update README.md

Aux/README.md

@@ -2,6 +2,12 @@
 
 This stores auxillary programs, mainly focus on reading the *.fsu file, For example, the fsuReader.h is a *.fsu reader. 
 
+# Need to Make
+
+```sh
+make
+```
+
 # fsuReader.h
 
 This declare the FSUReader class. it can be included as a header in a custom cpp file, or it can be loaded on cern root CLI (command line interface). 
@@ -14,8 +20,38 @@ This declare the FSUReader class. it can be included as a header in a custom cpp
 ```
 The FSUReader can also read a fileList as a chain.
 
-Inside the FSUReader, there is a Data Class (from ClassData.h). This is why we need to set the data Buffer size for the reader. The data buffer is a circular buffer, typically 10 to 600 should be enough.
+Within the FSUReader, there exists a Data Class (defined in ClassData.h). This necessitates the specification of the data buffer size for the reader. The data buffer operates as a circular buffer, typically ranging from 10 to 600, which should be sufficient.
 
-There is a std::vector<Hit> in the FSUReader, in the ReadNextBlock(bool traceON = false, int verbose = 0, uShort saveData = 0), when saveData = 0, no data will be saved to the Hit vector, saveData = 1, no trace, and saveData = 2, with trace. Note that the Hit vector can be very memory demanding, especially with trace.
+The ScanNumBlock() method not only scans the number of blocks (or aggregations) but also tallies the number of hits.
 
-The ScanNumBlock() method scans number of block (or aggeragetion), and also extract the 
+The FSUReader includes a std::vector<Hit>, which is utilized in the ReadNextBlock(bool traceON = false, int verbose = 0, uShort saveData = 0) function. When saveData = 0, no data is stored in the Hit vector; saveData = 1 excludes trace data, while saveData = 2 includes it. It's worth noting that the Hit vector can be quite memory-intensive, particularly when trace data is included.
+
+The pivotal method for the event builder is the ReadBatch(unsigned int batchSize, bool verbose) function. This method reads a large number of Hits (with a size of batchSize). It effectively reads twice the specified batchSize: the first batch is stored as hitList_A, and the second as hitList_B. By comparing the timestamps of hitList_A and hitList_B, sorting if necessary, the method ensures that both hitLists are time-sorted. It then outputs hitList_A and internally stores hitList_B. Subsequent calls to this method replace hitList_A with hitList_B, retrieve a new batch to serve as the new hitList_B, repeat the sorting process, and output hitList_A.
+
+Occasionally, the earliest timestamp of hitList_B precedes that of hitList_A. In such cases, increasing the batchSize resolves the issue, albeit at the cost of higher memory usage. Typically, a batchSize of 1 million should suffice.
+
+With this approach, it is guaranteed that the output hitList_A is always time-sorted (given the batchSize is big enough), thereby simplifying the event building process.
+
+# EvenBuilder.cpp
+
+This defines the EventBuilder. The arguments are
+
+```sh
+./EventBuilder [timeWindow] [withTrace] [verbose] [batchSize] [inFile1]  [inFile2] .... 
+    timeWindow : in ns 
+     withTrace : 0 for no trace, 1 for trace 
+       verbose : > 0 for debug  
+     batchSize : the size of hit in a batch 
+    Output file name is contructed from inFile1 
+```
+
+as an example, 
+
+```sh
+/EventBuilder 0 0 0 1000000 '\ls -1 test_001*.fsu'
+
+```
+
+# SettingsExplorer.cpp
+
+This defines the Setting explorer, the explorer takes the setting *bin file as argument.