cling – the new c++ interpreter for root 6 cern, ph-sft & fermilab v. vassilev, p. canal, a....
TRANSCRIPT
Cling – The New C++ Cling – The New C++ Interpreter for ROOT 6Interpreter for ROOT 6
CERN, PH-SFT & FermiLabCERN, PH-SFT & FermiLab
V. Vassilev, P. Canal, A. Naumann, P. RussoV. Vassilev, P. Canal, A. Naumann, P. Russo
vvassilev / CHEP 2012.05.21 2
Role of C++ Interpreter in ROOT
Load/Store C++ objects Runtime Dynamism
TFile::Open(“http://...”)
gDirectory->Get(“hist”)
python runReco.py
Fast Prototyping
ROOT
CINT
Reflection
TPluginManager
IO
...
PyR
OO
T
Type Info
TClass
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Role of C++ Interpreter in ROOT
ROOT uses the interpreter much more than one would expect:
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Cling Is Better Than CINT
Full C++ support STL + templates Path to C++11
Correctness Better type information and representations Always compile in memory Much less code to maintain
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Cling's Dual Personality
An interpreter – looks like an interpreter and behaves like an interpreterCling follows the read-evaluate-print-loop (repl) concept.
More than interpreter – built on top of compiler libraries (Clang and LLVM)Contains interpreter parts and compiler parts. More of an interactive compiler or an interactive compiler interface for clang.
No need to compile Cling/ROOT with Clang/LLVM
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Cling Uses Clang & LLVM
LLVM and Clang “The LLVM Project is a collection of modular and reusable compiler and
toolchain technologies...”
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Cling's Codebase
* No testsuites included.Credits: generated using David A. Wheeler's 'SLOCCount'
Other ROOT – 1400K SLOC*
CINT+Reflex – 230K SLOC*
Cling – 7K SLOC*
ROOT
CINT+Reflex
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Other ROOT – 1400K SLOC*
CINT+Reflex – 230K SLOC*
Cling – 7K SLOC*
externals:
LLVM + Clang – 800K SLOC*
Cling's Codebase
* No testsuites included.Credits: generated using David A. Wheeler's 'SLOCCount'
ROOT
Cling
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Challenges
Incompatible concepts like compilation and interpretationMany tasks that are trivial for an interpreter become a nightmare for a compiler.
Make C++ usable at the promptIncorporate the experience we have with CINT. First step: adopt the successful usability extensions from CINT.
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Cling in a NutshellCling in a Nutshell
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Extending C++ Language
[cling]$ sin(12);void wrapper() { sin(12);}
[cling]$ [cling]$
int i = 12;sin(i);
void wrapper1() { int i = 12;}
void wrapper2() { sin(i);}
?We want to be able to
run statements
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[cling]$ [cling]$
int i = 12; printf("%d\n",i);printf("%f\n",sin(i));
Extending C++ Language
Wrap the input Look for declarations Extract the declarations one level up, as global
declarations
void wrapper1() { int i = 12; printf("%d\n",i);}
void wrapper2() { printf("%f\n", sin(i));}
int i = 12;
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Streaming Execution Results
[cling]$ [cling]$
int i = 12(int) 12sin(i)(double const) -5.365729e-01
No semicolon (;)No semicolon (;)
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Error Recovery
Filled input-by-input Incorrect inputs must be discarded as a whole
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Work in progress: Code Unloading
[cling]$ [cling]$ [cling]$ [cling]$ [cling]$ [cling]$ [cling]$ [cling]$ [cling]$
.L Calculator.hCalculator calc;calc.Add(3, 1)(int) 2 //WTF!?*.U Calculator.h.L Calculator.hCalculator calc;calc.Add(3, 1)(int) 4 //
// Calculator.hclass Calculator { int Add(int a, int b) { return a + b; }...};
// Calculator.hclass Calculator { int Add(int a, int b) { return a - b; }...};
* What's That Function
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Late Binding
{ TFile* F = 0; if (is_day_of_month_even()) F = TFile::Open("even.root"); else F = TFile::Open("odd.root"); hist->Draw();}hist->Draw();
Defined in the root file
The root file is gone. Issue an error.
Opens a dynamic scope. It tells the compiler that cling will take over the resolution of possible unknown identifiers
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Late Binding
{ TFile* F = 0; if (is_day_of_month_even()) F = TFile::Open("even.root"); else F = TFile::Open("odd.root"); gCling->EvaluateT<void>("hist->Draw()", ...);}
hist->Draw(); Tell the compiler the identifier will be resolved at runtime
Wrap it into valid C++ code
Partially recompile at runtime
Automatically transformed into valid
C++ code
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Challenges
Error recoveryEven though the user has typed wrong input at the prompt cling must survive, i.e issue an error and continue to work.
