280 lines
10 KiB
C
280 lines
10 KiB
C
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#include <stdbool.h>
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#include <stdint.h>
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#include <stdio.h>
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#include <Windows.h>
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#include "pap2_stdlib.h"
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#include "pap2_stdlib.c"
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#include <math.h>
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typedef float f32;
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typedef double f64;
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static f64 Square(f64 A)
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{
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f64 Result = (A*A);
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return Result;
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}
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static f64 RadiansFromDegrees(f64 Degrees)
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{
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f64 Result = 0.01745329251994329577 * Degrees;
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return Result;
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}
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// NOTE(casey): EarthRadius is generally expected to be 6372.8
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static f64 ReferenceHaversine(f64 X0, f64 Y0, f64 X1, f64 Y1, f64 EarthRadius)
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{
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/* NOTE(casey): This is not meant to be a "good" way to calculate the Haversine distance.
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Instead, it attempts to follow, as closely as possible, the formula used in the real-world
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question on which these homework exercises are loosely based.
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*/
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f64 lat1 = Y0;
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f64 lat2 = Y1;
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f64 lon1 = X0;
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f64 lon2 = X1;
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f64 dLat = RadiansFromDegrees(lat2 - lat1);
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f64 dLon = RadiansFromDegrees(lon2 - lon1);
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lat1 = RadiansFromDegrees(lat1);
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lat2 = RadiansFromDegrees(lat2);
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f64 a = Square(sin(dLat/2.0)) + cos(lat1)*cos(lat2)*Square(sin(dLon/2));
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f64 c = 2.0*asin(sqrt(a));
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f64 Result = EarthRadius * c;
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return Result;
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}
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bool PAP_CharIsWhiteSpace(char ch)
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{
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bool result = ch == ' ' || ch == '\n' || ch == '\r' || ch == '\t';
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return result;
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}
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typedef struct PAP_Str8ToU64Result {
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bool success;
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uint64_t value;
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} PAP_Str8ToU64Result;
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PAP_Str8ToU64Result PAP_Str8_ToU64(PAP_Str8 string)
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{
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PAP_Str8ToU64Result result = {0};
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size_t ch_index = 0;
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while (ch_index < string.size && PAP_CharIsWhiteSpace(string.data[ch_index]))
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ch_index++;
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for (; ch_index < string.size; ch_index++) {
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char ch = string.data[ch_index];
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if (ch >= '0' && ch <= '9') {
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result.value = (result.value * 10) + (ch - '0');
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} else {
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return result;
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}
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}
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result.success = true;
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return result;
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}
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// NOTE: PCG RNG from Demetri Spanos: https://github.com/demetri/scribbles
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// pcg32_pie, based on the minimal C version from O'Neill at pcg-random.org;
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// I've made a few (subjective) UX improvements for beginner use
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//
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// I'm not allowing the user to pick the stream/increment constant at all,
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// since there is almost never a reason for doing this in common applications.
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// This means that the prng state is reduced to a single uint64_t which also
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// means we can avoid having a state struct at all. The (fixed) stream constant
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// uses the leading hex digits of pi and e multipled by 2^30 (c90fdaa2 and
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// adf85459).
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//
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// I have also added an XOR with the same digits on the output path prior
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// to xorshift mixing. This prevents the "surprising" result that the
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// first "random 32-bit number" from a (very common) 0 seed is 0.
