Changeset dcfc4b35 for doc/proposals/concurrency/text/cforall.tex
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- Oct 3, 2017, 3:09:12 PM (7 years ago)
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doc/proposals/concurrency/text/cforall.tex (modified) (3 diffs)
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doc/proposals/concurrency/text/cforall.tex
re1ff775 rdcfc4b35 5 5 % ====================================================================== 6 6 7 As mentionned in the introduction, the document presents the design for the concurrency features in \CFA. Since it is a new language here is a quick review of the languagespecifically tailored to the features needed to support concurrency.7 This thesis presents the design for a set of concurrency features in \CFA. Since it is a new dialect of C, the following is a quick introduction to the language, specifically tailored to the features needed to support concurrency. 8 8 9 \CFA is a extension of ISO C and therefore supports much of the same paradigms as C. It is a non-object oriented system level language, meaning it has very most of the major abstractions have either no runtime cost or can be opt-out easily. Like C, the basics of \CFA revolve around structures and routines, which are thin abstractions over assembly. The vast majority of the code produced by a \CFA compiler respects memory-layouts and calling-conventions laid out by C. However, while \CFA is not an object-oriented language according to a strict definition. It does have some notion of objects, most importantly construction and destruction of objects. Most of the following pieces of code can be found as is on the \CFA website :\cite{www-cfa}9 \CFA is a extension of ISO-C and therefore supports all of the same paradigms as C. It is a non-object oriented system language, meaning most of the major abstractions have either no runtime overhead or can be opt-out easily. Like C, the basics of \CFA revolve around structures and routines, which are thin abstractions over machine code. The vast majority of the code produced by the \CFA translator respects memory-layouts and calling-conventions laid out by C. Interestingly, while \CFA is not an object-oriented language, lacking the concept of a received (e.g.: this), it does have some notion of objects\footnote{C defines the term objects as : [Where to I get the C11 reference manual?]}, most importantly construction and destruction of objects. Most of the following pieces of code can be found on the \CFA website \cite{www-cfa} 10 10 11 11 \section{References} 12 12 13 Like \CC, \CFA introduces references as an alternative to pointers. In regards to concurrency, the semantics difference between pointers and references are n't particularly relevant but since this document uses mostly references here is a quick overview of the semantics :13 Like \CC, \CFA introduces references as an alternative to pointers. In regards to concurrency, the semantics difference between pointers and references are not particularly relevant but since this document uses mostly references here is a quick overview of the semantics : 14 14 \begin{cfacode} 15 15 int x, *p1 = &x, **p2 = &p1, ***p3 = &p2, 16 16 &r1 = x, &&r2 = r1, &&&r3 = r2; 17 ***p3 = 3; // change x 18 r3 = 3; // change x, ***r3 19 **p3 = ...; // change p1 20 &r3 = ...; // change r1, (&*)**r3 21 *p3 = ...; // change p2 22 &&r3 = ...; // change r2, (&(&*)*)*r3 23 &&&r3 = p3; // change r3 to p3, (&(&(&*)*)*)r3 24 int y, z, & ar[3] = { x, y, z }; // initialize array of references 25 &ar[1] = &z; // change reference array element 26 typeof( ar[1] ) p; // is int, i.e., the type of referenced object 27 typeof( &ar[1] ) q; // is int &, i.e., the type of reference 28 sizeof( ar[1] ) == sizeof( int ); // is true, i.e., the size of referenced object 29 sizeof( &ar[1] ) == sizeof( int *); // is true, i.e., the size of a reference 17 ***p3 = 3; //change x 18 r3 = 3; //change x, ***r3 19 **p3 = ...; //change p1 20 *p3 = ...; //change p2 21 int y, z, & ar[3] = {x, y, z}; //initialize array of references 22 typeof( ar[1]) p; //is int, i.e., the type of referenced object 23 typeof(&ar[1]) q; //is int &, i.e., the type of reference 24 sizeof( ar[1]) == sizeof(int); //is true, i.e., the size of referenced object 25 sizeof(&ar[1]) == sizeof(int *); //is true, i.e., the size of a reference 30 26 \end{cfacode} 31 27 The important thing to take away from this code snippet is that references offer a handle to an object much like pointers but which is automatically derefferenced when convinient. … … 33 29 \section{Overloading} 34 30 35 Another important feature \CFA has in common with \CC is function overloading :31 Another important feature of \CFA is function overloading as in Java and \CC, where routine with the same name are selected based on the numbers and type of the arguments. As well, \CFA uses the return type as part of the selection criteria, as in Ada\cite{Ada}. For routines with multiple parameters and returns, the selection is complex. 