From f3129294bf92daae6ca72e2f8c456bdff97b8b3e Mon Sep 17 00:00:00 2001
From: Julian Weigt <juw@posteo.de>
Date: Tue, 23 Dec 2025 19:27:46 +0000
Subject: Enable multithreading.

---
 charf.c | 62 +++++++++++++++++++++++++++++++++++++++++++++++++++++---------
 1 file changed, 53 insertions(+), 9 deletions(-)

diff --git a/charf.c b/charf.c
index a2d1ad8..f52d41e 100644
--- a/charf.c
+++ b/charf.c
@@ -2,11 +2,14 @@
 #include <stdlib.h>
 #include <math.h>
 #include <pthread.h>
+#include <assert.h>
 
 #ifndef EXACT
 #define EXACT false
 #endif
 
+#define NUM_THREADS 4
+
 #if EXACT
 #include "ratio.h"
 #define VALUETYPE rational
@@ -106,8 +109,8 @@ void compute(int N, int K, int D, EXPTYPE p, int t){
 	//for(int i=0;i<N;i++) f[N+i] = rand() %2;
 	/*In the middle of the domain set f to the values encoded in bit string t*/
 	for(int i=0;i<N;i++){
-		/*Since we care about the Kth derivative, which in i depends on f on [i,i+K], shift f to the right by K/2 so that the most interesting part of f^{(K)} and Mf^{(K)} will be around the center of the domain*/
-		f[(D-N)/2+i+K/2] = convert_int((t >> i) & 1);
+		/*Since we care about the Kth derivative, which in i depends on f on [i,i+K], shift f to the right by K so that the support of f^{(K)} stays within the domain.*/
+		f[(D-(N+K))/2+K+i] = convert_int((t >> i) & 1);
 		//if(i%3==0) f[2*N+i+K/2] = 1;
 	}
 
@@ -147,8 +150,9 @@ void compute(int N, int K, int D, EXPTYPE p, int t){
 
 	//printf("%.3d: %.3f  \n",t,r);
 	/*Print f and ||Mf^{(k)}||_p/||f^{(k)}||_p if the latter is close to 1/2.*/
-	if(to_double(r)>.4997){
-	//if(to_double(r)>.7)
+	//if(to_double(r)>.4997)
+	if(to_double(r)>.6)
+	{
 		printf("f: ");
 		for(int i=0;i<D;i++) printf("%1.0f ",to_double(f[i]));
 		printf("\n");
@@ -158,21 +162,61 @@ void compute(int N, int K, int D, EXPTYPE p, int t){
 	free(Mf);
 }
 
+struct Args {int* N; int* K; int* D; EXPTYPE* p; int* t; };
+
+void* perform_work(void* arguments){
+	struct Args *args = arguments;
+	int N = *(args->N);
+	int K = *(args->K);
+	int D = *(args->D);
+	EXPTYPE p = *(args->p);
+	int* s = args->t;
+
+	while(*s <= (1 << N)-1){
+		int t = *s;
+		*s = t+1;
+		compute(N,K,D,p,t);
+	}
+	return NULL;
+}
+
 int main() {
 	/*length of the support of f*/
-	int N=12;
+	int N=16;
 
 	/*order of the derivative to consider. Should not be larger than (D-N)/2 because then the support of f^{(K)} reaches outside of our domain.*/
-	int K=3;
+	int K=10;
 
-	/*length of the domain*/
-	int D=N+K+1;
+	/*length of the domain, minimum N+K to make sure the support of f^{(k)} belongs to the domain*/
+	int D=N+K+N/2;
 
 	/*exponent p of the L^p norm to consider*/
 	EXPTYPE p = 1;
 
+	int t = 1;
 	/*Iterate over all strings of 0s and 1s with length N. Those will represent f.*/
-	for(int t=1; t<=(1 << N)-1; t++) compute(N,K,D,p,t);
+
+	//for(int t=1; t<=(1 << N)-1; t++){
+		//compute(N,K,D,p,t);
+	//}
+
+	struct Args args = {&N, &K, &D, &p, &t};
+
+	pthread_t threads[NUM_THREADS];
+	int result_code;
+
+	for (int i = 0; i < NUM_THREADS; i++) {
+		printf("In main: Creating thread %d.\n", i);
+		result_code = pthread_create(&threads[i], NULL, perform_work, &args);
+		assert(!result_code);
+	}
+
+	// wait for each thread to complete
+	for (int i = 0; i < NUM_THREADS; i++) {
+		result_code = pthread_join(threads[i], NULL);
+		assert(!result_code);
+		printf("In main: Thread %d has ended.\n", i);
+	}
 
 	return 0;
 }
-- 
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