Switch to C, stop using OpenMP, start using GMP.

.gitlab-ci.yml

@@ -2,12 +2,19 @@ image: gcc
 
 build:
     stage: build
+    # Install dependencies
     before_script:
-        - apt update && apt -y install cmake libgomp1 libgmp-dev
+        - apt update && apt -y install cmake libgmp-dev
+    # Build the project
     script:
         - cd build/
         - cmake -DCMAKE_BUILD_TYPE=Release ..
         - make
+    # Find the resulting binary
     artifacts:
         paths:
             - build/indivisible
+    # Cache .o files for faster compiling
+    cache:
+        paths:
+            - "*.o"

CMakeLists.txt

@@ -13,20 +13,21 @@ set(CMAKE_MODULE_PATH
 	${CMAKE_MODULE_PATH}
 	${CMAKE_SOURCE_DIR}/cmake/)
 
-find_package(OpenMP REQUIRED)
 find_package(GMP REQUIRED)
 
 include_directories(
 	${GMP_INCLUDE_DIR})
 
 set(SRCS
-    src/Main.cpp)
+	src/main.c
+	src/list.c)
 
-set(CMAKE_CXX_FLAGS "-std=c++11 ${OpenMP_CXX_FLAGS} -fno-elide-constructors -pedantic-errors -Wall -Wextra -Werror -Wpedantic -Winit-self -Wmissing-declarations -Wuninitialized -Wfatal-errors")
-set(CMAKE_CXX_FLAGS_RELEASE "-O3")
-set(CMAKE_CXX_FLAGS_DEBUG "-g -O0")
-set(CMAKE_CXX_FLAGS_RELWITHDEBINFO "-g -O3")
-set(CMAKE_CXX_FLAGS_MINSIZEREL "-Os")
+# Define the C flags.
+set(CMAKE_C_FLAGS "-std=gnu99 -Wall -Wextra -Werror -Wfatal-errors -Wmissing-declarations -pedantic-errors")
+set(CMAKE_C_FLAGS_DEBUG "${CMAKE_C_FLAGS} -g -O0")
+set(CMAKE_C_FLAGS_RELEASE "${CMAKE_C_FLAGS} -O3")
+set(CMAKE_C_FLAGS_RELWITHDEBINFO "${CMAKE_C_FLAGS} -g -O3")
+set(CMAKE_C_FLAGS_MINSIZEREL "${CMAKE_C_FLAGS} -Os")
 
 if(NOT CMAKE_BUILD_TYPE MATCHES Debug AND NOT CMAKE_BUILD_TYPE MATCHES RelWithDebInfo)
 	add_definitions(-DNDEBUG)

README.md

@@ -2,12 +2,15 @@ Indivisible
 ===========
 [![build status](https://gitlab.com/Deathsbreed/Indivisible/badges/master/build.svg)](https://gitlab.com/Deathsbreed/Indivisible/commits/master)
 
-Indivisible is an optimized prime number generator written in C++.
+Indivisible is an optimized prime number generator written in C.
 
 Building
 --------
-This project uses CMake to build and depends on OpenMP.
+There are multiple dependencies to install before compiling the project:
+- CMake
+- GMP
 
