Simplify COVER parameters

lib/dictBuilder/zdict.h

@@ -91,11 +91,9 @@ ZDICTLIB_API size_t ZDICT_trainFromBuffer_advanced(void* dictBuffer, size_t dict
     kMin and d are the only required parameters.
 */
 typedef struct {
-    unsigned d;                  /* dmer size : constraint: <= kMin : Should probably be in the range [6, 16]. */
-    unsigned kMin;               /* Minimum segment size : constraint: > 0 */
-    unsigned kStep;              /* Try kStep segment lengths uniformly distributed in the range [kMin, kMax] : 0 (default) only if kMax == 0 */
-    unsigned kMax;               /* Maximum segment size : 0 = kMin (default) : constraint : 0 or >= kMin */
-    unsigned smoothing;          /* Higher smoothing => larger segments are selected.  Only useful if kMax > kMin. */
+    unsigned k;                  /* Segment size : constraint: 0 < k : Reasonable range [16, 2048+] */
+    unsigned d;                  /* dmer size : constraint: 0 < d <= k : Reasonable range [6, 16] */
+    unsigned steps;              /* Number of steps : Only used for optimization : 0 means default (256) : Higher means more parameters checked */
 
     unsigned notificationLevel;  /* Write to stderr; 0 = none (default); 1 = errors; 2 = progression; 3 = details; 4 = debug; */
     unsigned dictID;             /* 0 means auto mode (32-bits random value); other : force dictID value */
@@ -125,11 +123,10 @@ ZDICTLIB_API size_t COVER_trainFromBuffer(void* dictBuffer, size_t dictBufferCap
     `*parameters` is filled with the best parameters found, and the dictionary
     constructed with those parameters is stored in `dictBuffer`.
 
-    All of the {d, kMin, kStep, kMax} are optional, and smoothing is ignored.
+    All of the parameters d, k, steps are optional.
     If d is non-zero then we don't check multiple values of d, otherwise we check d = {6, 8, 10, 12, 14, 16}.
-    If kStep is non-zero then it is used, otherwise we pick 8.
-    If kMin and kMax are non-zero, then they limit the search space for kMin and kMax,
-    otherwise we check kMin and kMax values in the range [32, 1024].
+    if steps is zero it defaults to its default value.
+    If k is non-zero then we don't check multiple values of k, otherwise we check steps values in [16, 2048].
 
     @return : size of dictionary stored into `dictBuffer` (<= `dictBufferCapacity`)
               or an error code, which can be tested with ZDICT_isError().