From 0b207132e1f195cc6d962e37392a8e2cb2b434d6 Mon Sep 17 00:00:00 2001
From: tomsmeding <tom.smeding@gmail.com>
Date: Fri, 10 Mar 2017 08:42:43 +0100
Subject: Make multithreading work

---
 .gitignore |  2 ++
 Makefile   |  3 ++-
 roots.cpp  | 25 ++++++++++++++++---------
 3 files changed, 20 insertions(+), 10 deletions(-)

diff --git a/.gitignore b/.gitignore
index 04ab9e4..f470cfc 100644
--- a/.gitignore
+++ b/.gitignore
@@ -1,3 +1,5 @@
 roots
 *.o
 *.swp
+out.txt
+out.png
diff --git a/Makefile b/Makefile
index ccea193..69b46fb 100644
--- a/Makefile
+++ b/Makefile
@@ -1,5 +1,6 @@
 CXX = g++
 CXXFLAGS = -Wall -Wextra -std=c++11 -O2 -fwrapv
+LDFLAGS = -pthread
 
 .PHONY: all clean remake
 
@@ -13,7 +14,7 @@ remake: clean
 
 
 roots: $(patsubst %.cpp,%.o,$(wildcard *.cpp))
-	$(CXX) -o $@ $^
+	$(CXX) -o $@ $^ $(LDFLAGS)
 
 %.o: %.cpp $(wildcard *.h)
 	$(CXX) $(CXXFLAGS) -c -o $@ $<
diff --git a/roots.cpp b/roots.cpp
index d0cffe7..25102ba 100644
--- a/roots.cpp
+++ b/roots.cpp
@@ -235,14 +235,14 @@ void check(const vector<Com> &v){
 namespace Gens {
 	class Generator{
 	public:
-		virtual Polynomial get(i64 n);
-		virtual i64 total();
+		virtual Polynomial get(i64 n) const = 0;
+		virtual i64 total() const = 0;
 	};
 
 	template <int N,int D>
 	class Christensen : public Generator{
 	public:
-		Polynomial get(i64 n){
+		Polynomial get(i64 n) const {
 			int d=1;
 			while(d<=D){
 				i64 p=ipow(2*N+1,d);
@@ -260,7 +260,7 @@ namespace Gens {
 			return poly;
 		}
 
-		i64 total(){
+		i64 total() const {
 			i64 n=0;
 			for(int d=1;d<=D;d++){
 				n+=ipow(2*N+1,d);
@@ -272,7 +272,7 @@ namespace Gens {
 	template <int D>
 	class Derbyshire : public Generator{
 	public:
-		Polynomial get(i64 n){
+		Polynomial get(i64 n) const {
 			n+=2;
 			const int d=ilog(n);
 			if(d>D)return {};
@@ -284,7 +284,7 @@ namespace Gens {
 			return poly;
 		}
 
-		i64 total(){
+		i64 total() const {
 			return (1<<(D+1))-2;
 		}
 	};
@@ -358,7 +358,7 @@ struct Settings{
 };
 
 
-void tallyThreadFunc(Gens::Generator &gen,i64 start,i64 end,int *tally,const Settings &S){
+void tallyThreadFunc(const Gens::Generator &gen,i64 start,i64 end,int *tally,const Settings &S){
 	for(i64 index=start;index<end;index++){
 		const Polynomial &poly=gen.get(index);
 		vector<Com> r=FR::allroots(poly);
@@ -385,25 +385,32 @@ int main(int argc,char **argv){
 
 	if(argc==1){
 		// Gens::Christensen<4,5> gen;
-		Gens::Derbyshire<15> gen;
+		Gens::Derbyshire<20> gen;
 		i64 ntotal=gen.total();
 		int ncores=thread::hardware_concurrency();
 		cerr<<"Factoring "<<ntotal<<" polynomials..."<<endl;
-		cerr<<"Using "<<ncores<<" threads"<<endl;
+		cerr<<"Using "<<ncores<<" thread"<<(ncores==1?"":"s")<<endl;
 		thread ths[ncores];
 		int **tallies=new int*[ncores];
+		cerr<<"Spawning threads: ";
 		for(int i=0;i<ncores;i++){
 			tallies[i]=new int[S.width*S.height]();
 			ths[i]=thread(tallyThreadFunc,gen,ntotal*i/ncores,ntotal*(i+1)/ncores,tallies[i],S);
+			if(i!=0)cerr<<", ";
+			cerr<<i;
 		}
+		cerr<<endl<<"Joining threads: ";
 		tally=new int[S.width*S.height];
 		for(int i=0;i<ncores;i++){
 			ths[i].join();
+			if(i!=0)cerr<<", ";
+			cerr<<i;
 			for(int j=0;j<S.width*S.height;j++){
 				tally[j]+=tallies[i][j];
 			}
 			delete[] tallies[i];
 		}
+		cerr<<endl;
 
 		cerr<<"Writing data..."<<endl;
 		writeData("out.txt",tally,S.width,S.height);
-- 
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