jacobian

commit 6f012f346097d5211da2a217b2648e6903cbf305
parent a6f363eaa4ef852062ab2ac8ea969ba6fdad3087
Author: David Freifeld <freifeld.david@gmail.com>
Date:   Fri, 25 Sep 2020 14:38:52 -0700

Attribution + readv() improvements

Diffstat:
M
src/cnn.cpp
 | 
1
+
M
src/experimental/fileread.cpp
 | 
29
+++++++++++++++++++----------

2 files changed, 20 insertions(+), 10 deletions(-)
diff --git a/src/cnn.cpp b/src/cnn.cpp
@@ -19,6 +19,7 @@
 #define checknan(x, loc)
 #endif
 
+// NOTE: Below two functions not mine, from https://compvisionlab.wordpress.com/2014/01/01/c-code-for-reading-mnist-data-set/
 int ReverseInt (int i)
 {
     unsigned char ch1, ch2, ch3, ch4;
diff --git a/src/experimental/fileread.cpp b/src/experimental/fileread.cpp
@@ -128,22 +128,31 @@ float mmap_read()
 
 float vec_read()
 {
+#define CHUNK_SZ 512
+#define BUFFER_SZ 512*1024
+#define NUM_CHUNKS BUFFER_SZ/CHUNK_SZ
     int fd = open("../../data_banknote_authentication.bin", O_RDONLY | O_NONBLOCK);
-    float buf[128];
-    float buf2[128];
-    float buf3[128];
-    float buf4[128];
-    float buf5[128];
-    float buf6[128];
-    float buf7[128];
-    float buf8[128];
-    iovec iovecs[8] {{&buf, 512}, {&buf2, 512}, {&buf3, 512}, {&buf4, 512}, {&buf5, 512}, {&buf6, 512}, {&buf7, 512}, {&buf8, 512}};
-    while(size_t bytes_read = readv(fd, iovecs, 8))
+    char rawbuf[BUFFER_SZ];
+    char* buf = (char*) rawbuf;
+    iovec iovecs[NUM_CHUNKS];
+    //    printf("buf = %p\n", buf);
+    for (int i = 0; i < BUFFER_SZ; i+=CHUNK_SZ) {
+        // printf("iovecs[%d] = {%p, %d}\n", i/512, buf + i, 512);
+        iovecs[i/CHUNK_SZ].iov_base = buf + i;
+        iovecs[i/CHUNK_SZ].iov_len = CHUNK_SZ;
+    }
+    while(size_t bytes_read = readv(fd, iovecs, NUM_CHUNKS))
     {
         if(bytes_read == (size_t)-1) {
+            printf("\n%zu\n", bytes_read);
             printf("bytes_read == (size_t)-1\n");
             exit(1);
         }
+        // for(char *p = buf; p < buf+512;) {
+        //     for (int i=0; i<5; ++i) {
+        //         p += sizeof(float);
+        //     }
+        // }
         if (!bytes_read) break;
     }
 }