Initialization of global variablesCling depends on global variables, which need to be initialized. However, the global variables continue to be added (potentially) with every input line.
Late bindingCling needs to provide a way for symbols unavailable at compile-time a second chance to be provided at runtime.
Value printerThe interactive mode obeys the repl concept and there should be way of easy print value and type of expression in a user-extensible way.
Running statementsCINT-specific C++ extension improving the user interaction with the interpreter from the terminal.
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Cling In The World
Announced in July 2011 as working C++ interpreter
Cling and OpenGLhttp://www.youtube.com/watch?v=eoIuqLNvzFs
Cling and QThttp://www.youtube.com/watch?v=BrjV1ZgYbbA
MATLAB to C++ translator Regular bug reports from outside HEP
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Cling In ROOTCling In ROOT
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Dictionaries
Describe compiled codeIncarnation of the type information and reflection in ROOT. The only way of crossing the border between interpretation and compilation.
CINT and Reflex dictionaries: Double the size of the libraries Multiple copies of the dictionary data in the memory Incompatible reflection formats Do not cover 100% of C++ CINT
Reflection
TPluginManager
IO
...
PyR
OO
T
Type Info
TClass
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CINT Dictionary Use
Dictionary.(h|cxx)
ClassDef
Call Stubs
Reflection Info
TClass
Source of ROOT's class description
Member functions injected by the
ClassDef macro
Target-independent, normalized signatures used to call compiled
functions.Teaches CINT what a
class contains
Dictionary Size (SLOC)
6%
10%
61%
23%
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LLVM Just-In-Time Compiler
Cling
Clang
LLVM Bit Code
LLVM JIT
Machine Code (x86, Alpha, ...)
Compiles lazily just before the function is called
Has full knowledge about the target architecture
Much faster than interpreting the LLVM Bit Code
Compiled libs(.so)
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Cling + ROOT = ROOT 6
ROOT 6 in NovemberSee plenary by Fons on Wednesday
Windows support to arrive after 6.00Work in progress in clang
“genreflex”-compatible dictionary generator after 6.00
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Reduce size of dictionaries Mid term: Call Stubs & Reflection Info goes away! Long term: No dictionaries at all
Compiled TFormula
ROOT 6.x
Dictionary.(h|cxx)
ClassDef
Call Stubs
Reflection Info
TClass
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Additional Features
World class performance and optimizations OpenCL C Objective C[++] ...
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In ActionIn Action
Come and see at our booth!Come and see at our booth!
C N GC N G
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Thank you!Thank you!
Fons's plenary on Wednesday Google Tech Talk LLVM Euro Dev Meeting 2011
http://www.llvm.org/devmtg/2011-09-16/EuroLLVM2011-ImplementingDynamicScopesInCling.pdf
LLVM Dev Meeting 2011http://www.llvm.org/devmtg/2010-11/Naumann-Cling.pdf
http://www.llvm.org/devmtg/2010-11/videos/Naumann_Cling-desktop.mp4
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Backup slidesBackup slides
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Pre-Compiled Headers/Modules
Carefully crafted data structures designed to improve translator's performance:
Reduce lexical, syntax and semantic analysis
Loaded “lazily” on demand
http
://c
lang
.llvm
.org
/do
cs/P
CH
Inte
rnal
s.ht
ml
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Pre-Compiled Headers/Modules
Design advantages: Loading is significantly faster than re-parsing Minimize the cost of reading Read times don't depend on size Cost of generating isn't large
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PCH vs PCM
PCH PCM
And thus PCM much more flexible
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Expressive Diagnostics
Column numbers and caret diagnosticsCaretDiagnostics.C:4:13: warning: '.*' specified field precision is missing a matching 'int' argumentprintf("%.*d"); ~~^~
Range highlightingRangeHighlight.C:14:39: error: invalid operands to binary expression ('int' and 'A')return y + func(y ? ((SomeA.X + 40) + SomeA) / 42 + SomeA.X : SomeA.X); ~~~~~~~~~~~~ ^ ~~~~~~~
Fix-it hintsFixItHints.C:7:27: warning: use of GNU old-style field designator extensionstruct point origin = { x: 0.0, y: 0.0 }; ^~ .x =
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LLVM Compiler Toolchain
LLVM Core “The LLVM Project is a collection of modular and reusable compiler and toolchain technologies...”
More than 120 active contributorsApple, ARM, Google, Qualcomm, QuIC, NVidia, AMD and more
~250 commits/week Clang
“The goal of the Clang project is to create a new C, C++, Objective C and Objective C++ front-end for the LLVM compiler.“
More than 100 active contributorsApple, ARM, AMD and more
~150 commits/week* Stats from last year until 14.10.2011
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Correctness
http://root.cern.ch/drupal/content/requested-cling-features