jacobian

commit ffb5d096f474e9931033b74dd12a9eabb9e687bb
parent f8f9b481a76ff638cf082a41db6e02465ce7c5ef
Author: David Freifeld <freifeld.david@gmail.com>
Date:   Wed, 23 Sep 2020 09:58:14 -0700

Testing use of fcntl with RDADVISE

Diffstat:
M
src/experimental/fileread.cpp
 | 
53
++++++++++++++++++++++++++++++++++++++++++-----------

1 file changed, 42 insertions(+), 11 deletions(-)
diff --git a/src/experimental/fileread.cpp b/src/experimental/fileread.cpp
@@ -117,13 +117,44 @@ float newer()
             exit(1);
         }
         if (!bytes_read) break;
-        for(char *p = buf; p < buf+BUFFER_SIZE;) {
-            for (int i=0; i<5; ++i) {
-                tmp = *((float*)p);
-                p += sizeof(float);
-            }
-            ++lines;
+        // for(char *p = buf; p < buf+BUFFER_SIZE;) {
+        //     for (int i=0; i<5; ++i) {
+        //         tmp = *((float*)p);
+        //         p += sizeof(float);
+        //     }
+        //     ++lines;
+        // }
+    }
+    return tmp;
+}
+
+float newest()
+{
+    static const auto BUFFER_SIZE = 600*1024;
+    int fd = open("../../data_banknote_authentication.bin", O_RDONLY | O_NONBLOCK);
+    fcntl(fd, F_RDADVISE);
+    uintmax_t maxlines = 1003222;
+    if(fd == -1) {
+        printf("Cannot open file.");
+        exit(1);
+    }
+    char buf[BUFFER_SIZE];
+    uintmax_t lines = 0;
+    float tmp;
+    while(size_t bytes_read = read(fd, buf, BUFFER_SIZE))
+    {
+        if(bytes_read == (size_t)-1) {
+            printf("bytes_read == (size_t)-1\n");
+            exit(1);
         }
+        if (!bytes_read) break;
+        // for(char *p = buf; p < buf+BUFFER_SIZE;) {
+        //     for (int i=0; i<5; ++i) {
+        //         tmp = *((float*)p);
+        //         p += sizeof(float);
+        //     }
+        //     ++lines;
+        // }
     }
     return tmp;
 }
@@ -132,19 +163,19 @@ int main () {
     int epochs = 1;
     float tmp;
     auto start = std::chrono::high_resolution_clock::now();
-    prep();
+    //prep();
     auto prep_end = std::chrono::high_resolution_clock::now();
     for (int i = 0; i < epochs; i++) {
-        tmp = newer();
+        tmp = newest();
     }
     auto end = std::chrono::high_resolution_clock::now();
     double time = std::chrono::duration_cast<std::chrono::nanoseconds>(end - prep_end + prep_end-start).count() / pow(10,9);
     double runtime = std::chrono::duration_cast<std::chrono::nanoseconds>(end - prep_end).count() / pow(10,9);
     float ftmp;
     auto f_start = std::chrono::high_resolution_clock::now();
-    // for (int i = 0; i < epochs; i++) {
-    //     ftmp = current();
-    // }
+    for (int i = 0; i < epochs; i++) {
+        ftmp = newer();
+    }
     auto f_end = std::chrono::high_resolution_clock::now();
     // if (flines == lines) std::cout << "Linecount is valid!" << "\n";
     // else std::cout << "WARN: INVALID LINECOUNT " << lines << " vs. " << flines << "\n";