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treeClient.C File Reference

Detailed Description

Client program which creates and fills 2 histograms and a TTree.

Every 1000000 fills the histograms and TTree is send to the server which displays the histogram.

To run this demo do the following:

  • Open at least 2 windows
  • Start ROOT in the first windows
  • Execute in the first window: .x fastMergeServer.C
  • Execute in the other windows: root.exe -b -l -q .x treeClient.C (You can put it in the background if wanted). If you want to run the hserv.C on a different host, just change "localhost" in the TSocket ctor below to the desired hostname.
#include "TMessage.h"
#include "TBenchmark.h"
#include "TSocket.h"
#include "TH2.h"
#include "TTree.h"
#include "TMemFile.h"
#include "TRandom.h"
#include "TError.h"
void treeClient(Bool_t evol=kFALSE)
// Open connection to server
TSocket *sock = new TSocket("localhost", 9090);
if (!sock->IsValid()) {
Error("treeClient","Could not establish a connection with the server %s:%d.","localhost",9090);
// Wait till we get the start message
// server tells us who we are
Int_t status, version, kind;
sock->Recv(status, kind);
if (kind != 0 /* kStartConnection */)
Error("treeClient","Unexpected server message: kind=%d status=%d\n",kind,status);
delete sock;
sock->Recv(version, kind);
if (kind != 1 /* kStartConnection */)
Fatal("treeClient","Unexpected server message: kind=%d status=%d\n",kind,status);
} else {
Info("treeClient","Connected to fastMergeServer version %d\n",version);
int idx = status;
Float_t messlen = 0;
Float_t cmesslen = 0;
TMemFile *file = new TMemFile("mergedClient.root","RECREATE");
TH1 *hpx;
if (idx == 0) {
// Create the histogram
hpx = new TH1F("hpx","This is the px distribution",100,-4,4);
hpx->SetFillColor(48); // set nice fillcolor
} else {
hpx = new TH2F("hpxpy","py vs px",40,-4,4,40,-4,4);
Float_t px, py;
TTree *tree = new TTree("tree","tree");
// Fill histogram randomly
const int kUPDATE = 1000000;
for (int i = 0; i < 25000000; ) {
if (idx%2 == 0)
if (i && (i%kUPDATE) == 0) {
mess.Reset(kMESS_ANY); // re-use TMessage object
mess.WriteLong64(file->GetEND()); // 'mess << file->GetEND();' is broken in CINT for Long64_t
sock->Send(mess); // send message
messlen += mess.Length();
cmesslen += mess.CompLength();
file->ResetAfterMerge(nullptr); // This resets only the TTree objects.
sock->Send("Finished"); // tell server we are finished
if (cmesslen > 0)
printf("Average compression ratio: %g\n", messlen/cmesslen);
// Close the socket
bool Bool_t
Definition RtypesCore.h:63
int Int_t
Definition RtypesCore.h:45
float Float_t
Definition RtypesCore.h:57
constexpr Bool_t kFALSE
Definition RtypesCore.h:101
R__EXTERN TBenchmark * gBenchmark
Definition TBenchmark.h:59
void Info(const char *location, const char *msgfmt,...)
Use this function for informational messages.
Definition TError.cxx:218
void Error(const char *location, const char *msgfmt,...)
Use this function in case an error occurred.
Definition TError.cxx:185
void Fatal(const char *location, const char *msgfmt,...)
Use this function in case of a fatal error. It will abort the program.
Definition TError.cxx:244
R__EXTERN TRandom * gRandom
Definition TRandom.h:62
virtual void SetFillColor(Color_t fcolor)
Set the fill area color.
Definition TAttFill.h:37
virtual void Start(const char *name)
Starts Benchmark with the specified name.
virtual void Show(const char *name)
Stops Benchmark name and Prints results.
1-D histogram with a float per channel (see TH1 documentation)}
Definition TH1.h:577
TH1 is the base class of all histogram classes in ROOT.
Definition TH1.h:58
virtual void Reset(Option_t *option="")
Reset this histogram: contents, errors, etc.
Definition TH1.cxx:7098
virtual Int_t Fill(Double_t x)
Increment bin with abscissa X by 1.
Definition TH1.cxx:3345
2-D histogram with a float per channel (see TH1 documentation)}
Definition TH2.h:258
A TMemFile is like a normal TFile except that it reads and writes only from memory.
Definition TMemFile.h:19
static void EnableSchemaEvolutionForAll(Bool_t enable=kTRUE)
Static function enabling or disabling the automatic schema evolution.
Definition TMessage.cxx:116
virtual void SetSeed(ULong_t seed=0)
Set the random generator seed.
Definition TRandom.cxx:608
virtual void Rannor(Float_t &a, Float_t &b)
Return 2 numbers distributed following a gaussian with mean=0 and sigma=1.
Definition TRandom.cxx:500
virtual Int_t Recv(TMessage *&mess)
Receive a TMessage object.
Definition TSocket.cxx:818
virtual void Close(Option_t *opt="")
Close the socket.
Definition TSocket.cxx:389
virtual Bool_t IsValid() const
Definition TSocket.h:132
virtual Int_t Send(const TMessage &mess)
Send a TMessage object.
Definition TSocket.cxx:522
A TTree represents a columnar dataset.
Definition TTree.h:79
Definition file.py:1
Definition tree.py:1
Fons Rademakers, Philippe Canal

Definition in file treeClient.C.