Merge pull request facebook#2538 from senhuang42/monotonicity_test

Add memory monotonicity test over srcSize

Author: senhuang42

lib/compress/zstd_compress.c

@@ -1390,15 +1390,23 @@ size_t ZSTD_estimateCCtxSize_usingCParams(ZSTD_compressionParameters cParams)
 
 static size_t ZSTD_estimateCCtxSize_internal(int compressionLevel)
 {
-    ZSTD_compressionParameters const cParams = ZSTD_getCParams_internal(compressionLevel, ZSTD_CONTENTSIZE_UNKNOWN, 0, ZSTD_cpm_noAttachDict);
-    return ZSTD_estimateCCtxSize_usingCParams(cParams);
+    int tier = 0;
+    size_t largestSize = 0;
+    static const unsigned long long srcSizeTiers[4] = {16 KB, 128 KB, 256 KB, ZSTD_CONTENTSIZE_UNKNOWN};
+    for (; tier < 4; ++tier) {
+        /* Choose the set of cParams for a given level across all srcSizes that give the largest cctxSize */
+        ZSTD_compressionParameters const cParams = ZSTD_getCParams_internal(compressionLevel, srcSizeTiers[tier], 0, ZSTD_cpm_noAttachDict);
+        largestSize = MAX(ZSTD_estimateCCtxSize_usingCParams(cParams), largestSize);
+    }
+    return largestSize;
 }
 
 size_t ZSTD_estimateCCtxSize(int compressionLevel)
 {
     int level;
     size_t memBudget = 0;
     for (level=MIN(compressionLevel, 1); level<=compressionLevel; level++) {
+        /* Ensure monotonically increasing memory usage as compression level increases */
         size_t const newMB = ZSTD_estimateCCtxSize_internal(level);
         if (newMB > memBudget) memBudget = newMB;
     }

tests/fuzzer.c

@@ -3181,6 +3181,48 @@ static int basicUnitTests(U32 const seed, double compressibility)
     }
     DISPLAYLEVEL(3, "OK \n");
 
+    DISPLAYLEVEL(3, "test%3i : check compression mem usage monotonicity over levels for estimateCCtxSize() : ", testNb++);
+    {
+        int level = 1;
+        size_t prevSize = 0;
+        for (; level < ZSTD_maxCLevel(); ++level) {
+            size_t const currSize = ZSTD_estimateCCtxSize(level);
+            if (prevSize > currSize) {
+                DISPLAYLEVEL(3, "Error! previous cctx size: %zu at level: %d is larger than current cctx size: %zu at level: %d",
+                             prevSize, level-1, currSize, level);
+                goto _output_error;
+            }
+            prevSize = currSize;
+        }
+    }
+    DISPLAYLEVEL(3, "OK \n");
+
+    DISPLAYLEVEL(3, "test%3i : check estimateCCtxSize() always larger or equal to ZSTD_estimateCCtxSize_usingCParams() : ", testNb++);
+    {
+        size_t const kSizeIncrement = 2 KB;
+        int level = -3;
+
+        for (; level <= ZSTD_maxCLevel(); ++level) {
+            size_t dictSize = 0;
+            for (; dictSize <= 256 KB; dictSize += 8 * kSizeIncrement) {
+                size_t srcSize = 2 KB;
+                for (; srcSize < 300 KB; srcSize += kSizeIncrement) {
+                    ZSTD_compressionParameters const cParams = ZSTD_getCParams(level, srcSize, dictSize);
+                    size_t const cctxSizeUsingCParams = ZSTD_estimateCCtxSize_usingCParams(cParams);
+                    size_t const cctxSizeUsingLevel = ZSTD_estimateCCtxSize(level);
+                    if (cctxSizeUsingLevel < cctxSizeUsingCParams
+                     || ZSTD_isError(cctxSizeUsingCParams)
+                     || ZSTD_isError(cctxSizeUsingLevel)) {
+                        DISPLAYLEVEL(3, "error! l: %d dict: %zu srcSize: %zu cctx size cpar: %zu, cctx size level: %zu\n",
+                                     level, dictSize, srcSize, cctxSizeUsingCParams, cctxSizeUsingLevel);
+                        goto _output_error;
+                    }
+                }
+            }
+        }
+    }
+    DISPLAYLEVEL(3, "OK \n");
+
 #endif
 
 _end: