From 3000b5b1f1fe44cc8a23ca34540c1de4381ada83 Mon Sep 17 00:00:00 2001
From: David Reiss <dreiss@apache.org>
Date: Mon, 31 Mar 2008 21:38:29 +0000
Subject: [PATCH] Add an experiment to measure the likeliness that realloc will
 avoid a copy.

git-svn-id: https://svn.apache.org/repos/asf/incubator/thrift/trunk@665625 13f79535-47bb-0310-9956-ffa450edef68
---
 test/cpp/realloc/Makefile       | 21 ++++++++
 test/cpp/realloc/realloc_test.c | 88 +++++++++++++++++++++++++++++++++
 2 files changed, 109 insertions(+)
 create mode 100644 test/cpp/realloc/Makefile
 create mode 100644 test/cpp/realloc/realloc_test.c

diff --git a/test/cpp/realloc/Makefile b/test/cpp/realloc/Makefile
new file mode 100644
index 00000000..57ffb87b
--- /dev/null
+++ b/test/cpp/realloc/Makefile
@@ -0,0 +1,21 @@
+# This probably should not go into "make check", because it is an experiment,
+# not a test.  Specifically, it is meant to determine how likely realloc is
+# to avoid a copy.  This is poorly documented.
+
+run: realloc_test
+	for it in 1 4 64 ; do \
+		for nb in 1 8 64 512 ; do \
+			for mins in 64 512 ; do \
+				for maxs in 2048 262144 ; do \
+					for db in 8 64 ; do \
+						./realloc_test $$nb $$mins $$maxs $$db $$it \
+					; done \
+				; done \
+			; done \
+		; done \
+	; done \
+	> raw_stats
+
+CFLAGS = -Wall -g -std=c99
+LDLIBS = -ldl
+realloc_test: realloc_test.c
diff --git a/test/cpp/realloc/realloc_test.c b/test/cpp/realloc/realloc_test.c
new file mode 100644
index 00000000..7a382b1d
--- /dev/null
+++ b/test/cpp/realloc/realloc_test.c
@@ -0,0 +1,88 @@
+#define _GNU_SOURCE
+#include <stdlib.h>
+#include <stdio.h>
+#include <time.h>
+#include <dlfcn.h>
+
+int copies;
+int non_copies;
+
+void *realloc(void *ptr, size_t size) {
+  static void *(*real_realloc)(void*, size_t) = NULL;
+  if (real_realloc == NULL) {
+    real_realloc = (void* (*) (void*, size_t)) dlsym(RTLD_NEXT, "realloc");
+  }
+
+  void *ret_ptr = (*real_realloc)(ptr, size);
+
+  if (ret_ptr == ptr) {
+    non_copies++;
+  } else {
+    copies++;
+  }
+
+  return ret_ptr;
+}
+
+
+struct TMemoryBuffer {
+  void* ptr;
+  int size;
+};
+
+int main(int argc, char *argv[]) {
+  int num_buffers;
+  int init_size;
+  int max_size;
+  int doublings;
+  int iterations;
+
+  if (argc < 6 ||
+      argc > 7 ||
+      (num_buffers = atoi(argv[1])) == 0 ||
+      (init_size = atoi(argv[2])) == 0 ||
+      (max_size = atoi(argv[3])) == 0 ||
+      init_size > max_size ||
+      (iterations = atoi(argv[4])) == 0 ||
+      (doublings = atoi(argv[5])) == 0 ||
+      (argc == 7 && atoi(argv[6]) == 0)) {
+    fprintf(stderr, "usage: realloc_test <num_buffers> <init_size> <max_size> <doublings> <iterations> [seed]\n");
+    exit(EXIT_FAILURE);
+  }
+
+  for ( int i = 0 ; i < argc ; i++ ) {
+    printf("%s ", argv[i]);
+  }
+  printf("\n");
+
+  if (argc == 7) {
+    srand(atoi(argv[6]));
+  } else {
+    srand(time(NULL));
+  }
+
+  struct TMemoryBuffer* buffers = calloc(num_buffers, sizeof(*buffers));
+  if (buffers == NULL) abort();
+
+  for ( int i = 0 ; i < num_buffers ; i++ ) {
+    buffers[i].size = max_size;
+  }
+
+  while (iterations --> 0) {
+    for ( int i = 0 ; i < doublings * num_buffers ; i++ ) {
+      struct TMemoryBuffer* buf = &buffers[rand() % num_buffers];
+      buf->size *= 2;
+      if (buf->size <= max_size) {
+        buf->ptr = realloc(buf->ptr, buf->size);
+      } else {
+        free(buf->ptr);
+        buf->size = init_size;
+        buf->ptr = malloc(buf->size);
+      }
+      if (buf->ptr == NULL) abort();
+    }
+  }
+
+  printf("Non-copied %d/%d (%.2f%%)\n", non_copies, copies + non_copies, 100.0 * non_copies / (copies + non_copies));
+  return 0;
+}
-- 
2.17.1