aiwork

AI-work/matmult.c

@@ -0,0 +1,151 @@
+#include <stdio.h>
+#include <stdlib.h>
+#include <pthread.h>
+#include <sys/time.h>
+
+#define MAX_THREADS 64
+
+int N;
+double **A, **B, **C_parallel, **C_serial;
+int nthreads;
+int rows_per_thread;
+
+double **allocate_matrix(int n)
+{
+    double **mat = (double **)malloc(n * sizeof(double *));
+    for (int i = 0; i < n; i++) {
+        mat[i] = (double *)malloc(n * sizeof(double));
+    }
+    return mat;
+}
+
+void free_matrix(double **mat, int n)
+{
+    for (int i = 0; i < n; i++) free(mat[i]);
+    free(mat);
+}
+
+void init_matrix(double **mat, int n)
+{
+    for (int i = 0; i < n; i++)
+        for (int j = 0; j < n; j++)
+            mat[i][j] = (double)(rand() % 100) / 10.0;
+}
+
+void *multiply_thread(void *arg)
+{
+    int start_row = *(int *)arg;
+    int end_row = start_row + rows_per_thread;
+    if (end_row > N) end_row = N;
+
+    for (int i = start_row; i < end_row; i++) {
+        for (int j = 0; j < N; j++) {
+            double sum = 0.0;
+            for (int k = 0; k < N; k++) {
+                sum += A[i][k] * B[k][j];
+            }
+            C_parallel[i][j] = sum;
+        }
+    }
+    return NULL;
+}
+
+void serial_multiply()
+{
+    for (int i = 0; i < N; i++) {
+        for (int j = 0; j < N; j++) {
+            double sum = 0.0;
+            for (int k = 0; k < N; k++) {
+                sum += A[i][k] * B[k][j];
+            }
+            C_serial[i][j] = sum;
+        }
+    }
+}
+
+double get_time()
+{
+    struct timeval tv;
+    gettimeofday(&tv, NULL);
+    return tv.tv_sec + tv.tv_usec / 1000000.0;
+}
+
+int verify()
+{
+    for (int i = 0; i < N; i++) {
+        for (int j = 0; j < N; j++) {
+            if (C_parallel[i][j] - C_serial[i][j] > 0.001 ||
+                C_serial[i][j] - C_parallel[i][j] > 0.001) {
+                printf("Mismatch at [%d][%d]: parallel=%.6f, serial=%.6f\n",
+                       i, j, C_parallel[i][j], C_serial[i][j]);
+                return 0;
+            }
+        }
+    }
+    return 1;
+}
+
+int main(int argc, char *argv[])
+{
+    if (argc != 3) {
+        fprintf(stderr, "Usage: %s <N> <num_threads>\n", argv[0]);
+        return 1;
+    }
+
+    N = atoi(argv[1]);
+    nthreads = atoi(argv[2]);
+    if (nthreads > MAX_THREADS) nthreads = MAX_THREADS;
+    if (nthreads > N) nthreads = N;
+
+    rows_per_thread = N / nthreads;
+
+    srand(42);
+
+    A = allocate_matrix(N);
+    B = allocate_matrix(N);
+    C_parallel = allocate_matrix(N);
+    C_serial = allocate_matrix(N);
+
+    init_matrix(A, N);
+    init_matrix(B, N);
+
+    pthread_t threads[MAX_THREADS];
+    int starts[MAX_THREADS];
+
+    double t_start = get_time();
+
+    for (int i = 0; i < nthreads; i++) {
+        starts[i] = i * rows_per_thread;
+        pthread_create(&threads[i], NULL, multiply_thread, &starts[i]);
+    }
+    for (int i = 0; i < nthreads; i++) {
+        pthread_join(threads[i], NULL);
+    }
+
+    double t_end = get_time();
+    double t_parallel = t_end - t_start;
+
+    t_start = get_time();
+    serial_multiply();
+    t_end = get_time();
+    double t_serial = t_end - t_start;
+
+    printf("Matrix size: %d x %d, Threads: %d\n", N, N, nthreads);
+    printf("Parallel time: %.6f s\n", t_parallel);
+    printf("Serial time:   %.6f s\n", t_serial);
+    printf("Speedup: %.4f\n", t_serial / t_parallel);
+    printf("Efficiency: %.4f\n", t_serial / t_parallel / nthreads);
+
+    if (verify()) {
+        printf("Verification: SUCCESS\n");
+    } else {
+        printf("Verification: FAILED\n");
+    }
+
+    free_matrix(A, N);
+    free_matrix(B, N);
+    free_matrix(C_parallel, N);
+    free_matrix(C_serial, N);
+
+    return 0;
+}