benchtests: Improve benchtests for strstr

Use same strategy as bench-strstr.c (93eebae516 and 80b2bfb535)
and use json_ctx for output to help standardize format across all
benchtests.
Reviewed-by: Arjun Shankar <arjun@redhat.com>

benchtests/bench-strcasestr.c

@@ -16,10 +16,36 @@
    License along with the GNU C Library; if not, see
    <https://www.gnu.org/licenses/>.  */
 
+#define MIN_PAGE_SIZE 131072
 #define TEST_MAIN
 #define TEST_NAME "strcasestr"
 #include "bench-string.h"
 
+#include "json-lib.h"
+
+static const char input[] =
+"This manual is written with the assumption that you are at least "
+"somewhat familiar with the C programming language and basic programming "
+"concepts.  Specifically, familiarity with ISO standard C (*note ISO "
+"C::), rather than “traditional” pre-ISO C dialects, is assumed.\n"
+
+"   The GNU C Library includes several “header files”, each of which "
+"provides definitions and declarations for a group of related facilities; "
+"this information is used by the C compiler when processing your program. "
+"For example, the header file ‘stdio.h’ declares facilities for "
+"performing input and output, and the header file ‘string.h’ declares "
+"string processing utilities.  The organization of this manual generally "
+"follows the same division as the header files.\n"
+
+"   If you are reading this manual for the first time, you should read "
+"all of the introductory material and skim the remaining chapters.  There "
+"are a _lot_ of functions in the GNU C Library and it’s not realistic to "
+"expect that you will be able to remember exactly _how_ to use each and "
+"every one of them.  It’s more important to become generally familiar "
+"with the kinds of facilities that the library provides, so that when you "
+"are writing your programs you can recognize _when_ to make use of "
+"library functions, and _where_ in this manual you can find more specific "
+"information about them.\n";
 
 #define STRCASESTR simple_strcasestr
 #define NO_ALIAS
@@ -32,123 +58,294 @@ typedef char *(*proto_t) (const char *, const char *);
 IMPL (simple_strcasestr, 0)
 IMPL (strcasestr, 1)
 
-
 static void
-do_one_test (impl_t *impl, const char *s1, const char *s2, char *exp_result)
+do_one_test (json_ctx_t *json_ctx, impl_t *impl, const char *s1,
+	     const char *s2, char *exp_result)
 {
-  size_t i, iters = INNER_LOOP_ITERS_SMALL;
+  size_t i, iters = INNER_LOOP_ITERS_SMALL / 8;
   timing_t start, stop, cur;
+  char *res;
 
   TIMING_NOW (start);
   for (i = 0; i < iters; ++i)
-    {
+    res = CALL (impl, s1, s2);
-      CALL (impl, s1, s2);
-    }
   TIMING_NOW (stop);
 
   TIMING_DIFF (cur, start, stop);
 
-  TIMING_PRINT_MEAN ((double) cur, (double) iters);
+  json_element_double (json_ctx, (double) cur / (double) iters);
+
+  if (res != exp_result)
+    {
+      error (0, 0, "Wrong result in function %s %s %s", impl->name,
+	     (res == NULL) ? "(null)" : res,
+	     (exp_result == NULL) ? "(null)" : exp_result);
+      ret = 1;
+    }
 }
 
-
 static void
-do_test (size_t align1, size_t align2, size_t len1, size_t len2,
+do_test (json_ctx_t *json_ctx, size_t align1, size_t align2, size_t len1,
-	 int fail)
+	 size_t len2, int fail)
 {
   char *s1 = (char *) (buf1 + align1);
   char *s2 = (char *) (buf2 + align2);
 
-  static const char d[] = "1234567890abcxyz";
+  size_t size = sizeof (input) - 1;
-#define dl (sizeof (d) - 1)
+  size_t pos = (len1 + len2) % size;
+
   char *ss2 = s2;
-  for (size_t l = len2; l > 0; l = l > dl ? l - dl : 0)
+  for (size_t l = len2; l > 0; l = l > size ? l - size : 0)
     {
-      size_t t = l > dl ? dl : l;
+      size_t t = l > size ? size : l;
-      ss2 = mempcpy (ss2, d, t);
+      if (pos + t <= size)
+	ss2 = mempcpy (ss2, input + pos, t);
+      else
+	{
+	  ss2 = mempcpy (ss2, input + pos, size - pos);
+	  ss2 = mempcpy (ss2, input, t - (size - pos));
+	}
     }
   s2[len2] = '\0';
 
