From 794bcf9d1c6d3c83a07787fd54e0495826cd293f Mon Sep 17 00:00:00 2001
From: Olivia Fernandez <olivia.fernandez@jampp.com>
Date: Sun, 30 Jan 2022 18:38:02 -0300
Subject: [PATCH] use fork to parallel covariance

---
 fftma_module/gen/lib_src/chunk_array.c | 18 ++++++++++--
 fftma_module/gen/lib_src/covariance.c  | 39 ++++++++++++++++++++++++--
 2 files changed, 51 insertions(+), 6 deletions(-)

diff --git a/fftma_module/gen/lib_src/chunk_array.c b/fftma_module/gen/lib_src/chunk_array.c
index 75eb201..6a5a196 100644
--- a/fftma_module/gen/lib_src/chunk_array.c
+++ b/fftma_module/gen/lib_src/chunk_array.c
@@ -2,8 +2,11 @@
 #include "stdbool.h"
 #include "stdlib.h"
 #include <sys/mman.h>
+#include <sys/stat.h>
+#include <fcntl.h>
+#include <unistd.h>
 
-#define MAX_CHUNK_SIZE 2048*2048
+#define MAX_CHUNK_SIZE 268435456
 
 int min(int value1, int value2) {
     if (value1 < value2) return value1;
@@ -94,12 +97,22 @@ chunk_array_t* chunk_array_create(char* filename, size_t total_size) {
         return NULL;
     }
 
-    chunk_array->mmap_array = mmap ( NULL, total_size*sizeof(double), PROT_READ | PROT_WRITE, MAP_PRIVATE | MAP_ANONYMOUS, 0, 0 );
+    int fd = open(filename, O_RDWR | O_CREAT, 0644);
+    if(fd < 0){
+        free(chunk_array);
+        return NULL;
+    }
+
+    chunk_array->mmap_array = mmap ( NULL, total_size * sizeof(double), PROT_READ | PROT_WRITE, MAP_SHARED, fd, 0 );
 
     if (chunk_array->mmap_array == NULL) {
+        free(chunk_array);
         return NULL;
     }
 
+    ftruncate(fd, total_size * sizeof(double));
+    close(fd);
+
     chunk_array->chunk_size = min(MAX_CHUNK_SIZE, total_size);
 
     chunk_array->buffer1 = buffer_create(chunk_array->chunk_size);
@@ -113,7 +126,6 @@ chunk_array_t* chunk_array_create(char* filename, size_t total_size) {
     chunk_array->buffer2 = buffer_create(chunk_array->chunk_size);
 
     if (chunk_array->buffer2 == NULL) {
-        //fclose(chunk_array->fp);
         buffer_free(chunk_array->buffer1);
         free(chunk_array);
         return NULL;
diff --git a/fftma_module/gen/lib_src/covariance.c b/fftma_module/gen/lib_src/covariance.c
index a96a652..4ff4030 100644
--- a/fftma_module/gen/lib_src/covariance.c
+++ b/fftma_module/gen/lib_src/covariance.c
@@ -4,14 +4,14 @@
 
 /*builds the sampled covariance function*/
 /*dimensions are even*/
-void covariance(chunk_array_t* covar, struct vario_mod variogram, struct grid_mod mesh, int n[3]) {
-    int i, j, k, maille, n2[3], symmetric;
+void process(chunk_array_t* covar, struct vario_mod variogram, struct grid_mod mesh, int n[3], int n2[3], int init, int end) {
+    int i, j, k, maille, symmetric;
     double di, dj, dk;
 
     for (i = 0; i < 3; i++)
         n2[i] = n[i] / 2;
 
-    for (i = 0; i <= n2[0]; i++) {
+    for (i = init; i <= end; i++) {
         for (j = 0; j <= n2[1]; j++) {
             for (k = 0; k <= n2[2]; k++) {
 
@@ -84,3 +84,36 @@ void covariance(chunk_array_t* covar, struct vario_mod variogram, struct grid_mo
         }
     }
 }
+
+
+/*builds the sampled covariance function*/
+/*dimensions are even*/
+void covariance(chunk_array_t* covar, struct vario_mod variogram, struct grid_mod mesh, int n[3]) {
+    int n2[3];
+    int i;
+
+    for (i = 0; i < 3; i++) {
+        n2[i] = n[i] / 2;
+    }
+
+    int init, end;
+
+    // child process because return value zero
+    if (fork() == 0) {
+        printf("Covar child\n");
+        init = 0;
+        end = n2[0]/2;
+        process(covar, variogram, mesh, n, n2, init, end);
+        exit(0);
+    }
+    // parent process because return value non-zero.
+    else {
+        printf("Covar parent\n");
+        init = n2[0]/2 + 1;
+        end = n2[0];
+        process(covar, variogram, mesh, n, n2, init, end);
+        wait(NULL);
+    }
+
+    printf("finish covariance\n");
+}