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//
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// use:
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// uint64_t state = 12345; // whatever you like can go here
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// uint32_t some_random_32_bits = pcg32_pie(&state);
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// uint32_t more_random_32_bits = pcg32_pie(&state);
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#pragma warning(push)
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#pragma warning(disable: 4146) // warning C4146: unary minus operator applied to unsigned type, result still unsigned
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uint32_t PAP_PCG32_Pie (uint64_t *state)
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{
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uint64_t old = *state ^ 0xc90fdaa2adf85459ULL;
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*state = *state * 6364136223846793005ULL + 0xc90fdaa2adf85459ULL;
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uint32_t xorshifted = (uint32_t)(((old >> 18u) ^ old) >> 27u);
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uint32_t rot = old >> 59u;
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return (xorshifted >> rot) | (xorshifted << ((-rot) & 31));
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}
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#pragma warning(pop)
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f64 PAP_PCG32_PieF64(uint64_t *state, f64 min, f64 max)
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{
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uint32_t u32_value = PAP_PCG32_Pie(state);
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f64 t01 = PAP_CAST(f64)u32_value / PAP_CAST(f64)PAP_CAST(uint32_t)-1;
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f64 result = min + (max - min) * t01;
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return result;
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}
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#define PRINT_USAGE PAP_PrintLnFmt("Usage: %s [uniform/cluster] [random seed] [number of coordinate pairs to generate]", argv[0])
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int main(int argc, char **argv)
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{
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// NOTE: Unit Tests
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// =========================================================================
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{
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{
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PAP_Str8ToU64Result result = PAP_Str8_ToU64(PAP_STR8("00"));
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PAP_ASSERT(result.success);
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PAP_ASSERT(result.value == 0);
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}
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{
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PAP_Str8ToU64Result result = PAP_Str8_ToU64(PAP_STR8("+100"));
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PAP_ASSERT(!result.success);
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}
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{
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PAP_Str8ToU64Result result = PAP_Str8_ToU64(PAP_STR8("100,0"));
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PAP_ASSERT(!result.success);
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}
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{
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PAP_Str8ToU64Result result = PAP_Str8_ToU64(PAP_STR8("100a"));
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PAP_ASSERT(!result.success);
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}
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{
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PAP_Str8ToU64Result result = PAP_Str8_ToU64(PAP_STR8("3147"));
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PAP_ASSERT(result.success);
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PAP_ASSERT(result.value == 3147);
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}
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}
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// NOTE: Arg Parsing
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// =========================================================================
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if (argc != 4) {
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PRINT_USAGE;
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return -1;
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}
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PAP_Str8 arg_uniform_cluster = {argv[1], strlen(argv[1])};
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PAP_Str8 arg_random_seed = {argv[2], strlen(argv[2])};
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PAP_Str8 arg_number_of_coordinate_pairs_to_generate = {argv[3], strlen(argv[3])};
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typedef enum PointGenerator {
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PointGenerator_Invalid,
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PointGenerator_Uniform,
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PointGenerator_Cluster,
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} PointGenerator;
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PAP_Str8ToU64Result random_seed_u64_result = PAP_Str8_ToU64(arg_random_seed);
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PAP_Str8ToU64Result number_of_coordinate_pairs_to_generate_u64_result = PAP_Str8_ToU64(arg_number_of_coordinate_pairs_to_generate);
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PointGenerator point_generator = PointGenerator_Invalid;
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if (PAP_Str8_Equals(arg_uniform_cluster, PAP_STR8("uniform"))) {
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point_generator = PointGenerator_Uniform;
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} else if (PAP_Str8_Equals(arg_uniform_cluster, PAP_STR8("cluster"))) {
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point_generator = PointGenerator_Cluster;
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} else {
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PRINT_USAGE;
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return -1;
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}
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if (!random_seed_u64_result.success) {
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PAP_PrintLnFmt("Random seed was not a valid U64 value [seed=%.*s]", PAP_STR8_FMT(arg_random_seed));
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PRINT_USAGE;
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return -1;
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}
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if (!number_of_coordinate_pairs_to_generate_u64_result.success) {
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PAP_PrintLnFmt("Number of coordinate pairs to generate was not a valid U64 value [seed=%.*s]", PAP_STR8_FMT(arg_number_of_coordinate_pairs_to_generate));
