C/alt/04-factor-out-paralellization/makefile

@@ -1,106 +0,0 @@
-# Interface: 
-#   make
-#   make build
-#   make format
-#   make run
-
-# Compiler
-CC=gcc
-# CC=tcc # <= faster compilation
-
-# Main file
-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
-
-## Flags
-DEBUG= #'-g'
-STANDARD=-std=c99
-WARNINGS=-Wall
-OPTIMIZED=-O3 #-O3 actually gives better performance than -Ofast, at least for this version
-OPENMP=-fopenmp
-
-## Formatter
-STYLE_BLUEPRINT=webkit
-FORMATTER=clang-format -i -style=$(STYLE_BLUEPRINT)
-
-## make build
-build: $(SRC)
-	$(CC) $(OPTIMIZED) $(DEBUG) $(SRC) $(OPENMP) $(MATH) -o $(OUTPUT)
-
-static:
-	$(CC) $(OPTIMIZED) $(DEBUG) $(SRC) $(OPENMP) $(MATH) -o $(OUTPUT)
-
-format: $(SRC)
-	$(FORMATTER) $(SRC)
-
-run: $(SRC) $(OUTPUT)
-	OMP_NUM_THREADS=1 ./$(OUTPUT) && echo
-
-multi:
-	OMP_NUM_THREADS=1 ./$(OUTPUT) && echo
-	OMP_NUM_THREADS=2 ./$(OUTPUT) && echo
-	OMP_NUM_THREADS=4 ./$(OUTPUT) && echo
-	OMP_NUM_THREADS=8 ./$(OUTPUT) && echo
-	OMP_NUM_THREADS=16 ./$(OUTPUT) && echo
-
-## Timing
-
-time-linux: 
-	@echo "Requires /bin/time, found on GNU/Linux systems" && echo
-	
-	@echo "Running 100x and taking avg time: OMP_NUM_THREADS=1 $(OUTPUT)"
-	@t=$$(/usr/bin/time -f "%e" -p bash -c 'for i in {1..100}; do OMP_NUM_THREADS=1 $(OUTPUT); done' 2>&1 >/dev/null | grep real | awk '{print $$2}' ); echo "scale=2; 1000 * $$t / 100" | bc | sed "s|^|Time using 1 thread: |" | sed 's|$$|ms|' && echo
-	
-	@echo "Running 100x and taking avg time: OMP_NUM_THREADS=2 $(OUTPUT)"
-	@t=$$(/usr/bin/time -f "%e" -p bash -c 'for i in {1..100}; do OMP_NUM_THREADS=2 $(OUTPUT); done' 2>&1 >/dev/null | grep real | awk '{print $$2}' ); echo "scale=2; 1000 * $$t / 100" | bc | sed "s|^|Time using 2 threads: |" | sed 's|$$|ms|' && echo
-	
-	@echo "Running 100x and taking avg time: OMP_NUM_THREADS=4 $(OUTPUT)"
-	@t=$$(/usr/bin/time -f "%e" -p bash -c 'for i in {1..100}; do OMP_NUM_THREADS=4 $(OUTPUT); done' 2>&1 >/dev/null | grep real | awk '{print $$2}' ); echo "scale=2; 1000 * $$t / 100" | bc | sed "s|^|Time for 4 threads: |" | sed 's|$$|ms|' && echo
-	
-	@echo "Running 100x and taking avg time: OMP_NUM_THREADS=8 $(OUTPUT)"
-	@t=$$(/usr/bin/time -f "%e" -p bash -c 'for i in {1..100}; do OMP_NUM_THREADS=8 $(OUTPUT); done' 2>&1 >/dev/null | grep real | awk '{print $$2}' ); echo "scale=2; 1000 * $$t / 100" | bc | sed "s|^|Time using 8 threads: |" | sed 's|$$|ms|' && echo
-	
-	@echo "Running 100x and taking avg time: OMP_NUM_THREADS=16 $(OUTPUT)"
-	@t=$$(/usr/bin/time -f "%e" -p bash -c 'for i in {1..100}; do OMP_NUM_THREADS=16 $(OUTPUT); done' 2>&1 >/dev/null | grep real | awk '{print $$2}' ); echo "scale=2; 1000 * $$t / 100" | bc | sed "s|^|Time using 16 threads: |" | sed 's|$$|ms|' && echo
-
-time-linux-fastest: 
-	@echo "Running 100x and taking avg time: OMP_NUM_THREADS=16 $(OUTPUT)"
-	@t=$$(/usr/bin/time -f "%e" -p bash -c 'for i in {1..100}; do OMP_NUM_THREADS=16 $(OUTPUT); done' 2>&1 >/dev/null | grep real | awk '{print $$2}' ); echo "scale=2; 1000 * $$t / 100" | bc | sed "s|^|Time using 16 threads: |" | sed 's|$$|ms|' && echo
-
-time-linux-simple:
-	@echo "Requires /bin/time, found on GNU/Linux systems" && echo
-	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" ./$(OUTPUT) && echo
-	OMP_NUM_THREADS=8 /bin/time -f "Time: %es" ./$(OUTPUT) && echo
-	OMP_NUM_THREADS=16 /bin/time -f "Time: %es" ./$(OUTPUT) && echo
-
-## Profiling
-
-profile-linux: 
-	echo "Requires perf, which depends on the kernel version, and might be in linux-tools package or similar"
-	echo "Must be run as sudo"
-	$(CC) $(SRC) $(OPENMP) $(MATH) -o $(OUTPUT)
-	# ./$(OUTPUT)
-	# gprof: 
-	# gprof $(OUTPUT) gmon.out > analysis.txt
-	# rm gmon.out
-	# vim analysis.txt
-	# rm analysis.txt
-	# perf: 
-	OMP_NUM_THREADS=16 sudo perf record $(OUTPUT)
-	sudo perf report
-	rm perf.data
-	
-
-## Install
-debian-install-dependencies:
-	sudo apt-get install libomp-dev
-

