p -3000 --patience >/dev/null
+'
+
+test_done

-- 
1.7.9.2.467.g7fee4