From 69d08caec1934656ce884ae61cb182456244d702 Mon Sep 17 00:00:00 2001
From: Oliver Tonnhofer <olt@bogosoft.com>
Date: Wed, 18 Sep 2013 11:25:49 +0200
Subject: [PATCH] optimize number of goroutines during reading

---
 reader/reader.go      | 12 +++++++-----
 reader/reader_test.go | 32 ++++++++++++++++++++++++++++++++
 2 files changed, 39 insertions(+), 5 deletions(-)
 create mode 100644 reader/reader_test.go

diff --git a/reader/reader.go b/reader/reader.go
index f511271..4a37249 100644
--- a/reader/reader.go
+++ b/reader/reader.go
@@ -1,6 +1,7 @@
 package reader
 
 import (
+	"math"
 	"os"
 	"runtime"
 	"strconv"
@@ -34,11 +35,6 @@ func init() {
 	if os.Getenv("IMPOSM_SKIP_WAYS") != "" {
 		skipWays = true
 	}
-	nParser = int64(runtime.NumCPU())
-	nWays = int64(runtime.NumCPU())
-	nRels = int64(runtime.NumCPU())
-	nNodes = int64(runtime.NumCPU())
-	nCoords = int64(runtime.NumCPU())
 	if procConf := os.Getenv("IMPOSM_READ_PROCS"); procConf != "" {
 		parts := strings.Split(procConf, ":")
 		nParser, _ = strconv.ParseInt(parts[0], 10, 32)
@@ -46,8 +42,14 @@ func init() {
 		nWays, _ = strconv.ParseInt(parts[2], 10, 32)
 		nNodes, _ = strconv.ParseInt(parts[3], 10, 32)
 		nCoords, _ = strconv.ParseInt(parts[3], 10, 32)
+	} else {
+		nParser, nRels, nWays, nNodes, nCoords = readersForCpus(runtime.NumCPU())
 	}
+}
 
+func readersForCpus(cpus int) (int64, int64, int64, int64, int64) {
+	cpuf := float64(cpus)
+	return int64(math.Ceil(cpuf * 0.75)), int64(math.Ceil(cpuf * 0.25)), int64(math.Ceil(cpuf * 0.25)), int64(math.Ceil(cpuf * 0.25)), int64(math.Ceil(cpuf * 0.25))
 }
 
 func ReadPbf(cache *osmcache.OSMCache, progress *stats.Statistics,
diff --git a/reader/reader_test.go b/reader/reader_test.go
new file mode 100644
index 0000000..7ee9d4e
--- /dev/null
+++ b/reader/reader_test.go
@@ -0,0 +1,32 @@
+package reader
+
+import (
+	"testing"
+)
+
+func TestReaderCpus(t *testing.T) {
+	p, r, w, n, c := readersForCpus(1)
+	if p != 1 && r != 1 && w != 1 && n != 1 && c != 1 {
+		t.Fatal(p, r, w, n, c)
+	}
+
+	p, r, w, n, c = readersForCpus(2)
+	if p != 2 && r != 1 && w != 1 && n != 1 && c != 1 {
+		t.Fatal(p, r, w, n, c)
+	}
+
+	p, r, w, n, c = readersForCpus(4)
+	if p != 3 && r != 1 && w != 1 && n != 1 && c != 1 {
+		t.Fatal(p, r, w, n, c)
+	}
+
+	p, r, w, n, c = readersForCpus(8)
+	if p != 6 && r != 2 && w != 2 && n != 2 && c != 2 {
+		t.Fatal(p, r, w, n, c)
+	}
+
+	p, r, w, n, c = readersForCpus(12)
+	if p != 8 && r != 3 && w != 3 && n != 3 && c != 3 {
+		t.Fatal(p, r, w, n, c)
+	}
+}