add a lorem ipsum generator

this generator replaces the statistical generator
for the general case when no statistic is requested.

Generated data features a compression level speed / ratio curve
which is more in line with expectation.

programs/benchzstd.c

@@ -32,12 +32,13 @@
 #include "benchfn.h"
 #include "../lib/common/mem.h"
 #ifndef ZSTD_STATIC_LINKING_ONLY
-#define ZSTD_STATIC_LINKING_ONLY
+# define ZSTD_STATIC_LINKING_ONLY
 #endif
 #include "../lib/zstd.h"
 #include "datagen.h"     /* RDG_genBuffer */
+#include "lorem.h"       /* LOREM_genBuffer */
 #ifndef XXH_INLINE_ALL
-#define XXH_INLINE_ALL
+# define XXH_INLINE_ALL
 #endif
 #include "../lib/common/xxhash.h"
 #include "benchzstd.h"
@@ -701,7 +702,8 @@ int BMK_syntheticTest(int cLevel, double compressibility,
                       const ZSTD_compressionParameters* compressionParams,
                       int displayLevel, const BMK_advancedParams_t* adv)
 {
-    char name[20] = {0};
+    char nameBuff[20] = {0};
+    const char* name = nameBuff;
     size_t const benchedSize = 10000000;
     void* srcBuffer;
     BMK_benchOutcome_t res;
@@ -719,10 +721,15 @@ int BMK_syntheticTest(int cLevel, double compressibility,
     }
 
     /* Fill input buffer */
-    RDG_genBuffer(srcBuffer, benchedSize, compressibility, 0.0, 0);
+    if (compressibility < 0.0) {
+        LOREM_genBuffer(srcBuffer, benchedSize, 0);
+        name = "Lorem ipsum";
+    } else {
+        RDG_genBuffer(srcBuffer, benchedSize, compressibility, 0.0, 0);
+        snprintf (nameBuff, sizeof(nameBuff), "Synthetic %2u%%", (unsigned)(compressibility*100));
+    }
 
     /* Bench */
-    snprintf (name, sizeof(name), "Synthetic %2u%%", (unsigned)(compressibility*100));
     res = BMK_benchCLevel(srcBuffer, benchedSize,
                     &benchedSize /* ? */, 1 /* ? */,
                     cLevel, compressionParams,

programs/benchzstd.h

@@ -126,11 +126,12 @@ int BMK_benchFilesAdvanced(
 
 /*! BMK_syntheticTest() -- called from zstdcli */
 /*  Generates a sample with datagen, using compressibility argument */
-/*  cLevel - compression level to benchmark, errors if invalid
- *  compressibility - determines compressibility of sample
- *  compressionParams - basic compression Parameters
- *  displayLevel - see benchFiles
- *  adv - see advanced_Params_t
+/* @cLevel - compression level to benchmark, errors if invalid
+ * @compressibility - determines compressibility of sample, range [0.0 - 1.0]
+ *        if @compressibility < 0.0, uses the lorem ipsum generator
+ * @compressionParams - basic compression Parameters
+ * @displayLevel - see benchFiles
+ * @adv - see advanced_Params_t
  * @return: 0 on success, !0 on error
  */
 int BMK_syntheticTest(int cLevel, double compressibility,