C/alt/04-factor-out-paralellization/samples.c

@@ -1,260 +0,0 @@
-#include <math.h>
-#include <omp.h>
-#include <stdint.h>
-#include <stdio.h>
-#include <stdlib.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");
-}
-
-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];
-    }
-}
-
-// Split array helpers
-int split_array_get_length(int index, int total_length, int n_threads)
-{
-    return (total_length % n_threads > index ? total_length / n_threads + 1 : total_length / n_threads);
-}
-
-void split_array_allocate(float** meta_array, int length, int divide_into)
-{
-    int split_array_length;
-
-    for (int i = 0; i < divide_into; i++) {
-        split_array_length = split_array_get_length(i, length, divide_into);
-        meta_array[i] = malloc(split_array_length * sizeof(float));
-    }
-}
-
-void split_array_free(float** meta_array, int divided_into)
-{
-    for (int i = 0; i < divided_into; i++) {
-        free(meta_array[i]);
-    }
-    free(meta_array);
-}
-
-float split_array_sum(float** meta_array, int length, int divided_into)
-{
-    int i;
-    float output = 0;
-
-#pragma omp parallel for reduction(+ \
-                                   : output)
-    for (int i = 0; i < divided_into; i++) {
-        float own_partial_sum = 0;
-        int split_array_length = split_array_get_length(i, length, divided_into);
-        for (int j = 0; j < split_array_length; j++) {
-            own_partial_sum += meta_array[i][j];
-        }
-        output += own_partial_sum;
-    }
-    return output;
-}
-
-// Pseudo Random number generator
-
-uint32_t xorshift32(uint32_t* seed)
-{
-    // Algorithm "xor" from p. 4 of Marsaglia, "Xorshift RNGs"
-    // See <https://stackoverflow.com/questions/53886131/how-does-xorshift32-works>
-    // https://en.wikipedia.org/wiki/Xorshift
-    // Also some drama: <https://www.pcg-random.org/posts/on-vignas-pcg-critique.html>, <https://prng.di.unimi.it/>
-
-    uint32_t x = *seed;
-    x ^= x << 13;
-    x ^= x >> 17;
-    x ^= x << 5;
-    return *seed = x;
-}
-
-// Distribution & sampling functions
-
-float rand_0_to_1(uint32_t* seed)
-{
-    return ((float)xorshift32(seed)) / ((float)UINT32_MAX);
-    /* 
-	uint32_t x = *seed;
-	x ^= x << 13;
-	x ^= x >> 17;
-	x ^= x << 5;
-	return ((float)(*seed = x))/((float) UINT32_MAX);
-	*/
-    // previously:
-    // ((float)rand_r(seed) / (float)RAND_MAX)
-    // and before that: rand, but it wasn't thread-safe.
-    // See: <https://stackoverflow.com/questions/43151361/how-to-create-thread-safe-random-number-generator-in-c-using-rand-r> for why to use rand_r:
-    // rand() is not thread-safe, as it relies on (shared) hidden seed.
-}
-
-float rand_float(float max, uint32_t* seed)
-{
-    return rand_0_to_1(seed) * max;
-}
-
-float ur_normal(uint32_t* seed)
-{
-    float u1 = rand_0_to_1(seed);
-    float u2 = rand_0_to_1(seed);
-    float z = sqrtf(-2.0 * log(u1)) * sin(2 * PI * u2);
-    return z;
-}
-
-float random_uniform(float from, float to, uint32_t* seed)
-{
-    return rand_0_to_1(seed) * (to - from) + from;
-}
-
-float random_normal(float mean, float sigma, uint32_t* seed)
-{
-    return (mean + sigma * ur_normal(seed));
-}
-
-float random_lognormal(float logmean, float logsigma, uint32_t* seed)
