source: CIVL/notes/notes.txt@ dfb0fef

TASS incorporation:

Model:

  Types:
    MPIComm
    MPIStatus
    MPIRequest
    
  Constants:
    MPI_INT, MPI_DOUBLE, MPI_FLOAT, MPI_CHAR, ...
    MPI_
  
  Statements:
  MPISendStatement
  MPIRecvStatement
  MPIBarrierStatement
  MPIIsendStatement
  MPIIrecvStatement
  MPIWaitStatement
  
  Expressions:
  NemptyExpression
  NfullExpression

State: communicator? good enough for blocking communication.
nonblocking requires more stateful message (see MPI Spin)

ModelBuilder:
needs to work from AST which is C+MPI code.

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Fundamentals:

expression: $length(array)
expression: $append(array, element)
$concatenate, $remove, 

/* A system type for any segment of memory used as a buffer,
 * formed using union types */
typedef struct __bundle__ $bundle;

/* Creates a buffer from the memory region specified by
 * ptr and size, copying the data into the new buffer */
$bundle $bundle_pack(void *ptr, int size);

/* Copies the data out of the buffer into the region
 * specified */
void $bundle_unpack($bundle bundle, void *ptr, int size);

/* creates a new comm from the given sequence of processes,
 * by allocating memory and copying the process sequence;
 * the new comm has no messages */
$comm $comm_create(int nprocs, $proc * procs);

/* adds the message to the comm */
void $comm_enqueue($comm * comm, $message * message);

/* finds the first matching message, removes it from
 * comm, and returns pointer to message */ 
$message * $comm_dequeue($comm * comm, int source, int dest, int tag);


Action Plan:
  - add a CIVLBundleType, similar to CIVLHeapType
  - collect all types during model building
  - complete the CIVLBundleType by giving it the list of all types,
    and the symbolic type which is the union of array of t_i
  - defined $bundle_pack in executor by:
    1. let v = dereference ptr* (just first element)
    2. let t = v.type();
    3. array-of-t is the type of the bundle you will make by cases:
a. is ptr to a variable, or an array element pointer, etc.
create the new value of type array-of-t.
    4. cast that to type bundleSymbolicType.
    5. assign it to lhs.




Consider CIVL-C dropping C's awful pointer-array pun.
No automatic conversions. (Just drop them if language is CIVL-C).

f(double[] a) : really takes an array of double, not pointer.
double[] f(...) : returns an array of double

To get the C behavior:

f(double *p) {...}

to call f: f(&a[0]);






How hard would it be to add a new type: $sequence<T>
to the language?  Like vector or variable length array.
Then define functions like $append, $add, $remove,
$subseq, blah blah: but these are all generic.
Need concept of generic functions.  Could make them
operations.

$buffer $buffer_create(void *ptr, $type element_type, int count);

$buffer $buffer_pack(void *ptr, int size);

Problem: what if type of ptr is just void*.  Won't know statically
all the types to form the union type.  Without some sort of flow
analysis, will have to assume every type is possible.

flow analysis: look at occurrences of $buffer_pack
if type of expression ptr is void*, look at what goes into that
expression.  pointer arithmetic: ptr argument, trace back
through assignments, function calls. forget it.

need union of all types.

**** collect all types used in model ****  easy



do essentially the same thing, but take different args.
If the element type is complete (and hence can use sizeof)
the first can be defined as
    $buffer_pack(ptr, count*sizeof(t))



Messages:

$message_pack has to produce a message, but how?
Use union type.
Union over all types which can occur in message_pack.
Inject.
Need to extract value from slice of array.
Wish I had symbolic operators for that.
Could be single variable, entire array, slice of array
slice of array: copy elements if concrete bounds, else
need array - lambda (not yet implemented)

stick in union type.

tyedef struct __buffer__ __buffer__;
typedef struct __message__ {
  int source;
  int dest;
  int tag;
  __buffer__ data;
  int size;
}

Translate __buffer__ to CIVLBufferType.
Symbolic type: symbolicBufferType:
Union-of-array-of-t_i, where t_i ranges over all types
occuring in message pack calls.   

Implement $message_pack : just to create buffer


How about relaxing restriction from C that element types of
arrays must be complete?  Instead just generate error
if you try to take sizeof such a thing. 
Instead of 
(double*)$malloc(&h, size)
  how about
$alloc(&h, typeof(double), count);

void* $alloc($heap *h, $type type, int count);

Add to grammar: "$typeof(sizeable)" just like sizeof, but
don't care about completeness.
no sizeof required.  Type of typeof is $dynamic.  Why not "type".
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