-  if (fail)
+  char *ss1 = s1;
+  for (size_t l = len1; l > 0; l = l > size ? l - size : 0)
     {
-      char *ss1 = s1;
+      size_t t = l > size ? size : l;
-      for (size_t l = len1; l > 0; l = l > dl ? l - dl : 0)
+      memcpy (ss1, input, t);
-	{
+      ss1 += t;
-	  size_t t = l > dl ? dl : l;
-	  memcpy (ss1, d, t);
-	  ++ss1[len2 > 7 ? 7 : len2 - 1];
-	  ss1 += t;
-	}
-    }
-  else
-    {
-      memset (s1, '0', len1);
-      for (size_t i = 0; i < len2; ++i)
-	s1[len1 - len2 + i] = toupper (s2[i]);
     }
+
+  if (!fail)
+    memcpy (s1 + len1 - len2, s2, len2);
   s1[len1] = '\0';
 
-  printf ("Length %4zd/%zd, alignment %2zd/%2zd, %s:",
+  /* Remove any accidental matches except for the last if !fail.  */
-	  len1, len2, align1, align2, fail ? "fail" : "found");
+  for (ss1 = simple_strcasestr (s1, s2);
+       ss1 != NULL;
+       ss1 = simple_strcasestr (ss1 + 1, s2))
+    if (fail || ss1 != s1 + len1 - len2)
+      ++ss1[len2 / 2];
+
+  json_element_object_begin (json_ctx);
+  json_attr_uint (json_ctx, "len_haystack", len1);
+  json_attr_uint (json_ctx, "len_needle", len2);
+  json_attr_uint (json_ctx, "align_haystack", align1);
+  json_attr_uint (json_ctx, "align_needle", align2);
+  json_attr_uint (json_ctx, "fail", fail);
+
+  json_array_begin (json_ctx, "timings");
 
   FOR_EACH_IMPL (impl, 0)
-    do_one_test (impl, s1, s2, fail ? NULL : s1 + len1 - len2);
+    do_one_test (json_ctx, impl, s1, s2, fail ? NULL : s1 + len1 - len2);
 
