jacobian

commit 0d9d0a6d82aa302b9191fbeabb4e972554e9673f
parent 8b2996b83953d4a1a973a01ed848cd03812b3509
Author: David Freifeld <freifeld.david@gmail.com>
Date:   Sun, 20 Sep 2020 21:21:58 -0700

Fileread continues to be a not straightforward microoptimization that will ultimately end up being a waste of time and make me sad

AVX calls p2 :(

Diffstat:
M
src/experimental/fileread.cpp
 | 
34
++++++++++++++++------------------

1 file changed, 16 insertions(+), 18 deletions(-)
diff --git a/src/experimental/fileread.cpp b/src/experimental/fileread.cpp
@@ -14,6 +14,7 @@
 #include <ctime>
 #include <chrono>
 #include <iostream>
+#include <cmath>
 #include <stdint.h>
 
 // No safety checks whatsoever. Use at your own risk.
@@ -27,7 +28,7 @@
 int main () {
     auto start = std::chrono::high_resolution_clock::now();
     static const auto BUFFER_SIZE = 16*1024;
-    int fd = open("../../data_banknote_authentication.txt", O_RDONLY);
+    int fd = open("../../data_banknote_authentication.txt", O_RDONLY & O_NONBLOCK);
     if(fd == -1) {
         printf("fd == -1\n");
         return 1;
@@ -39,6 +40,7 @@ int main () {
     char buf[BUFFER_SIZE + 1];
     uintmax_t lines = 0;
     float tmp;
+    int bufs = 0;
     while(size_t bytes_read = read(fd, buf, BUFFER_SIZE))
     {
         if(bytes_read == (size_t)-1) {
@@ -46,28 +48,22 @@ int main () {
             return 1;
         }
         if (!bytes_read) break;
-        for(char *p = buf; (p = (char*) memchr(p, '\n', (buf + bytes_read) - p)); ++p) {
-            long bound = (char*) memchr(p+1, '\n', (buf + bytes_read) - p+1) - p;
-            if (bound < 0) break; // Stop.
-            //            printf("%p (%p + %ld) vs %p\n", p+bound, p, bound, buf+BUFFER_SIZE);
+        for(char *p = buf;; ++p) {
+            char* bound = (char*) memchr(p+1, '\n', (buf + bytes_read) - p+1);
+            if (bound - p < 0) break; // Stop.
             tmp = strtod(p, NULL); // Read first float
-            //int delims = 0;
-            //            printf("%f\n", tmp);
-            for (int i = 0; i < bound; i++) { 
-                if (*(p+i) ==  ',') {
-                    tmp = strtod(p+i+1, NULL); // Read float following delimiter
-                    //printf("%f\n", tmp);
-                    // delims++;
-                    // printf("Comma: %f %d\n", tmp, delims);
+            for (; p < bound; ++p) { 
+                if (*p ==  ',') {
+                    tmp = strtod(p, NULL); // Read float following delimiter
                 }
             }
             ++lines;
         }
-        
+        bufs++;
     }
-    printf("Final %f\n", tmp);
+    printf("Final %f, %i bufs\n", tmp, bufs);
     auto end = std::chrono::high_resolution_clock::now();
-    double time = std::chrono::duration_cast<std::chrono::nanoseconds>(end - start).count();
+    double time = std::chrono::duration_cast<std::chrono::nanoseconds>(end - start).count() / pow(10,9);
     
     auto f_start = std::chrono::high_resolution_clock::now();
     int flines = 0;
@@ -86,7 +82,9 @@ int main () {
     }
     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";
     if (ftmp == tmp) std::cout << "Final value read is valid!" << "\n";
-    double ftime = std::chrono::duration_cast<std::chrono::nanoseconds>(f_end - f_start).count();
-    std::cout << ftime << " " << time << " " << ftime/time << "\n";
+    else std::cout << "WARN: INVALID LAST READ VAL " << tmp << " vs. " << ftmp << "\n";
+    double ftime = std::chrono::duration_cast<std::chrono::nanoseconds>(f_end - f_start).count() / pow(10,9);
+    std::cout << ftime << " " << time << " so " << ftime/time << "% speedup\n";
 }