Add sieve exercise (#109)

Author: keiravillekode

config.json

@@ -282,6 +282,14 @@
         "prerequisites": [],
         "difficulty": 5
       },
+      {
+        "slug": "sieve",
+        "name": "Sieve",
+        "uuid": "4ca13a1c-d296-4b5c-b5f7-7242b2b8f54b",
+        "practices": [],
+        "prerequisites": [],
+        "difficulty": 5
+      },
       {
         "slug": "knapsack",
         "name": "Knapsack",

exercises/practice/sieve/.docs/instructions.md

@@ -0,0 +1,42 @@
+# Instructions
+
+Your task is to create a program that implements the Sieve of Eratosthenes algorithm to find all prime numbers less than or equal to a given number.
+
+A prime number is a number larger than 1 that is only divisible by 1 and itself.
+For example, 2, 3, 5, 7, 11, and 13 are prime numbers.
+By contrast, 6 is _not_ a prime number as it not only divisible by 1 and itself, but also by 2 and 3.
+
+To use the Sieve of Eratosthenes, you first create a list of all the numbers between 2 and your given number.
+Then you repeat the following steps:
+
+1. Find the next unmarked number in your list (skipping over marked numbers).
+   This is a prime number.
+2. Mark all the multiples of that prime number as **not** prime.
+
+You keep repeating these steps until you've gone through every number in your list.
+At the end, all the unmarked numbers are prime.
+
+~~~~exercism/note
+The tests don't check that you've implemented the algorithm, only that you've come up with the correct list of primes.
+To check you are implementing the Sieve correctly, a good first test is to check that you do not use division or remainder operations.
+~~~~
+
+## Example
+
+Let's say you're finding the primes less than or equal to 10.
+
+- List out 2, 3, 4, 5, 6, 7, 8, 9, 10, leaving them all unmarked.
+- 2 is unmarked and is therefore a prime.
+  Mark 4, 6, 8 and 10 as "not prime".
+- 3 is unmarked and is therefore a prime.
+  Mark 6 and 9 as not prime _(marking 6 is optional - as it's already been marked)_.
+- 4 is marked as "not prime", so we skip over it.
+- 5 is unmarked and is therefore a prime.
+  Mark 10 as not prime _(optional - as it's already been marked)_.
+- 6 is marked as "not prime", so we skip over it.
+- 7 is unmarked and is therefore a prime.
+- 8 is marked as "not prime", so we skip over it.
+- 9 is marked as "not prime", so we skip over it.
+- 10 is marked as "not prime", so we stop as there are no more numbers to check.
+
+You've examined all numbers and found 2, 3, 5, and 7 are still unmarked, which means they're the primes less than or equal to 10.

exercises/practice/sieve/.docs/introduction.md

@@ -0,0 +1,7 @@
+# Introduction
+
+You bought a big box of random computer parts at a garage sale.
+You've started putting the parts together to build custom computers.
+
+You want to test the performance of different combinations of parts, and decide to create your own benchmarking program to see how your computers compare.
+You choose the famous "Sieve of Eratosthenes" algorithm, an ancient algorithm, but one that should push your computers to the limits.

exercises/practice/sieve/.meta/config.json

@@ -0,0 +1,19 @@
+{
+  "authors": [
+    "keiravillekode"
+  ],
+  "files": {
+    "solution": [
+      "sieve.s"
+    ],
+    "test": [
+      "sieve_test.c"
+    ],
+    "example": [
+      ".meta/example.s"
+    ]
+  },
+  "blurb": "Use the Sieve of Eratosthenes to find all the primes from 2 up to a given number.",
+  "source": "Sieve of Eratosthenes at Wikipedia",
+  "source_url": "https://en.wikipedia.org/wiki/Sieve_of_Eratosthenes"
+}