-  putchar ('\n');
+  json_array_end (json_ctx);
+  json_element_object_end (json_ctx);
+
+}
+
+/* Test needles which exhibit worst-case performance for naive quadradic
+   implementations.  */
+
+static void
+test_hard_needle (json_ctx_t *json_ctx, size_t ne_len, size_t hs_len)
+{
+  char *ne = (char *) buf1;
+  char *hs = (char *) buf2;
+
+  /* Hard needle for strstr algorithm using skip table.  This results in many
+     memcmp calls comparing most of the needle.  */
+  {
+    memset (ne, 'a', ne_len);
+    ne[ne_len] = '\0';
+    ne[ne_len - 14] = 'b';
+
+    memset (hs, 'a', hs_len);
+    for (size_t i = ne_len; i <= hs_len; i += ne_len)
+      {
+	hs[i - 5] = 'b';
+	hs[i - 62] = 'b';
+      }
+
+    json_element_object_begin (json_ctx);
+    json_attr_uint (json_ctx, "len_haystack", hs_len);
+    json_attr_uint (json_ctx, "len_needle", ne_len);
+    json_attr_uint (json_ctx, "align_haystack", 0);
+    json_attr_uint (json_ctx, "align_needle", 0);
+    json_attr_uint (json_ctx, "fail", 1);
+    json_attr_string (json_ctx, "desc", "Difficult skiptable(0)");
+
+    json_array_begin (json_ctx, "timings");
+
+    FOR_EACH_IMPL (impl, 0)
+      do_one_test (json_ctx, impl, hs, ne, NULL);
+
+    json_array_end (json_ctx);
+    json_element_object_end (json_ctx);
+  }
+
+  /* 2nd hard needle for strstr algorithm using skip table.  This results in
+     many memcmp calls comparing most of the needle.  */
+  {
+    memset (ne, 'a', ne_len);
+    ne[ne_len] = '\0';
+    ne[ne_len - 6] = 'b';
+
+    memset (hs, 'a', hs_len);
+    for (size_t i = ne_len; i <= hs_len; i += ne_len)
+      {
+	hs[i - 5] = 'b';
+	hs[i - 6] = 'b';
+      }
+
+    json_element_object_begin (json_ctx);
+    json_attr_uint (json_ctx, "len_haystack", hs_len);
+    json_attr_uint (json_ctx, "len_needle", ne_len);
+    json_attr_uint (json_ctx, "align_haystack", 0);
+    json_attr_uint (json_ctx, "align_needle", 0);
+    json_attr_uint (json_ctx, "fail", 1);
+    json_attr_string (json_ctx, "desc", "Difficult skiptable(1)");
+
+    json_array_begin (json_ctx, "timings");
+
+    FOR_EACH_IMPL (impl, 0)
+      do_one_test (json_ctx, impl, hs, ne, NULL);
+
+    json_array_end (json_ctx);
+    json_element_object_end (json_ctx);
+  }
+
+  /* Hard needle for Two-way algorithm - the random input causes a large number
+     of branch mispredictions which significantly reduces performance on modern
+     micro architectures.  */
+  {
+    for (int i = 0; i < hs_len; i++)
+      hs[i] = (rand () & 255) > 155 ? 'a' : 'b';
+    hs[hs_len] = 0;
+
+    memset (ne, 'a', ne_len);
+    ne[ne_len - 2] = 'b';
+    ne[0] = 'b';
+    ne[ne_len] = 0;
+
+    json_element_object_begin (json_ctx);
+    json_attr_uint (json_ctx, "len_haystack", hs_len);
+    json_attr_uint (json_ctx, "len_needle", ne_len);
+    json_attr_uint (json_ctx, "align_haystack", 0);
+    json_attr_uint (json_ctx, "align_needle", 0);
+    json_attr_uint (json_ctx, "fail", 1);
+    json_attr_string (json_ctx, "desc", "Difficult 2-way");
+
+    json_array_begin (json_ctx, "timings");
+
+    FOR_EACH_IMPL (impl, 0)
+      do_one_test (json_ctx, impl, hs, ne, NULL);
+
+    json_array_end (json_ctx);
+    json_element_object_end (json_ctx);
+  }
+
+  /* Hard needle for standard algorithm testing first few characters of
+   * needle.  */
+  {
+    for (int i = 0; i < hs_len; i++)
+      hs[i] = (rand () & 255) >= 128 ? 'a' : 'b';
+    hs[hs_len] = 0;
+
+    for (int i = 0; i < ne_len; i++)
+      {
+	if (i % 3 == 0)
+	  ne[i] = 'a';
+	else if (i % 3 == 1)
+	  ne[i] = 'b';
+	else
+	  ne[i] = 'c';
+      }
+    ne[ne_len] = 0;
+
+    json_element_object_begin (json_ctx);
+    json_attr_uint (json_ctx, "len_haystack", hs_len);
+    json_attr_uint (json_ctx, "len_needle", ne_len);
+    json_attr_uint (json_ctx, "align_haystack", 0);
+    json_attr_uint (json_ctx, "align_needle", 0);
+    json_attr_uint (json_ctx, "fail", 1);
+    json_attr_string (json_ctx, "desc", "Difficult testing first 2");
+
+    json_array_begin (json_ctx, "timings");
+
+    FOR_EACH_IMPL (impl, 0)
+      do_one_test (json_ctx, impl, hs, ne, NULL);
+
+    json_array_end (json_ctx);
+    json_element_object_end (json_ctx);
+  }
 }
 
 static int
 test_main (void)
 {
+  json_ctx_t json_ctx;
   test_init ();
 
-  printf ("%23s", "");
+  json_init (&json_ctx, 0, stdout);
+
+  json_document_begin (&json_ctx);
+  json_attr_string (&json_ctx, "timing_type", TIMING_TYPE);
+
+  json_attr_object_begin (&json_ctx, "functions");
+  json_attr_object_begin (&json_ctx, TEST_NAME);
+  json_attr_string (&json_ctx, "bench-variant", "");
+
+  json_array_begin (&json_ctx, "ifuncs");
   FOR_EACH_IMPL (impl, 0)
-    printf ("\t%s", impl->name);
+    json_element_string (&json_ctx, impl->name);
-  putchar ('\n');
+  json_array_end (&json_ctx);
 
