add one-threaded C example

C-optimized/makefile

@@ -12,6 +12,9 @@ CC=gcc
 SRC=samples.c
 OUTPUT=out/samples
 
+SRC_ONE_THREAD=./samples-one-thread.c
+OUTPUT_ONE_THREAD=out/samples-one-thread
+
 ## Dependencies
 #  Has no dependencies
 MATH=-lm
@@ -30,24 +33,20 @@ FORMATTER=clang-format -i -style=$(STYLE_BLUEPRINT)
 ## make build
 build: $(SRC)
 	$(CC) $(OPTIMIZED) $(DEBUG) $(SRC) $(OPENMP) $(MATH) -o $(OUTPUT)
-	
-#fast: Has been removed, compilation of "build" is very fast and it outputs optimized code by default
+	$(CC) $(OPTIMIZED) $(DEBUG) $(SRC_ONE_THREAD) $(OPENMP) $(MATH) -o $(OUTPUT_ONE_THREAD)
 
 format: $(SRC)
 	$(FORMATTER) $(SRC)
 
 run: $(SRC) $(OUTPUT)
 	OMP_NUM_THREADS=1 ./$(OUTPUT)
-
-multi: $(SRC) $(OUTPUT)
-	OMP_NUM_THREADS=1 ./$(OUTPUT) && echo
-	OMP_NUM_THREADS=2 ./$(OUTPUT) && echo
-	OMP_NUM_THREADS=4 ./$(OUTPUT)
+	./$(OUTPUT_ONE_THREAD)
 
 time:
 	OMP_NUM_THREADS=1 /bin/time -f "Time: %es" ./$(OUTPUT) && echo
 	OMP_NUM_THREADS=2 /bin/time -f "Time: %es" ./$(OUTPUT) && echo
 	OMP_NUM_THREADS=4 /bin/time -f "Time: %es" ./$(OUTPUT) && echo
+	/bin/time -f "Time: %es" ./$(OUTPUT_ONE_THREAD) && echo
 
 linux-install:
 	sudo apt-get install libomp-dev

C-optimized/samples-one-thread.c

@@ -0,0 +1,183 @@
+#include <math.h>
+#include <stdio.h>
+#include <stdlib.h>
+#include <time.h>
+
+const float PI = 3.14159265358979323846;
+
+#define N 1000000
+
+//Array helpers
+
+void array_print(float* array, int length)
+{
+    for (int i = 0; i < length; i++) {
+        printf("item[%d] = %f\n", i, array[i]);
+    }
+    printf("\n");
+}
+
+void array_fill(float* array, int length, float item)
+{
+    int i;
+    {
+        for (i = 0; i < length; i++) {
+            array[i] = item;
+        }
+    }
+}
+
+float array_sum(float* array, int length)
+{
+    float output = 0.0;
+    for (int i = 0; i < length; i++) {
+        output += array[i];
+    }
+    return output;
+}
+
+void array_cumsum(float* array_to_sum, float* array_cumsummed, int length)
+{
+    array_cumsummed[0] = array_to_sum[0];
+    for (int i = 1; i < length; i++) {
+        array_cumsummed[i] = array_cumsummed[i - 1] + array_to_sum[i];
+    }
+}
+
+float rand_float(float to)
+{
+    return ((float)rand() / (float)RAND_MAX) * to;
+}
+
+float ur_normal()
+{
+    float u1 = rand_float(1.0);
+    float u2 = rand_float(1.0);
+    float z = sqrtf(-2.0 * log(u1)) * sin(2 * PI * u2);
+    return z;
+}
+
+inline float random_uniform(float from, float to)
+{
+    return ((float)rand() / (float)RAND_MAX) * (to - from) + from;
+}
+
+inline float random_normal(float mean, float sigma)
+{
+    return (mean + sigma * ur_normal());
+}
+
+inline float random_lognormal(float logmean, float logsigma)
+{
+    return expf(random_normal(logmean, logsigma));
+}
+
+inline float random_to(float low, float high)
+{
+    const float NORMAL95CONFIDENCE = 1.6448536269514722;
+    float loglow = logf(low);
+    float loghigh = logf(high);
+    float logmean = (loglow + loghigh) / 2;
+    float logsigma = (loghigh - loglow) / (2.0 * NORMAL95CONFIDENCE);
+    return random_lognormal(logmean, logsigma);
+}
+
+void array_random_to(float* array, int length, float low, float high)
+{
+    int i;
+    #pragma omp private(i)
+    {
+        #pragma omp for
+        for (i = 0; i < length; i++) {
+            array[i] = random_to(low, high);
+        }
+    }
+}
+
+void mixture(float (*samplers[])(void), float* weights, int n_dists, float* results, int results_length)
+{
+    float sum_weights = array_sum(weights, n_dists);
+    float* normalized_weights = malloc(n_dists * sizeof(float));
+    for (int i = 0; i < n_dists; i++) {
+        normalized_weights[i] = weights[i] / sum_weights;
+    }
+
+    float* cummulative_weights = malloc(n_dists * sizeof(float));
+    array_cumsum(normalized_weights, cummulative_weights, n_dists);
+
+    //create var holders
+    float p1;
+    int sample_index, i, own_length;
+
+    {
+			for (int i = 0; i < results_length; i++) {
+					p1 = random_uniform(0, 1);
+					for (int j = 0; j < n_dists; j++) {
+							if (p1 < cummulative_weights[j]) {
+									results[i] = samplers[j]();
+									break;
+							}
+					}
+			}
+    }
+    free(normalized_weights);
+    free(cummulative_weights);
+}
+
+float sample_0()
+{
+    return 0;
+}
+
+float sample_1()
+{
+    return 1;
+}
+
+float sample_few()
+{
+    return random_to(1, 3);
+}
+
+float sample_many()
+{
+    return random_to(2, 10);
+}
+
+int main()
+{
+    //initialize randomness
+    srand(1);
+    
+		// clock_t start, end;
+		// start = clock();
+
+		// Toy example
+		// Declare variables in play
+		float p_a, p_b, p_c;
+		// printf("Max threads: %d\n", n_threads);
+		// omp_set_num_threads(n_threads);
+
+		// Initialize variables
+		p_a = 0.8;
+		p_b = 0.5;
+		p_c = p_a * p_b;
+
+		// Generate mixture
+		int n_dists = 4;
+		float weights[] = { 1 - p_c, p_c / 2, p_c / 4, p_c / 4 };
+		float (*samplers[])(void) = { sample_0, sample_1, sample_few, sample_many };
+
+		float* results = malloc(N * sizeof(float));
+		mixture(samplers, weights, n_dists, results, N);
+		printf("Sum(dist_mixture, N)/N = %f\n", array_sum(results, N) / N);
+		// array_print(dist_mixture[0], N);
+		
+		// end = clock();
+		// printf("Time (ms): %f\n", ((double)(end - start)) / (CLOCKS_PER_SEC * 10) * 1000);
+		// ^ Will only measure how long it takes the inner main to run, not the whole program, 
+		// including e.g., loading the program into memory or smth.
+		// Also CLOCKS_PER_SEC in POSIX is a constant equal to 1000000.
+		// See: https://stackoverflow.com/questions/10455905/why-is-clocks-per-sec-not-the-actual-number-of-clocks-per-second
+    return 0;
+}