exercises/practice/sieve/.meta/example.s

@@ -0,0 +1,44 @@
+.text
+.globl sieve
+
+/* extern size_t sieve(uint64_t* primes, uint64_t limit); */
+sieve:
+        add     x2, x1, #16
+        and     x2, x2, #-16            /* limit, rounded up to the next multiple of 16 */
+        mov     x3, sp
+        sub     sp, sp, x2              /* allocate space on stack */
+        mov     x4, #-1
+        mov     x5, sp
+
+.fill:
+        stp     x4, x4, [x3, #-16]!     /* store pair, pre-decrement */
+        cmp     x3, x5
+        bne     .fill
+
+        mov     x3, x0                  /* output pointer */
+        mov     x4, #1
+
+.search:
+        add     x4, x4, #1              /* candidate prime */
+        cmp     x1, x4
+        blo     .exit                   /* unsigned < */
+
+        ldrb    w5, [sp, x4]
+        cbz     w5, .search             /* if composite, move on to next candidate */
+
+        str     x4, [x3], #8
+        mul     x5, x4, x4              /* multiple of prime */
+
+.mark:
+        cmp     x1, x5
+        blo     .search                 /* unsigned < */
+
+        strb    wzr, [sp, x5]           /* mark as composite */
+        add     x5, x5, x4
+        b       .mark
+
+.exit:
+        sub     x0, x3, x0
+        lsr     x0, x0, #3              /* number of primes */
+        add     sp, sp, x2              /* restore original stack pointer */ 
+        ret

exercises/practice/sieve/.meta/tests.toml

@@ -0,0 +1,25 @@
+# This is an auto-generated file.
+#
+# Regenerating this file via `configlet sync` will:
+# - Recreate every `description` key/value pair
+# - Recreate every `reimplements` key/value pair, where they exist in problem-specifications
+# - Remove any `include = true` key/value pair (an omitted `include` key implies inclusion)
+# - Preserve any other key/value pair
+#
+# As user-added comments (using the # character) will be removed when this file
+# is regenerated, comments can be added via a `comment` key.
+
+[88529125-c4ce-43cc-bb36-1eb4ddd7b44f]
+description = "no primes under two"
+
+[4afe9474-c705-4477-9923-840e1024cc2b]
+description = "find first prime"
+
+[974945d8-8cd9-4f00-9463-7d813c7f17b7]
+description = "find primes up to 10"
+
+[2e2417b7-3f3a-452a-8594-b9af08af6d82]
+description = "limit is prime"
+
+[92102a05-4c7c-47de-9ed0-b7d5fcd00f21]
+description = "find primes up to 1000"

exercises/practice/sieve/Makefile

@@ -0,0 +1,36 @@
+AS = aarch64-linux-gnu-as
+CC = aarch64-linux-gnu-gcc
+
+CFLAGS = -g -Wall -Wextra -pedantic -Werror
+LDFLAGS =
+
+ALL_LDFLAGS = -pie -Wl,--fatal-warnings
+
+ALL_CFLAGS = -std=c99 -fPIE $(CFLAGS)
+ALL_LDFLAGS += $(LDFLAGS)
+
+C_OBJS = $(patsubst %.c,%.o,$(wildcard *.c))
+AS_OBJS = $(patsubst %.s,%.o,$(wildcard *.s))
+ALL_OBJS = $(filter-out example.o,$(C_OBJS) $(AS_OBJS) vendor/unity.o)
+
+CC_CMD = $(CC) $(ALL_CFLAGS) -c -o $@ $<
+
+all: tests
+	qemu-aarch64 -L /usr/aarch64-linux-gnu ./$<
+
+tests: $(ALL_OBJS)
+	@$(CC) $(ALL_CFLAGS) $(ALL_LDFLAGS) -o $@ $(ALL_OBJS)
+
+%.o: %.s
+	@$(AS) -o $@ $<
+
+%.o: %.c
+	@$(CC_CMD)
+
+vendor/unity.o: vendor/unity.c vendor/unity.h vendor/unity_internals.h
+	@$(CC_CMD)
+
+clean:
+	@rm -f *.o vendor/*.o tests
+
+.PHONY: all clean