-  for (size_t klen = 2; klen < 32; ++klen)
+  json_array_begin (&json_ctx, "results");
-    for (size_t hlen = 2 * klen; hlen < 16 * klen; hlen += klen)
+
+  for (size_t hlen = 8; hlen <= 256;)
+    for (size_t klen = 1; klen <= 16; klen++)
       {
-	do_test (0, 0, hlen, klen, 0);
+	do_test (&json_ctx, 1, 3, hlen, klen, 0);
-	do_test (0, 0, hlen, klen, 1);
+	do_test (&json_ctx, 0, 9, hlen, klen, 1);
-	do_test (0, 3, hlen, klen, 0);
-	do_test (0, 3, hlen, klen, 1);
-	do_test (0, 9, hlen, klen, 0);
-	do_test (0, 9, hlen, klen, 1);
-	do_test (0, 15, hlen, klen, 0);
-	do_test (0, 15, hlen, klen, 1);
 
-	do_test (3, 0, hlen, klen, 0);
+	do_test (&json_ctx, 1, 3, hlen + 1, klen, 0);
-	do_test (3, 0, hlen, klen, 1);
+	do_test (&json_ctx, 0, 9, hlen + 1, klen, 1);
-	do_test (3, 3, hlen, klen, 0);
-	do_test (3, 3, hlen, klen, 1);
-	do_test (3, 9, hlen, klen, 0);
-	do_test (3, 9, hlen, klen, 1);
-	do_test (3, 15, hlen, klen, 0);
-	do_test (3, 15, hlen, klen, 1);
 
-	do_test (9, 0, hlen, klen, 0);
+	do_test (&json_ctx, getpagesize () - 15, 9, hlen, klen, 1);
-	do_test (9, 0, hlen, klen, 1);
+	if (hlen < 64)
-	do_test (9, 3, hlen, klen, 0);
+	  {
-	do_test (9, 3, hlen, klen, 1);
+	    hlen += 8;
-	do_test (9, 9, hlen, klen, 0);
+	  }
-	do_test (9, 9, hlen, klen, 1);
+	else
-	do_test (9, 15, hlen, klen, 0);
+	  {
-	do_test (9, 15, hlen, klen, 1);
+	    hlen += 32;
-
+	  }
-	do_test (15, 0, hlen, klen, 0);
-	do_test (15, 0, hlen, klen, 1);
-	do_test (15, 3, hlen, klen, 0);
-	do_test (15, 3, hlen, klen, 1);
-	do_test (15, 9, hlen, klen, 0);
-	do_test (15, 9, hlen, klen, 1);
-	do_test (15, 15, hlen, klen, 0);
-	do_test (15, 15, hlen, klen, 1);
       }
 
-  do_test (0, 0, page_size - 1, 16, 0);
+  for (size_t hlen = 256; hlen <= 65536; hlen *= 2)
-  do_test (0, 0, page_size - 1, 16, 1);
+    for (size_t klen = 4; klen <= 256; klen *= 2)
+      {
+	do_test (&json_ctx, 1, 11, hlen, klen, 0);
+	do_test (&json_ctx, 14, 5, hlen, klen, 1);
+
+    do_test (&json_ctx, 1, 11, hlen + 1, klen + 1, 0);
+    do_test (&json_ctx, 14, 5, hlen + 1, klen + 1, 1);
+
+	do_test (&json_ctx, 1, 11, hlen + 1, klen, 0);
+	do_test (&json_ctx, 14, 5, hlen + 1, klen, 1);
+
+	do_test (&json_ctx, getpagesize () - 15, 5, hlen + 1, klen, 1);
+      }
+
+  test_hard_needle (&json_ctx, 64, 65536);
+  test_hard_needle (&json_ctx, 256, 65536);
+  test_hard_needle (&json_ctx, 1024, 65536);
+
+  json_array_end (&json_ctx);
+  json_attr_object_end (&json_ctx);
+  json_attr_object_end (&json_ctx);
+  json_document_end (&json_ctx);
 
   return ret;
 }