[cover] Make optimization faster

diff --git a/lib/dictBuilder/cover.c b/lib/dictBuilder/cover.c
index 4235f112b7fb3a20807ad62c84fc8f741cf05276..0e156bd5852e58aebe88f29c8d02fa919a99823e 100644 (file)
--- a/lib/dictBuilder/cover.c
+++ b/lib/dictBuilder/cover.c
@@ -939,8 +939,8 @@ ZDICTLIB_API size_t COVER_optimizeTrainFromBuffer(void *dictBuffer,
   /* constants */
   const unsigned nbThreads = parameters->nbThreads;
   const unsigned kMinD = parameters->d == 0 ? 6 : parameters->d;
-  const unsigned kMaxD = parameters->d == 0 ? 16 : parameters->d;
-  const unsigned kMinK = parameters->k == 0 ? kMaxD : parameters->k;
+  const unsigned kMaxD = parameters->d == 0 ? 8 : parameters->d;
+  const unsigned kMinK = parameters->k == 0 ? 40 + kMaxD : parameters->k;
   const unsigned kMaxK = parameters->k == 0 ? 2048 : parameters->k;
   const unsigned kSteps = parameters->steps == 0 ? 32 : parameters->steps;
   const unsigned kStepSize = MAX((kMaxK - kMinK) / kSteps, 1);

diff --git a/programs/zstd.1 b/programs/zstd.1
index 5bd966a841df2654986622c789a299f560fcf268..648c3365cc74b8e4a5bc37c83c7bd16bc634e6c9 100644 (file)
--- a/programs/zstd.1
+++ b/programs/zstd.1
@@ -195,13 +195,13 @@ Example: \fB\-\-train \-\-cover=k=64,d=8 FILEs\fR\.
 .
 .TP
 \fB\-\-optimize\-cover[=steps=#,k=#,d=#]\fR
-If \fIsteps\fR is not specified, the default value of 32 is used\. If \fIk\fR is not specified, the \fIk\fR values in [16, 2048] are checked for each value of \fId\fR\. If \fId\fR is not specified, the values checked are [6, 8, \.\.\., 16]\.
+If \fIsteps\fR is not specified, the default value of 32 is used\. If \fIk\fR is not specified, the \fIk\fR values in [48, 2048] are checked for each value of \fId\fR\. If \fId\fR is not specified, the values checked are [6, 8]\.
 .
 .IP
 Runs the cover dictionary builder for each parameter set and saves the optimal parameters and dictionary\. Prints optimal parameters and writes optimal dictionary into output file\. Supports multithreading if \fBzstd\fR is compiled with threading support\.
 .
 .IP
-The parameter \fIk\fR is more sensitive than \fId\fR, and is faster to optimize over\. Suggested use is to run with a \fIsteps\fR <= 32 with neither \fIk\fR nor \fId\fR set\. Once it completes, use the value of \fId\fR it selects with a higher \fIsteps\fR (in the range [256, 1024])\.
+The parameter \fIk\fR is more sensitive than \fId\fR, and is faster to optimize over\.
 .
 .IP
 Examples :
@@ -210,7 +210,7 @@ Examples :
 \fBzstd \-\-train \-\-optimize\-cover FILEs\fR
 .
 .IP
-\fBzstd \-\-train \-\-optimize\-cover=d=d,steps=512 FILEs\fR
+\fBzstd \-\-train \-\-optimize\-cover=d=8,steps=512 FILEs\fR
 .
 .SH "BENCHMARK"
 .

diff --git a/programs/zstd.1.md b/programs/zstd.1.md
index 0919da70265f6fdeec098aa37a02e907b6327999..ea346cfb7fbf5a3f8e9eaff5d7fa843ab579e5d4 100644 (file)
--- a/programs/zstd.1.md
+++ b/programs/zstd.1.md
@@ -194,9 +194,9 @@ Typical gains range from 10% (at 64KB) to x5 better (at <1KB).
 
 * `--optimize-cover[=steps=#,k=#,d=#]`:
     If _steps_ is not specified, the default value of 32 is used.
-    If _k_ is not specified, the _k_ values in [16, 2048] are checked for each
+    If _k_ is not specified, the _k_ values in [48, 2048] are checked for each
     value of _d_.
-    If _d_ is not specified, the values checked are [6, 8, ..., 16].
+    If _d_ is not specified, the values checked are [6, 8].
 
     Runs the cover dictionary builder for each parameter set
     and saves the optimal parameters and dictionary.
@@ -204,15 +204,12 @@ Typical gains range from 10% (at 64KB) to x5 better (at <1KB).
     Supports multithreading if `zstd` is compiled with threading support.
 
     The parameter _k_ is more sensitive than _d_, and is faster to optimize over.
-    Suggested use is to run with a _steps_ <= 32 with neither _k_ nor _d_ set.
-    Once it completes, use the value of _d_ it selects with a higher _steps_
-    (in the range [256, 1024]).
 
     Examples :
 
     `zstd --train --optimize-cover FILEs`
 
-    `zstd --train --optimize-cover=d=d,steps=512 FILEs`
+    `zstd --train --optimize-cover=d=8,steps=512 FILEs`
 
 
 BENCHMARK