programs/lorem.c

@@ -0,0 +1,207 @@
+/*
+ * Copyright (c) Meta Platforms, Inc. and affiliates.
+ * All rights reserved.
+ *
+ * This source code is licensed under both the BSD-style license (found in the
+ * LICENSE file in the root directory of this source tree) and the GPLv2 (found
+ * in the COPYING file in the root directory of this source tree).
+ * You may select, at your option, one of the above-listed licenses.
+ */
+
+
+/* Implementation notes:
+ *
+ * This is a very simple lorem ipsum generator
+ * which features a static list of words
+ * and print them one after another randomly
+ * with a fake sentence / paragraph structure.
+ *
+ * The goal is to generate a printable text
+ * that can be used to fake a text compression scenario.
+ * The resulting compression / ratio curve of the lorem ipsum generator
+ * is more satisfying than the previous statistical generator,
+ * which was initially designed for entropy compression,
+ * and lacks a regularity more representative of text.
+ *
+ * The compression ratio achievable on the generated lorem ipsum
+ * is still a bit too good, presumably because the dictionary is too small.
+ * It would be possible to create some more complex scheme,
+ * notably by enlarging the dictionary with a word generator,
+ * and adding grammatical rules (composition) and syntax rules.
+ * But that's probably overkill for the intended goal.
+ */
+
+#include "lorem.h"
+#include <string.h>  /* memcpy */
+#include <limits.h>  /* INT_MAX */
+#include <assert.h>
+
+#define WORD_MAX_SIZE 20
+
+/* Define the word pool */
+static const char *words[] = {
+    "lorem",       "ipsum",      "dolor",      "sit",          "amet",
+    "consectetur", "adipiscing", "elit",       "sed",          "do",
+    "eiusmod",     "tempor",     "incididunt", "ut",           "labore",
+    "et",          "dolore",     "magna",      "aliqua",       "dis",
+    "lectus",      "vestibulum", "mattis",     "ullamcorper",  "velit",
+    "commodo",     "a",          "lacus",      "arcu",         "magnis",
+    "parturient",  "montes",     "nascetur",   "ridiculus",    "mus",
+    "mauris",      "nulla",      "malesuada",  "pellentesque", "eget",
+    "gravida",     "in",         "dictum",     "non",          "erat",
+    "nam",         "voluptat",   "maecenas",   "blandit",      "aliquam",
+    "etiam",       "enim",       "lobortis",   "scelerisque",  "fermentum",
+    "dui",         "faucibus",   "ornare",     "at",           "elementum",
+    "eu",          "facilisis",  "odio",       "morbi",        "quis",
+    "eros",        "donec",      "ac",         "orci",         "purus",
+    "turpis",      "cursus",     "leo",        "vel",          "porta"};
+
+/* simple distribution that favors small words :
+ * 1 letter : weight 3
+ * 2-3 letters : weight 2
+ * 4+ letters : weight 1
+ * This is expected to be a bit more difficult to compress */
+static const int distrib[] = {
+    0, 1, 2, 3, 3, 4, 5, 6, 7, 8,
+    8,9, 9, 10, 11, 12, 13, 13, 14, 15,
+    15, 16, 17, 18, 19, 19, 20, 21, 22, 23,
+    24, 25, 26, 26, 26, 27, 28, 29, 30, 31,
+    32, 33, 34, 34, 35, 36, 37, 38, 39, 40,
+    41, 41, 42, 43, 43, 44, 45, 45, 46, 47,
+    48, 49, 50, 51, 52, 53, 54, 55, 55, 56,
+    57, 58, 58, 59, 60, 60, 61, 62, 63, 64,
+    65, 66, 67, 67, 68, 69, 70, 71, 72, 72,
+    73, 73, 74 };
+static const unsigned distribCount = sizeof(distrib) / sizeof(distrib[0]);
+
+/* Note: this unit only works when invoked sequentially.
+ * No concurrent access is allowed */
+static char *g_ptr = NULL;
+static size_t g_nbChars = 0;
+static size_t g_maxChars = 10000000;
+static unsigned g_randRoot = 0;
+
+#define RDG_rotl32(x, r) ((x << r) | (x >> (32 - r)))
+static unsigned LOREM_rand(unsigned range) {
+  static const unsigned prime1 = 2654435761U;
+  static const unsigned prime2 = 2246822519U;
+  unsigned rand32 = g_randRoot;
+  rand32 *= prime1;
+  rand32 ^= prime2;
+  rand32 = RDG_rotl32(rand32, 13);
+  g_randRoot = rand32;
+  return (unsigned)(((unsigned long long)rand32 * range) >> 32);
+}
+
+static void writeLastCharacters(void) {
+  size_t lastChars = g_maxChars - g_nbChars;
+  assert(g_maxChars >= g_nbChars);
+  if (lastChars == 0)
+    return;
+  g_ptr[g_nbChars++] = '.';
+  if (lastChars > 2) {
+    memset(g_ptr + g_nbChars, ' ', lastChars - 2);
+  }
+  if (lastChars > 1) {
+    g_ptr[g_maxChars-1] = '\n';
+  }
+  g_nbChars = g_maxChars;
+}
+
+static void generateWord(const char *word, const char *separator, int upCase)
+{
+    size_t const len = strlen(word) + strlen(separator);
+    if (g_nbChars + len > g_maxChars) {
+        writeLastCharacters();
+        return;
+    }
+    memcpy(g_ptr + g_nbChars, word, strlen(word));
+    if (upCase) {
+        static const char toUp = 'A' - 'a';
+        g_ptr[g_nbChars] = (char)(g_ptr[g_nbChars] + toUp);
+    }
+    g_nbChars += strlen(word);
+    memcpy(g_ptr + g_nbChars, separator, strlen(separator));
+    g_nbChars += strlen(separator);
+}
+
+static int about(unsigned target) {
+  return (int)(LOREM_rand(target) + LOREM_rand(target) + 1);
+}
+
+/* Function to generate a random sentence */
+static void generateSentence(int nbWords) {
+  int commaPos = about(9);
+  int comma2 = commaPos + about(7);
+  int i;
+  for (i = 0; i < nbWords; i++) {
+    int const wordID = distrib[LOREM_rand(distribCount)];
+    const char *const word = words[wordID];
+    const char* sep = " ";
+    if (i == commaPos)
+      sep = ", ";
+    if (i == comma2)
+      sep = ", ";
+    if (i == nbWords - 1)
+      sep = ". ";
+    generateWord(word, sep, i==0);
+  }
+}
+
+static void generateParagraph(int nbSentences) {
+  int i;
+  for (i = 0; i < nbSentences; i++) {
+    int wordsPerSentence = about(8);
+    generateSentence(wordsPerSentence);
+  }
+  if (g_nbChars < g_maxChars) {
+    g_ptr[g_nbChars++] = '\n';
+  }
+  if (g_nbChars < g_maxChars) {
+    g_ptr[g_nbChars++] = '\n';
+  }
+}
+
+/* It's "common" for lorem ipsum generators to start with the same first
+ * pre-defined sentence */
+static void generateFirstSentence(void) {
+  int i;
+  for (i = 0; i < 18; i++) {
+    const char *word = words[i];
+    const char *separator = " ";
+    if (i == 4)
+      separator = ", ";
+    if (i == 7)
+      separator = ", ";
+    generateWord(word, separator, i==0);
+  }
+  generateWord(words[18], ". ", 0);
+}
+
+size_t LOREM_genBlock(void* buffer, size_t size,
+                      unsigned seed,
+                      int first, int fill)
+{
+  g_ptr = (char*)buffer;
+  assert(size < INT_MAX);
+  g_maxChars = size;
+  g_nbChars = 0;
+  g_randRoot = seed;
+  if (first) {
+    generateFirstSentence();
+  }
+  while (g_nbChars < g_maxChars) {
+    int sentencePerParagraph = about(7);
+    generateParagraph(sentencePerParagraph);
+    if (!fill)
+      break; /* only generate one paragraph in not-fill mode */
+  }
+  g_ptr = NULL;
+  return g_nbChars;
+}
+
+void LOREM_genBuffer(void* buffer, size_t size, unsigned seed)
+{
+  LOREM_genBlock(buffer, size, seed, 1, 1);
+}
+

