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rayfifo.c
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Mon, Jul 8, 21:40

rayfifo.c
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#ifndef lint
static const char RCSid[] = "$Id: rayfifo.c,v 2.6 2018/05/02 20:42:21 greg Exp $";
#endif
/*
* rayfifo.c - parallelize ray queue that respects order
*
* External symbols declared in ray.h
*/
#include "copyright.h"
/*
* These routines are essentially an adjunct to raypcalls.c, providing
* a convenient means to get first-in/first-out behavior from multiple
* processor cores. The interface is quite simple, with two functions
* and a callback, which must be defined by the calling program. The
* hand-off for finished rays is assigned to ray_fifo_out, which takes
* a single pointer to the finished ray and returns a non-negative
* integer. If there is an exceptional condition where termination
* is desired, a negative value may be returned.
*
* The ray_fifo_in() call takes a ray that has been initialized in
* the same manner as for the ray_pqueue() call, i.e., rayorigin()
* has been called and the origin, direction and maximum distance
* have all been assigned. However, the ray number will be reset
* by ray_fifo_in() according to the number of rays traced since the
* last call to ray_fifo_flush(). This final call completes all
* pending ray calculations and frees the FIFO buffer. If any of
* the automatic calls to the ray_fifo_out callback return a
* negative value, processing stops and -1 is returned.
*
* Note: The ray passed to ray_fifo_in() may be overwritten
* arbitrarily, since it is passed to ray_pqueue().
*/
#include "ray.h"
#include <string.h>
#ifndef MAXFIFO
#define MAXFIFO 4096 /* clear FIFO past this */
#endif
int (*ray_fifo_out)(RAY *r) = NULL; /* ray output callback */
static RAY *r_fifo_buf = NULL; /* circular FIFO out buffer */
static int r_fifo_len = 0; /* allocated FIFO length */
static RNUMBER r_fifo_start = 1; /* first awaited ray */
static RNUMBER r_fifo_end = 1; /* one past FIFO last */
static RNUMBER r_fifo_next = 1; /* next ray assignment */
#define r_fifo(rn) (&r_fifo_buf[(rn)&(r_fifo_len-1)])
static void
ray_fifo_growbuf(void) /* double buffer size (or set to minimum if NULL) */
{
RAY *old_buf = r_fifo_buf;
int old_len = r_fifo_len;
int i;
if (r_fifo_buf == NULL)
r_fifo_len = 1<<5; /* must be power of two */
else
r_fifo_len <<= 1;
/* allocate new */
r_fifo_buf = (RAY *)calloc(r_fifo_len, sizeof(RAY));
if (r_fifo_buf == NULL)
error(SYSTEM, "out of memory in ray_fifo_growbuf");
if (old_buf == NULL)
return;
/* copy old & free */
for (i = r_fifo_start; i < r_fifo_end; i++)
*r_fifo(i) = old_buf[i&(old_len-1)];
free(old_buf);
}
static int
ray_fifo_push( /* send finished ray to output (or queue it) */
RAY *r
)
{
int rv, nsent = 0;
if (ray_fifo_out == NULL)
error(INTERNAL, "ray_fifo_out is NULL");
if ((r->rno < r_fifo_start) | (r->rno >= r_fifo_next))
error(INTERNAL, "unexpected ray number in ray_fifo_push()");
if (r->rno > r_fifo_start) { /* insert into output queue */
while (r->rno - r_fifo_start >= r_fifo_len)
ray_fifo_growbuf(); /* need more space */
*r_fifo(r->rno) = *r;
if (r->rno >= r_fifo_end)
r_fifo_end = r->rno + 1;
return(0);
}
/* r->rno == r_fifo_start, so transfer ray(s) */
do {
rv = (*ray_fifo_out)(r);
r->rno = 0; /* flag this entry complete */
if (rv < 0)
return(-1);
nsent += rv;
if (++r_fifo_start < r_fifo_end)
r = r_fifo(r_fifo_start);
else if (r_fifo_start > r_fifo_end)
r_fifo_end = r_fifo_start;
} while (r->rno == r_fifo_start);
return(nsent);
}
int
ray_fifo_in( /* add ray to FIFO */
RAY *r
)
{
static int incall = 0; /* prevent recursion */
int rv, rval = 0;
if (incall++)
error(INTERNAL, "recursive call to ray_fifo_in()");
/* need to reset our FIFO? */
if ((r_fifo_start >= 1L<<30) | (r_fifo_len > MAXFIFO)) {
if ((rv = ray_fifo_flush()) < 0)
{--incall; return(-1);}
rval += rv;
}
/* queue ray */
r->rno = r_fifo_next++;
if ((rv = ray_pqueue(r)) < 0)
{--incall; return(-1);}
if (!rv) /* no result this time? */
{--incall; return(rval);}
do { /* else send/queue result */
if ((rv = ray_fifo_push(r)) < 0)
{--incall; return(-1);}
rval += rv;
} while (ray_presult(r, -1) > 0); /* empty in-core queue */
--incall; return(rval);
}
int
ray_fifo_flush(void) /* flush everything and release buffer */
{
RAY myRay;
int rv, rval = 0;
/* clear parallel queue */
while ((rv = ray_presult(&myRay, 0)) > 0 &&
(rv = ray_fifo_push(&myRay)) >= 0)
rval += rv;
if (rv < 0) /* check for exception */
return(-1);
if (r_fifo_start != r_fifo_end)
error(INTERNAL, "could not empty queue in ray_fifo_flush()");
if (r_fifo_buf != NULL) {
free(r_fifo_buf);
r_fifo_buf = NULL; r_fifo_len = 0;
}
r_fifo_next = r_fifo_end = r_fifo_start = 1;
return(rval);
}

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