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PRINT_USAGE;
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return -1;
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}
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uint32_t const MAX_COORD_PAIRS = 100'000'000;
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if (number_of_coordinate_pairs_to_generate_u64_result.value > MAX_COORD_PAIRS) {
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PAP_PrintLnFmt("Maximum number of coordinate pairs exceeded, exiting to avoid accidental large files [requested=%zu, max=%zu]",
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number_of_coordinate_pairs_to_generate_u64_result.value,
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MAX_COORD_PAIRS);
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PRINT_USAGE;
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return -1;
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}
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// NOTE: Generator
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// =========================================================================
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uint64_t point_count = number_of_coordinate_pairs_to_generate_u64_result.value;
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uint64_t random_seed = random_seed_u64_result.value;
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uint64_t rng_state = random_seed;
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HANDLE haversine_json_file_handle = CreateFile(
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/*LPCSTR lpFileName*/ "haversine.json",
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/*DWORD dwDesiredAccess*/ GENERIC_WRITE,
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/*DWORD dwShareMode*/ 0,
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/*LPSECURITY_ATTRIBUTES lpSecurityAttributes*/ NULL,
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/*DWORD dwCreationDisposition*/ CREATE_ALWAYS,
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/*DWORD dwFlagsAndAttributes*/ 0,
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/*HANDLE hTemplateFile*/ NULL
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);
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HANDLE haversine_f64_file_handle = CreateFile(
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/*LPCSTR lpFileName*/ "haversine.f64",
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/*DWORD dwDesiredAccess*/ GENERIC_WRITE,
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/*DWORD dwShareMode*/ 0,
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/*LPSECURITY_ATTRIBUTES lpSecurityAttributes*/ NULL,
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/*DWORD dwCreationDisposition*/ CREATE_ALWAYS,
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/*DWORD dwFlagsAndAttributes*/ 0,
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/*HANDLE hTemplateFile*/ NULL
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);
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f64 const LAT_LON_MIN = -180.0;
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f64 const LAT_LON_MAX = 180.0;
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uint64_t const MAX_CLUSTERS = 64;
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uint64_t const points_per_cluster = point_count / MAX_CLUSTERS;
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char tmp_buffer[128];
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f64 expected_sum = 0;
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PAP_PrintHandle(haversine_json_file_handle, PAP_STR8("{\"pairs\":[\n"));
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f64 const sum_coefficient = 1.0 / point_count;
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f64 point_centre = 0;
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f64 point_min_offset = LAT_LON_MIN;
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f64 point_max_offset = LAT_LON_MAX;
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for (int index = 0; index < point_count; index++) {
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if (point_generator == PointGenerator_Cluster && (index % points_per_cluster) == 0) {
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point_centre = PAP_PCG32_PieF64(&rng_state, LAT_LON_MIN, LAT_LON_MAX);
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point_min_offset = -PAP_PCG32_PieF64(&rng_state, 0, 45);
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point_max_offset = -point_min_offset;
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}
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f64 x0 = point_centre + PAP_PCG32_PieF64(&rng_state, point_min_offset, point_max_offset);
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f64 y0 = point_centre + PAP_PCG32_PieF64(&rng_state, point_min_offset, point_max_offset);
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f64 x1 = point_centre + PAP_PCG32_PieF64(&rng_state, point_min_offset, point_max_offset);
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f64 y1 = point_centre + PAP_PCG32_PieF64(&rng_state, point_min_offset, point_max_offset);
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f64 haversine_dist = ReferenceHaversine(x0, y0, x1, y1, /*EarthRadius*/ 6372.8);
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PAP_PrintHandle(haversine_f64_file_handle, (PAP_Str8){.data = (char *)&haversine_dist, .size = sizeof(haversine_dist)});
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expected_sum += (sum_coefficient * haversine_dist);
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size_t json_line_size = snprintf(tmp_buffer, sizeof(tmp_buffer), " {\"x0\": %f, \"y0\": %f, \"x1\": %f, \"y1\": %f}%s\n", x0, y0, x1, y1, (index == (point_count - 1) ? "" : ","));
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PAP_ASSERT(json_line_size < sizeof(tmp_buffer));
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PAP_PrintHandle(haversine_json_file_handle, (PAP_Str8){.data = tmp_buffer, .size = json_line_size});
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}
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PAP_PrintHandle(haversine_json_file_handle, PAP_STR8("]}\n"));
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PAP_PrintHandle(haversine_f64_file_handle, (PAP_Str8){.data = (char *)&expected_sum, .size = sizeof(expected_sum)});
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CloseHandle(haversine_json_file_handle);
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CloseHandle(haversine_f64_file_handle);
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PAP_PrintLnFmt("Method: %s", (point_generator == PointGenerator_Uniform ? "uniform" : "cluster"));
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PAP_PrintLnFmt("Seed: %zu", random_seed);
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PAP_PrintLnFmt("Pair Count: %zu", point_count);
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PAP_PrintLnFmt("Expected Sum: %f", expected_sum);
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return 0;
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}
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