+Once the dependencies are installed you can compile by running the following from the root directory of the project:
 ```bash
 $ cd build/
 $ cmake ..

src/Main.cpp

@@ -1,52 +0,0 @@
-#include <iostream>
-#include <omp.h>
-#include <vector>
-#include <csignal>
-#include <cassert>
-
-static bool run;
-
-int main(void) {
-	std::cout << "Indivisible v0.1\n";
-	run = true;
-
-	signal(SIGINT, [](int signum) {
-			std::cout << "Exiting (" << signum << ")\n";
-			run = false;
-			});
-
-	std::vector<unsigned long long> primes;
-	primes.push_back(2);
-	unsigned long long num = 3;
-
-	// Use for to accomodate for OpenMP
-	#pragma omp parallel
-	{
-		do {
-			unsigned long long myNum;
-			#pragma omp critical
-			{
-				myNum = num;
-				num += 2;
-			}
-			bool isPrime = true;
-			#pragma omp barrier
-			for(auto i : primes) {
-				if(i > myNum / 2) break;
-				if(myNum % i == 0) {
-					isPrime = false;
-					break;
-				}
-			}
-			if(isPrime) {
-				#pragma omp critical
-				{
-					primes.push_back(num);
-					std::cout << num << std::endl;
-				}
-			}
-		} while(run);
-	}
-
-	return 0;
-}

src/list.c

@@ -0,0 +1,44 @@
+#include "list.h"
+#include <stdlib.h>
+#include <stdio.h>
+
+#include "optimizers.h"
+
+/**
+ * This is the number of elements by which the list expands.
+ * WARNING: Always use doubles for this number (2^X)
+ */
+#define BLOCK_SIZE 1024
+
+void initList(List *l) {
+	l->list = malloc(sizeof(mpz_t) * BLOCK_SIZE);
+	if(!l->list) {
+		fprintf(stderr, "Failed to allocate memory to list!\n");
+		exit(1);
+	}
+	l->size = BLOCK_SIZE;
+	l->end = 0;
+}
+
+void deInitList(List *l) {
+	free(l->list);
+}
+
+void addToList(List *l, mpz_t n) {
+	if(l->end == l->size) {
+		l->size += BLOCK_SIZE;
+		if(unlikely(l->size == 0)) {
+			fprintf(stderr,
+					"size has reached limit of `long long int' type!\n");
+			exit(1);
+		}
+		void *tmp = realloc(l->list, sizeof(mpz_t) * l->size);
+		if(!tmp) {
+			fprintf(stderr, "Failed to allocate more memory to list!\n");
+			exit(1);
+		}
+		l->list = (mpz_t*)tmp;
+	}
+	mpz_init(l->list[l->end]);
+	mpz_set(l->list[l->end++], n);
+}

src/list.h

@@ -0,0 +1,36 @@
+#pragma once
+#include <gmp.h>
+#include <stdbool.h>
+
+/**
+ * @brief An infinitely expanding list type.
+ */
+typedef struct {
+	mpz_t *list; //!< The list of elements
+	unsigned long long int size; //!< How many elements are in the list
+	unsigned long long int end; //!< The last element of the list (in use)
+} List;
+
+/**
+ * @brief Initialize a List.
+ * @details Initialize the list and its variables, allocating memory
+ * to the pointer array inside. Returns true on success and false on
+ * failure.
+ * @param[in] l A pointer to a List type to be initialized.
+ */
+void initList(List *l);
+
+/**
+ * @brief Deinitialize a List.
+ * @details Release all memory that has been allocated to the list.
+ * @param[in] l A pointer to a List type to be deinitialized.
+ */
+void deInitList(List *l);
+
+/**
+ * @brief Adds a new item to a List type.
+ * @details Add item `n' at the end of a List type.
+ * @param[out] l List to which the variable should be appended.
+ * @param[in] n variable to be appended to the list.
+ */
+void addToList(List *l, mpz_t n);

src/main.c

@@ -0,0 +1,65 @@
+#include <stdio.h>
+#include <stdlib.h>
+#include <signal.h>
+#include <stdbool.h>
+#include <gmp.h>
+
+#include "list.h"
+
+static bool run;
+void leave();
+
+int main(void) {
+	printf("Indivisible v0.2\n");
+
+	// Quit on ^C by setting `run = false'
+	run = true;
+	signal(SIGINT, leave);
+
+	// Primes we've found
+	List primes;
+	initList(&primes);
+
+	// The number we're going to be testing for
+	mpz_t num;
+	mpz_init(num);
+
+	// Add 2, a known prime to this list
+	mpz_set_ui(num, 2);
+	addToList(&primes, num);
+	if(mpz_out_str(stdout, 10, num) == 0) {
+		fprintf(stderr, "Could not print to `stdout'!\n");
+		exit(1);
+	}
+	printf("\n");
+	mpz_add_ui(num, num, 1);
+
+	do {
+		// Loop through found primes
+		for(unsigned long long int i = 0; i < primes.size; ++i) {
+			// If `num' is divisible by a prime then go to the next number
+			if(mpz_divisible_p(num, primes.list[i]) != 0) goto nextPrime;
+		}
+
+		// `num' is a prime so we add it to the list and print it
+		addToList(&primes, num);
+		if(mpz_out_str(stdout, 10, num) == 0) {
+			fprintf(stderr, "Could not print to `stdout'!\n");
+			exit(1);
+		}
+		printf("\n");
+
+nextPrime:
+		// Add 2 (skip even numbers since they're all divisible by 2)
+		mpz_add_ui(num, num, 2);
+	} while(run);
+
+	// Deinitialize the list
+	deInitList(&primes);
+	return 0;
+}
+
+void leave() {
+	printf("Exiting...\n");
+	run = false;
+}

src/optimizers.h

@@ -0,0 +1,3 @@
+#pragma once
+#define likely(x)    __builtin_expect(!!(x), 1)
+#define unlikely(x)  __builtin_expect(!!(x), 0)