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#ifndef lint
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static const char RCSid[] = "$Id: rayfifo.c,v 2.5 2018/04/26 18:09:55 greg Exp $";
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#endif
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/*
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* rayfifo.c - parallelize ray queue that respects order
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*
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* External symbols declared in ray.h
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*/
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#include "copyright.h"
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/*
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* These routines are essentially an adjunct to raypcalls.c, providing
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* a convenient means to get first-in/first-out behavior from multiple
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* processor cores. The interface is quite simple, with two functions
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* and a callback, which must be defined by the calling program. The
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* hand-off for finished rays is assigned to ray_fifo_out, which takes
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* a single pointer to the finished ray and returns a non-negative
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* integer. If there is an exceptional condition where termination
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* is desired, a negative value may be returned.
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*
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* The ray_fifo_in() call takes a ray that has been initialized in
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* the same manner as for the ray_pqueue() call, i.e., rayorigin()
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* has been called and the origin, direction and maximum distance
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* have all been assigned. However, the ray number will be reset
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* by ray_fifo_in() according to the number of rays traced since the
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* last call to ray_fifo_flush(). This final call completes all
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* pending ray calculations and frees the FIFO buffer. If any of
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* the automatic calls to the ray_fifo_out callback return a
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* negative value, processing stops and -1 is returned.
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*
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* Note: The ray passed to ray_fifo_in() may be overwritten
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* arbitrarily, since it is passed to ray_pqueue().
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*/
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#include "ray.h"
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#include <string.h>
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#ifndef MAXFIFO
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#define MAXFIFO 4096 /* clear FIFO past this */
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#endif
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int (*ray_fifo_out)(RAY *r) = NULL; /* ray output callback */
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static RAY *r_fifo_buf = NULL; /* circular FIFO out buffer */
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static int r_fifo_len = 0; /* allocated FIFO length */
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static RNUMBER r_fifo_start = 1; /* first awaited ray */
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static RNUMBER r_fifo_end = 1; /* one past FIFO last */
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static RNUMBER r_fifo_next = 1; /* next ray assignment */
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#define r_fifo(rn) (&r_fifo_buf[(rn)&(r_fifo_len-1)])
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static void
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ray_fifo_growbuf(void) /* double buffer size (or set to minimum if NULL) */
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{
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RAY *old_buf = r_fifo_buf;
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int old_len = r_fifo_len;
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int i;
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if (r_fifo_buf == NULL)
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r_fifo_len = 1<<5; /* must be power of two */
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else
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r_fifo_len <<= 1;
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/* allocate new */
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r_fifo_buf = (RAY *)calloc(r_fifo_len, sizeof(RAY));
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if (r_fifo_buf == NULL)
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error(SYSTEM, "out of memory in ray_fifo_growbuf");
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if (old_buf == NULL)
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return;
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/* copy old & free */
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for (i = r_fifo_start; i < r_fifo_end; i++)
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*r_fifo(i) = old_buf[i&(old_len-1)];
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free(old_buf);
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}
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static int
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ray_fifo_push( /* send finished ray to output (or queue it) */
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RAY *r
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)
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{
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int rv, nsent = 0;
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if (ray_fifo_out == NULL)
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error(INTERNAL, "ray_fifo_out is NULL");
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if ((r->rno < r_fifo_start) | (r->rno >= r_fifo_next))
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error(INTERNAL, "unexpected ray number in ray_fifo_push()");
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if (r->rno > r_fifo_start) { /* insert into output queue */
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while (r->rno - r_fifo_start >= r_fifo_len)
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ray_fifo_growbuf(); /* need more space */
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*r_fifo(r->rno) = *r;
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if (r->rno >= r_fifo_end)
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r_fifo_end = r->rno + 1;
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return(0);
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}
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/* r->rno == r_fifo_start, so transfer ray(s) */
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do {
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rv = (*ray_fifo_out)(r);
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r->rno = 0; /* flag this entry complete */
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if (rv < 0)
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return(-1);
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nsent += rv;
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if (++r_fifo_start < r_fifo_end)
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r = r_fifo(r_fifo_start);
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else if (r_fifo_start > r_fifo_end)
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r_fifo_end = r_fifo_start;
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} while (r->rno == r_fifo_start);
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return(nsent);
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}
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int
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ray_fifo_in( /* add ray to FIFO */
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RAY *r
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)
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{
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static int incall = 0; /* prevent recursion */
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int rv, rval = 0;
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if (incall++)
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error(INTERNAL, "recursive call to ray_fifo_in()");
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/* need to reset our FIFO? */
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if ((r_fifo_start >= 1L<<30) | (r_fifo_len > MAXFIFO)) {
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if ((rv = ray_fifo_flush()) < 0)
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{--incall; return(-1);}
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rval += rv;
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}
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/* queue ray */
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r->rno = r_fifo_next++;
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if ((rv = ray_pqueue(r)) < 0)
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{--incall; return(-1);}
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if (!rv) /* no result this time? */
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{--incall; return(rval);}
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do { /* else send/queue result */
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if ((rv = ray_fifo_push(r)) < 0)
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{--incall; return(-1);}
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rval += rv;
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} while (ray_presult(r, -1) > 0); /* empty in-core queue */
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--incall; return(rval);
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}
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int
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ray_fifo_flush(void) /* flush everything and release buffer */
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{
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RAY myRay;
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int rv, rval = 0;
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/* clear parallel queue */
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while ((rv = ray_presult(&myRay, 0)) > 0 &&
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(rv = ray_fifo_push(&myRay)) >= 0)
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rval += rv;
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if (rv < 0) /* check for exception */
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return(-1);
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if (r_fifo_start != r_fifo_end)
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error(INTERNAL, "could not empty queue in ray_fifo_flush()");
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if (r_fifo_buf != NULL) {
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free(r_fifo_buf);
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r_fifo_buf = NULL; r_fifo_len = 0;
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}
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r_fifo_next = r_fifo_end = r_fifo_start = 1;
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return(rval);
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}
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