-{
-    return expf(random_normal(logmean, logsigma, seed));
-}
-
-float random_to(float low, float high, uint32_t* seed)
-{
-    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, seed);
-}
-
-// Mixture function
-
-float mixture(float (*samplers[])(uint32_t*), float* weights, int n_dists, uint32_t* seed)
-{
-
-    // You can see a slightly simpler version of this function in the git history
-    // or in alt/C-02-better-algorithm-one-thread/
-    float sum_weights = array_sum(weights, n_dists);
-    float* cumsummed_normalized_weights = malloc(n_dists * sizeof(float));
-    cumsummed_normalized_weights[0] = weights[0] / sum_weights;
-    for (int i = 1; i < n_dists; i++) {
-        cumsummed_normalized_weights[i] = cumsummed_normalized_weights[i - 1] + weights[i] / sum_weights;
-    }
-
-    //create var holders
-    float p1, result;
-    int sample_index, i, own_length;
-    p1 = random_uniform(0, 1, seed);
-    for (int i = 0; i < n_dists; i++) {
-        if (p1 < cumsummed_normalized_weights[i]) {
-            result = samplers[i](seed);
-            break;
-        }
-    }
-    free(cumsummed_normalized_weights);
-    return result;
-}
-
-// Parallization function
-void paralellize(float (*sampler)(uint32_t* seed), float** results, int n_threads){
-
-    int sample_index, i, split_array_length;
-    uint32_t** seeds = malloc(n_threads * sizeof(uint32_t*));
-    for (uint32_t i = 0; i < n_threads; i++) {
-        seeds[i] = malloc(sizeof(uint32_t));
-        *seeds[i] = i + 1; // xorshift can't start with 0
-    }
-
-    #pragma omp parallel private(i, sample_index, split_array_length)
-    {
-        #pragma omp for
-        for (i = 0; i < n_threads; i++) {
-            split_array_length = split_array_get_length(i, N, n_threads);
-            for (int j = 0; j < split_array_length; j++) {
-                results[i][j] = sampler(seeds[i]);
-            }
-        }
-    }
-
-    for (uint32_t i = 0; i < n_threads; i++) {
-        free(seeds[i]);
-    }
-    free(seeds);
-}
-
-// Functions used for the BOTEC.
-// Their type has to be the same, as we will be passing them around.
-
-float sample_0(uint32_t* seed)
-{
-    return 0;
-}
-
-float sample_1(uint32_t* seed)
-{
-    return 1;
-}
-
-float sample_few(uint32_t* seed)
-{
-    return random_to(1, 3, seed);
-}
-
-float sample_many(uint32_t* seed)
-{
-    return random_to(2, 10, seed);
-}
-
-float sample_mixture(uint32_t* seed){
-    float p_a, p_b, p_c;
-
-    // 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[])(uint32_t*) = { sample_0, sample_1, sample_few, sample_many };
-
-    return mixture(samplers, weights, n_dists, seed);
-}
-
-int main()
-{
-    int n_threads = omp_get_max_threads();
-    // printf("Max threads: %d\n", n_threads);
-    // omp_set_num_threads(n_threads);
-    float** split_array_results = malloc(n_threads * sizeof(float*));
-    split_array_allocate(split_array_results, N, n_threads);
-
-    paralellize(sample_mixture, split_array_results, n_threads);
-    printf("Sum(split_array_results, N)/N = %f\n", split_array_sum(split_array_results, N, n_threads) / N);
-
-    split_array_free(split_array_results, n_threads);
-    return 0;
-}