exercises/practice/sieve/sieve.s

@@ -0,0 +1,5 @@
+.text
+.globl sieve
+
+sieve:
+    ret

exercises/practice/sieve/sieve_test.c

@@ -0,0 +1,67 @@
+#include "vendor/unity.h"
+
+#include <stddef.h>
+#include <stdint.h>
+
+#define MAX_ARRAY_SIZE 200
+#define ARRAY_SIZE(x) (sizeof(x) / sizeof((x)[0]))
+
+extern size_t sieve(uint64_t* primes, uint64_t limit);
+
+void setUp(void) {
+}
+
+void tearDown(void) {
+}
+
+void test_no_primes_under_two(void) {
+    uint64_t actual[MAX_ARRAY_SIZE];
+    const size_t size = sieve(actual, 1);
+    TEST_ASSERT_EQUAL_UINT(0U, size);
+}
+
+void test_find_first_prime(void) {
+    TEST_IGNORE();
+    const uint64_t expected[] = {2};
+    uint64_t actual[MAX_ARRAY_SIZE];
+    const size_t size = sieve(actual, 2);
+    TEST_ASSERT_EQUAL_UINT(ARRAY_SIZE(expected), size);
+    TEST_ASSERT_EQUAL_UINT64_ARRAY(expected, actual, size);
+}
+
+void test_find_primes_up_to_10(void) {
+    TEST_IGNORE();
+    const uint64_t expected[] = {2, 3, 5, 7};
+    uint64_t actual[MAX_ARRAY_SIZE];
+    const size_t size = sieve(actual, 10);
+    TEST_ASSERT_EQUAL_UINT(ARRAY_SIZE(expected), size);
+    TEST_ASSERT_EQUAL_UINT64_ARRAY(expected, actual, size);
+}
+
+void test_limit_is_prime(void) {
+    TEST_IGNORE();
+    const uint64_t expected[] = {2, 3, 5, 7, 11, 13};
+    uint64_t actual[MAX_ARRAY_SIZE];
+    const size_t size = sieve(actual, 13);
+    TEST_ASSERT_EQUAL_UINT(ARRAY_SIZE(expected), size);
+    TEST_ASSERT_EQUAL_UINT64_ARRAY(expected, actual, size);
+}
+
+void test_find_primes_up_to_1000(void) {
+    TEST_IGNORE();
+    const uint64_t expected[] = {2, 3, 5, 7, 11, 13, 17, 19, 23, 29, 31, 37, 41, 43, 47, 53, 59, 61, 67, 71, 73, 79, 83, 89, 97, 101, 103, 107, 109, 113, 127, 131, 137, 139, 149, 151, 157, 163, 167, 173, 179, 181, 191, 193, 197, 199, 211, 223, 227, 229, 233, 239, 241, 251, 257, 263, 269, 271, 277, 281, 283, 293, 307, 311, 313, 317, 331, 337, 347, 349, 353, 359, 367, 373, 379, 383, 389, 397, 401, 409, 419, 421, 431, 433, 439, 443, 449, 457, 461, 463, 467, 479, 487, 491, 499, 503, 509, 521, 523, 541, 547, 557, 563, 569, 571, 577, 587, 593, 599, 601, 607, 613, 617, 619, 631, 641, 643, 647, 653, 659, 661, 673, 677, 683, 691, 701, 709, 719, 727, 733, 739, 743, 751, 757, 761, 769, 773, 787, 797, 809, 811, 821, 823, 827, 829, 839, 853, 857, 859, 863, 877, 881, 883, 887, 907, 911, 919, 929, 937, 941, 947, 953, 967, 971, 977, 983, 991, 997};
+    uint64_t actual[MAX_ARRAY_SIZE];
+    const size_t size = sieve(actual, 1000);
+    TEST_ASSERT_EQUAL_UINT(ARRAY_SIZE(expected), size);
+    TEST_ASSERT_EQUAL_UINT64_ARRAY(expected, actual, size);
+}
+
+int main(void) {
+    UNITY_BEGIN();
+    RUN_TEST(test_no_primes_under_two);
+    RUN_TEST(test_find_first_prime);
+    RUN_TEST(test_find_primes_up_to_10);
+    RUN_TEST(test_limit_is_prime);
+    RUN_TEST(test_find_primes_up_to_1000);
+    return UNITY_END();
+}