programs/lorem.h

@@ -0,0 +1,32 @@
+/*
+ * Copyright (c) Meta Platforms, Inc. and affiliates.
+ * All rights reserved.
+ *
+ * This source code is licensed under both the BSD-style license (found in the
+ * LICENSE file in the root directory of this source tree) and the GPLv2 (found
+ * in the COPYING file in the root directory of this source tree).
+ * You may select, at your option, one of the above-listed licenses.
+ */
+
+/* lorem ipsum generator */
+
+#include <stddef.h>   /* size_t */
+
+/*
+ * LOREM_genBuffer():
+ * Generate @size bytes of compressible data using lorem ipsum generator
+ * into provided @buffer.
+ */
+void LOREM_genBuffer(void* buffer, size_t size, unsigned seed);
+
+/*
+ * LOREM_genBlock():
+ * Similar to LOREM_genBuffer, with additional controls :
+ * - @first : generate the first sentence
+ * - @fill : fill the entire @buffer,
+ *           if ==0: generate one paragraph at most.
+ * @return : nb of bytes generated into @buffer.
+ */
+size_t LOREM_genBlock(void* buffer, size_t size,
+                      unsigned seed,
+                      int first, int fill);

programs/zstdcli.c

@@ -856,7 +856,7 @@ int main(int argCount, const char* argv[])
     ZSTD_paramSwitch_e useRowMatchFinder = ZSTD_ps_auto;
     FIO_compressionType_t cType = FIO_zstdCompression;
     unsigned nbWorkers = 0;
-    double compressibility = 0.5;
+    double compressibility = -1.0;  /* lorem ipsum generator */
     unsigned bench_nbSeconds = 3;   /* would be better if this value was synchronized from bench */
     size_t blockSize = 0;