[PATCH v2 6/6] test-tool: add helper for name-hash values

From

Derrick Stolee via GitGitGadget <gitgitgadget@gmail.com>

Date

Sep 18, 2024, 20:46 UTC

Message-ID

<7e47fc8cb53647ad92c86801204c3089a5dfe8e6.1726692382.git.gitgitgadget@gmail.com>

In-Reply-To

<pull.1785.v2.git.1726692381.gitgitgadget@gmail.com>

From: Derrick Stolee <stolee@gmail.com>

[1] https://github.com/microsoft/fluentui

Signed-off-by: Derrick Stolee <stolee@gmail.com>
---
 Makefile                  |  1 +
 t/helper/test-name-hash.c | 23 ++++++++++++++++++++++
 t/helper/test-tool.c      |  1 +
 t/helper/test-tool.h      |  1 +
 t/perf/p5314-name-hash.sh | 41 +++++++++++++++++++++++++++++++++++++++
 t/t5310-pack-bitmaps.sh   | 26 +++++++++++++++++++++++++
 6 files changed, 93 insertions(+)
 create mode 100644 t/helper/test-name-hash.c
 create mode 100755 t/perf/p5314-name-hash.sh

diff --git a/Makefile b/Makefile
index 275a5ee3c9f..50797a4e541 100644
--- a/Makefile
+++ b/Makefile
@@ -812,6 +812,7 @@ TEST_BUILTINS_OBJS += test-lazy-init-name-hash.o
 TEST_BUILTINS_OBJS += test-match-trees.o
 TEST_BUILTINS_OBJS += test-mergesort.o
 TEST_BUILTINS_OBJS += test-mktemp.o
+TEST_BUILTINS_OBJS += test-name-hash.o
 TEST_BUILTINS_OBJS += test-online-cpus.o
 TEST_BUILTINS_OBJS += test-pack-mtimes.o
 TEST_BUILTINS_OBJS += test-parse-options.o
diff --git a/t/helper/test-name-hash.c b/t/helper/test-name-hash.c
new file mode 100644
index 00000000000..15fb8f853c1
--- /dev/null
+++ b/t/helper/test-name-hash.c
@@ -0,0 +1,23 @@
+/*
+ * test-name-hash.c: Read a list of paths over stdin and report on their
+ * name-hash and full name-hash.
+ */
+
+#include "test-tool.h"
+#include "git-compat-util.h"
+#include "pack-objects.h"
+#include "strbuf.h"
+
+int cmd__name_hash(int argc UNUSED, const char **argv UNUSED)
+{
+	struct strbuf line = STRBUF_INIT;
+
+	while (!strbuf_getline(&line, stdin)) {
+		uint32_t name_hash = pack_name_hash(line.buf);
+		uint32_t full_hash = pack_full_name_hash(line.buf);
+
+		printf("%10"PRIu32"\t%10"PRIu32"\t%s\n", name_hash, full_hash, line.buf);
+	}
+
+	return 0;
+}
diff --git a/t/helper/test-tool.c b/t/helper/test-tool.c
index 1ebb69a5dc4..e794058ab6d 100644
--- a/t/helper/test-tool.c
+++ b/t/helper/test-tool.c
@@ -44,6 +44,7 @@ static struct test_cmd cmds[] = {
 	{ "match-trees", cmd__match_trees },
 	{ "mergesort", cmd__mergesort },
 	{ "mktemp", cmd__mktemp },
+	{ "name-hash", cmd__name_hash },
 	{ "online-cpus", cmd__online_cpus },
 	{ "pack-mtimes", cmd__pack_mtimes },
 	{ "parse-options", cmd__parse_options },
diff --git a/t/helper/test-tool.h b/t/helper/test-tool.h
index 21802ac27da..26ff30a5a9a 100644
--- a/t/helper/test-tool.h
+++ b/t/helper/test-tool.h
@@ -37,6 +37,7 @@ int cmd__lazy_init_name_hash(int argc, const char **argv);
 int cmd__match_trees(int argc, const char **argv);
 int cmd__mergesort(int argc, const char **argv);
 int cmd__mktemp(int argc, const char **argv);
+int cmd__name_hash(int argc, const char **argv);
 int cmd__online_cpus(int argc, const char **argv);
 int cmd__pack_mtimes(int argc, const char **argv);
 int cmd__parse_options(int argc, const char **argv);
diff --git a/t/perf/p5314-name-hash.sh b/t/perf/p5314-name-hash.sh
new file mode 100755
index 00000000000..9fe26612fac
--- /dev/null
+++ b/t/perf/p5314-name-hash.sh
@@ -0,0 +1,41 @@
+#!/bin/sh
+
+test_description='Tests pack performance using bitmaps'
+. ./perf-lib.sh
+
+GIT_TEST_PASSING_SANITIZE_LEAK=0
+export GIT_TEST_PASSING_SANITIZE_LEAK
+
+test_perf_large_repo
+
+test_size 'paths at head' '
+	git ls-tree -r --name-only HEAD >path-list &&
+	wc -l <path-list
+'
+
+test_size 'number of distinct name-hashes' '
+	cat path-list | test-tool name-hash >name-hashes &&
+	cat name-hashes | awk "{ print \$1; }" | sort -n | uniq -c >name-hash-count &&
+	wc -l <name-hash-count
+'
+
+test_size 'number of distinct full-name-hashes' '
+	cat name-hashes | awk "{ print \$2; }" | sort -n | uniq -c >full-name-hash-count &&
+	wc -l <full-name-hash-count
+'
+
+test_size 'maximum multiplicity of name-hashes' '
+	cat name-hash-count | \
+		sort -nr | \
+		head -n 1 | \
+		awk "{ print \$1; }"
+'
+
+test_size 'maximum multiplicity of fullname-hashes' '
+	cat full-name-hash-count | \
+		sort -nr | \
+		head -n 1 | \
+		awk "{ print \$1; }"
+'
+
+test_done
diff --git a/t/t5310-pack-bitmaps.sh b/t/t5310-pack-bitmaps.sh
index a6de7c57643..5759710a2cd 100755
--- a/t/t5310-pack-bitmaps.sh
+++ b/t/t5310-pack-bitmaps.sh
@@ -26,6 +26,32 @@ has_any () {
 	grep -Ff "$1" "$2"
 }
 
+# Since name-hash values are stored in the .bitmap files, add a test
+# that checks that the name-hash calculations are stable across versions.
+# Not exhaustive, but these hashing algorithms would be hard to change
+# without causing deviations here.
+test_expect_success 'name-hash value stability' '
+	cat >names <<-\EOF &&
+	first
+	second
+	third
+	one-long-enough-for-collisions
+	two-long-enough-for-collisions
+	EOF
+
+	test-tool name-hash <names >out &&
+
+	cat >expect <<-\EOF &&
+	2582249472	3109209818	first
+	2289942528	3781118409	second
+	2300837888	3028707182	third
+	2544516325	3241327563	one-long-enough-for-collisions
+	2544516325	4207880830	two-long-enough-for-collisions
+	EOF
+
+	test_cmp expect out
+'
+
 test_bitmap_cases () {
 	writeLookupTable=false
 	for i in "$@"

-- 
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