C/samples.c

@@ -1,7 +1,7 @@
-#include <math.h>
 #include <omp.h>
-#include <stdint.h>
+#include <math.h>
 #include <stdio.h>
+#include <stdint.h>
 #include <stdlib.h>
 
 const float PI = 3.14159265358979323846;
@@ -64,8 +64,7 @@ float split_array_sum(float** meta_array, int length, int divided_into)
     int i;
     float output = 0;
 
-#pragma omp parallel for reduction(+ \
+    #pragma omp parallel for reduction(+:output)
-                                   : output)
 		for (int i = 0; i < divided_into; i++) {
 				float own_partial_sum = 0;
 				int split_array_length = split_array_get_length(i, length, divided_into);
@@ -75,6 +74,7 @@ float split_array_sum(float** meta_array, int length, int divided_into)
 				output += own_partial_sum;
 		}
 		return output;
+
 }
 
 // Pseudo Random number generator
@@ -95,9 +95,8 @@ uint32_t xorshift32(uint32_t* seed)
 
 // Distribution & sampling functions
 
-float rand_0_to_1(uint32_t* seed)
+float rand_0_to_1(uint32_t* seed){
-{
+	return ((float) xorshift32(seed)) / ((float) UINT32_MAX);
-    return ((float)xorshift32(seed)) / ((float)UINT32_MAX);
 	/* 
 	uint32_t x = *seed;
 	x ^= x << 13;
@@ -154,12 +153,12 @@ float random_to(float low, float high, uint32_t* seed)
 void mixture(float (*samplers[])(uint32_t*), float* weights, int n_dists, float** results, int n_threads)
 {
     // You can see a simpler version of this function in the git history
-    // or in alt/C-02-better-algorithm-one-thread/
+    // or in C-02-better-algorithm-one-thread/
     float sum_weights = array_sum(weights, n_dists);
 		float* cumsummed_normalized_weights = malloc(n_dists * sizeof(float));
-    cumsummed_normalized_weights[0] = weights[0] / sum_weights;
+		cumsummed_normalized_weights[0] = weights[0]/sum_weights;
     for (int i = 1; i < n_dists; i++) {
-        cumsummed_normalized_weights[i] = cumsummed_normalized_weights[i - 1] + weights[i] / sum_weights;
+        cumsummed_normalized_weights[i] = cumsummed_normalized_weights[i - 1] + weights[i]/sum_weights;
     }
 
     //create var holders
@@ -173,9 +172,9 @@ void mixture(float (*samplers[])(uint32_t*), float* weights, int n_dists, float*
         *seeds[i] = i + 1; // xorshift can't start with 0
     }
 
-#pragma omp parallel private(i, p1, sample_index, split_array_length)
+    #pragma omp parallel private(i, p1, sample_index, split_array_length)
     {
-#pragma omp for
+        #pragma omp for
         for (i = 0; i < n_threads; i++) {
             split_array_length = split_array_get_length(i, N, n_threads);
             for (int j = 0; j < split_array_length; j++) {

README.md

@@ -133,7 +133,7 @@ The beautiful thing about bc is that it's an arbitrary precision calculator:
 - it's not going to get floating point overflows, unlike practically everything else. Try `1000000001.0 ** 1000000.0` in OCaml, and you will get infinity, try p(1000000000.0, 1000000.0) and you will get a large power of 10 in bc.
 - you can always trade get more precision (at the cost of longer running times). Could be useful if you were working with tricky long tails.
 
-I decided to go with [Gavin Howard's bc](https://git.gavinhoward.com/gavin/bc), because I've been following the guy some time, and I respect him. It also had some crucial extensions, like a random number generator and allowing specifying functions and variables with names longer than one letter.
+I decided to go with [Gavin Howard's bc](https://git.gavinhoward.com/gavin/bc), because I've been following the guy some time, and I respect him. It also had some crucial extensions, like a random number generator and 
 
 ### Overall thoughts