36 32 \begin{cfacode} 37 // 38 void f( void ); //(1)39 void f( char ); //(2)40 void f( int, double ); //(3)41 f(); // 42 f( 'a' ); //select (2)43 f( 3, 5.2 ); //select (3)33 //selection based on type and number of parameters 34 void f(void); //(1) 35 void f(char); //(2) 36 void f(int, double); //(3) 37 f(); //select (1) 38 f('a'); //select (2) 39 f(3, 5.2); //select (3) 44 40 45 // selection based on type and number of returns 46 char f( int ); // (1) 47 double f( int ); // (2) 48 [ int, double ] f( int ); // (3) 49 char c = f( 3 ); // select (1) 50 double d = f( 4 ); // select (2) 51 [ int, double ] t = f( 5 ); // select (3) 41 //selection based on type and number of returns 42 char f(int); //(1) 43 double f(int); //(2) 44 char c = f(3); //select (1) 45 double d = f(4); //select (2) 52 46 \end{cfacode} 53 This feature is particularly important for concurrency since the runtime system relies on creating different types do represent concurrency objects. Therefore, overloading is necessary to prevent the need for long prefixes and other naming conventions that prevent clashes. As seen in chapter \ref{basics}, the main is an example of routine that benefits from overloading when concurrency in introduced.47 This feature is particularly important for concurrency since the runtime system relies on creating different types to represent concurrency objects. Therefore, overloading is necessary to prevent the need for long prefixes and other naming conventions that prevent name clashes. As seen in chapter \ref{basics}, routines main is an example that benefits from overloading. 54 48 55 49 \section{Operators} 56 50 Overloading also extends to operators. The syntax for denoting operator-overloading is to name a routine with the symbol of the operator and question marks where the arguments of the operation would be, like so : 57 51 \begin{cfacode} 58 int ++? ( int op ); //unary prefix increment59 int ?++ ( int op ); //unary postfix increment60 int ?+? ( int op1, int op2 ); //binary plus61 int ?<=?( int op1, int op2 ); //binary less than62 int ?=? ( int & op1, int op2 ); //binary assignment63 int ?+=?( int & op1, int op2 ); //binary plus-assignment52 int ++? (int op); //unary prefix increment 53 int ?++ (int op); //unary postfix increment 54 int ?+? (int op1, int op2); //binary plus 55 int ?<=?(int op1, int op2); //binary less than 56 int ?=? (int & op1, int op2); //binary assignment 57 int ?+=?(int & op1, int op2); //binary plus-assignment 64 58 65 struct S { int i, j;};66 S ?+?( S op1, S op2 ) { //add two structures67 return (S){ op1.i + op2.i, op1.j + op2.j};59 struct S {int i, j;}; 60 S ?+?(S op1, S op2) { //add two structures 61 return (S){op1.i + op2.i, op1.j + op2.j}; 68 62 } 69 S s1 = { 1, 2 }, s2 = { 2, 3}, s3;70 s3 = s1 + s2; // compute sum: s3 == { 2, 5}63 S s1 = {1, 2}, s2 = {2, 3}, s3; 64 s3 = s1 + s2; //compute sum: s3 == {2, 5} 71 65 \end{cfacode} 72 73 Since concurrency does not use operator overloading, this feature is more important as an introduction for the syntax of constructors. 66 While concurrency does not use operator overloading directly, this feature is more important as an introduction for the syntax of constructors. 74 67 75 68 \section{Constructors/Destructors} 76 Object life time is often a challenge in concurrency. \CFA uses the approach of giving concurrent meaning to object life time as a mean of synchronization and/or mutual exclusion. Since \CFA relies heavily on the life time of objects, Constructors \& Destructors are a the core of the featuresrequired for concurrency and parallelism. \CFA uses the following syntax for constructors and destructors :69 Object life-time is often a challenge in concurrency. \CFA uses the approach of giving concurrent meaning to object life-time as a mean of synchronization and/or mutual exclusion. Since \CFA relies heavily on the life time of objects, constructors and destructors are a core feature required for concurrency and parallelism. \CFA uses the following syntax for constructors and destructors : 77 70 \begin{cfacode} 78 71 struct S { … … 80 73 int * ia; 81 74 }; 82 void ?{}( S & s, int asize ) with s { //constructor operator83 s ize = asize; //initialize fields84 ia = calloc( size, sizeof( S ));75 void ?{}(S & s, int asize) { //constructor operator 76 s.size = asize; //initialize fields 77 s.ia = calloc(size, sizeof(S)); 85 78 } 86 void ^?{}( S & s ) with s { //destructor operator87 free( ia ); //de-initialization fields79 void ^?{}(S & s) { //destructor operator 80 free(ia); //de-initialization fields 88 81 } 89 82 int main() { 90 S x = { 10 }, y = { 100 }; // implict calls: ?{}( x, 10 ), ?{}( y, 100)91 ... //use x and y92 ^x{}; ^y{}; //explicit calls to de-initialize93 x{ 20 }; y{ 200 }; //explicit calls to reinitialize94 ... //reuse x and y95 } // implict calls: ^?{}( y ), ^?{}( x)83 S x = {10}, y = {100}; //implict calls: ?{}(x, 10), ?{}(y, 100) 84 ... //use x and y 85 ^x{}; ^y{}; //explicit calls to de-initialize 86 x{20}; y{200}; //explicit calls to reinitialize 87 ... //reuse x and y 88 } //implict calls: ^?{}(y), ^?{}(x) 96 89 \end{cfacode} 97 The language guarantees that every object and all their fields are constructed. Like \CC construction is automatically done on declaration and destruction done when the declared variables reach the end of its scope. 90 The language guarantees that every object and all their fields are constructed. Like \CC, construction of an object is automatically done on allocation and destruction of the object is done on deallocation. Allocation and deallocation can occur on the stack or on the heap. 91 \begin{cfacode} 92 { 93 struct S s = {10}; //allocation, call constructor 94 ... 95 } //deallocation, call destructor 96 struct S * s = new(); //allocation, call constructor 97 ... 98 delete(s); //deallocation, call destructor 99 \end{cfacode} 100 Note that like \CC, \CFA introduces \code{new} and \code{delete}, which behave like \code{malloc} and \code{free} in addition to constructing and destructing objects, after calling \code{malloc} and before calling \code{free} respectively. 98 101 99 For more information see \cite{cforall-ug,rob-thesis,www-cfa}.102 For more information on \CFA see \cite{cforall-ug,rob-thesis,www-cfa}.
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