• Charles Hixson (59/59) Nov 22 2013 Is this a plausible approach?

Charles Hixson <charleshixsn earthlink.net> writes:

Is this a plausible approach?
What I've sketched out so far is:
/**    cells2.d    */

import    std.concurrency;
import    std.stdio;

import    cellsdb;

Tid    tids[8];

void    cellLoop (int i)
{    Cells[ulong]    cells;
     bool    rcv    =    true;
     int    thisTin    =    i;
     for(;;)
     {    foreach    (k, v; cells)
         {
             while    (rcv)
             {    rcv    =    receiveTimeout (0,
                     //TODO  Write the messages that actually do the work.
                     (Variant    any)
                         {    writefln ("cellLoop couldn't handle 
receiving {0}".
                                     format(any.type);
                         }
             }
             //TODO    housekeeping on cells.
         }    //    foreach    (k, v; cells)
         //TODO    handle any deletions from cells
     }    //    for(;;)
}  // cellLoop


should be found.     */
Tin    idToTin (ulong    id)
{    return    (id / 2^13) % tids.length;    }

void    main()
{
     for    (int i = 0;    i < tids.length;    i++)    tids[i] =    
spawn (&cellLoop, i);
    //TODO  start the threads working
}


There's a bunch of other code, but it's off the point.  Part of the 
reason for the idToTin method is that cells close together are expected 
to make mutual calls more often.  My expectation is that message passing 
is more expensive than subroutine calls, so if calls are within the same 
thread, they can be called directly rather than making message passing 
invocations.  I'm sharing the array of Tids, but it's only written 
once.  I'd make it immutable if I could figure out how...short of 
wrapping everything in a class with an init method.

The basic (questionable) idea here is that the best way to step through 
an AA is to use foreach, so the if I want to do the housekeeping in 
short runs (so the threads don't slow interaction) I need to have the 
receive within the foreach.  The alternative approach I came up with is 
to store the data in a RedBlack tree, which would make it easy to 
interrupt and resume whenever I needed, but which is less efficient for 
access than a hash table.  The penalty is that I ALWAY do at least one 
housekeeping task between each receive.  Also, when I need to break out 
of the inner loop to allow for cell deletion, I start over from the 
beginning, without ever having processed the end.  Not good, as cell 
deletions aren't expected to be all that rare.

-- 
Charles Hixson