runtime: add parallel for algorithm
This is factored out part of:
https://golang.org/cl/5279048/
(parallel GC)
R=bsiegert, mpimenov, rsc, minux.ma, r
CC=golang-dev
https://golang.org/cl/5986054
diff --git a/src/pkg/runtime/runtime.h b/src/pkg/runtime/runtime.h
index 672e05b..15f5fa3 100644
--- a/src/pkg/runtime/runtime.h
+++ b/src/pkg/runtime/runtime.h
@@ -73,6 +73,8 @@
typedef struct Timer Timer;
typedef struct GCStats GCStats;
typedef struct LFNode LFNode;
+typedef struct ParFor ParFor;
+typedef struct ParForThread ParForThread;
/*
* per-cpu declaration.
@@ -359,6 +361,27 @@
uintptr pushcnt;
};
+// Parallel for descriptor.
+struct ParFor
+{
+ void (*body)(ParFor*, uint32); // executed for each element
+ uint32 done; // number of idle threads
+ uint32 nthr; // total number of threads
+ uint32 nthrmax; // maximum number of threads
+ uint32 thrseq; // thread id sequencer
+ uint32 cnt; // iteration space [0, cnt)
+ void *ctx; // arbitrary user context
+ bool wait; // if true, wait while all threads finish processing,
+ // otherwise parfor may return while other threads are still working
+ ParForThread *thr; // array of thread descriptors
+ // stats
+ uint64 nsteal;
+ uint64 nstealcnt;
+ uint64 nprocyield;
+ uint64 nosyield;
+ uint64 nsleep;
+};
+
/*
* defined macros
* you need super-gopher-guru privilege
@@ -669,6 +692,18 @@
LFNode* runtime·lfstackpop(uint64 *head);
/*
+ * Parallel for over [0, n).
+ * body() is executed for each iteration.
+ * nthr - total number of worker threads.
+ * ctx - arbitrary user context.
+ * if wait=true, threads return from parfor() when all work is done;
+ * otherwise, threads can return while other threads are still finishing processing.
+ */
+ParFor* runtime·parforalloc(uint32 nthrmax);
+void runtime·parforsetup(ParFor *desc, uint32 nthr, uint32 n, void *ctx, bool wait, void (*body)(ParFor*, uint32));
+void runtime·parfordo(ParFor *desc);
+
+/*
* This is consistent across Linux and BSD.
* If a new OS is added that is different, move this to
* $GOOS/$GOARCH/defs.h.
