diff --git a/src/tests/vm/parallel-merge.c b/src/tests/vm/parallel-merge.c new file mode 100644 index 0000000000000000000000000000000000000000..cc09bb13a05effb3628bc1ce48f2d4673646b57f --- /dev/null +++ b/src/tests/vm/parallel-merge.c @@ -0,0 +1,149 @@ +/* Generates about 1 MB of random data that is then divided into + 16 chunks. A separate subprocess sorts each chunk; the + subprocesses run in parallel. Then we merge the chunks and + verify that the result is what it should be. */ + +#include "tests/vm/parallel-merge.h" +#include <stdio.h> +#include <syscall.h> +#include "tests/arc4.h" +#include "tests/lib.h" +#include "tests/main.h" + +#define CHUNK_SIZE (128 * 1024) +#define CHUNK_CNT 8 /* Number of chunks. */ +#define DATA_SIZE (CHUNK_CNT * CHUNK_SIZE) /* Buffer size. */ + +unsigned char buf1[DATA_SIZE], buf2[DATA_SIZE]; +size_t histogram[256]; + +/* Initialize buf1 with random data, + then count the number of instances of each value within it. */ +static void +init (void) +{ + struct arc4 arc4; + size_t i; + + msg ("init"); + + arc4_init (&arc4, "foobar", 6); + arc4_crypt (&arc4, buf1, sizeof buf1); + for (i = 0; i < sizeof buf1; i++) + histogram[buf1[i]]++; +} + +/* Sort each chunk of buf1 using SUBPROCESS, + which is expected to return EXIT_STATUS. */ +static void +sort_chunks (const char *subprocess, int exit_status) +{ + pid_t children[CHUNK_CNT]; + size_t i; + + for (i = 0; i < CHUNK_CNT; i++) + { + char fn[128]; + char cmd[128]; + int handle; + + msg ("sort chunk %zu", i); + + /* Write this chunk to a file. */ + snprintf (fn, sizeof fn, "buf%zu", i); + create (fn, CHUNK_SIZE); + quiet = true; + CHECK ((handle = open (fn)) > 1, "open \"%s\"", fn); + write (handle, buf1 + CHUNK_SIZE * i, CHUNK_SIZE); + close (handle); + + /* Sort with subprocess. */ + snprintf (cmd, sizeof cmd, "%s %s", subprocess, fn); + CHECK ((children[i] = exec (cmd)) != -1, "exec \"%s\"", cmd); + quiet = false; + } + + for (i = 0; i < CHUNK_CNT; i++) + { + char fn[128]; + int handle; + + CHECK (wait (children[i]) == exit_status, "wait for child %zu", i); + + /* Read chunk back from file. */ + quiet = true; + snprintf (fn, sizeof fn, "buf%zu", i); + CHECK ((handle = open (fn)) > 1, "open \"%s\"", fn); + read (handle, buf1 + CHUNK_SIZE * i, CHUNK_SIZE); + close (handle); + quiet = false; + } +} + +/* Merge the sorted chunks in buf1 into a fully sorted buf2. */ +static void +merge (void) +{ + unsigned char *mp[CHUNK_CNT]; + size_t mp_left; + unsigned char *op; + size_t i; + + msg ("merge"); + + /* Initialize merge pointers. */ + mp_left = CHUNK_CNT; + for (i = 0; i < CHUNK_CNT; i++) + mp[i] = buf1 + CHUNK_SIZE * i; + + /* Merge. */ + op = buf2; + while (mp_left > 0) + { + /* Find smallest value. */ + size_t min = 0; + for (i = 1; i < mp_left; i++) + if (*mp[i] < *mp[min]) + min = i; + + /* Append value to buf2. */ + *op++ = *mp[min]; + + /* Advance merge pointer. + Delete this chunk from the set if it's emptied. */ + if ((++mp[min] - buf1) % CHUNK_SIZE == 0) + mp[min] = mp[--mp_left]; + } +} + +static void +verify (void) +{ + size_t buf_idx; + size_t hist_idx; + + msg ("verify"); + + buf_idx = 0; + for (hist_idx = 0; hist_idx < sizeof histogram / sizeof *histogram; + hist_idx++) + { + while (histogram[hist_idx]-- > 0) + { + if (buf2[buf_idx] != hist_idx) + fail ("bad value %d in byte %zu", buf2[buf_idx], buf_idx); + buf_idx++; + } + } + + msg ("success, buf_idx=%'zu", buf_idx); +} + +void +parallel_merge (const char *child_name, int exit_status) +{ + init (); + sort_chunks (child_name, exit_status); + merge (); + verify (); +}