More opencl info

Author: cirosantilli

c/common.h

@@ -19,8 +19,8 @@
 #include <time.h> /* time() */
 #include <wchar.h>
 #if __STDC_VERSION__ >= 199901L
-  /* Not yet implemented in GCC 4.8. */
-  /*#include <thread.h>*/
+  /* Not yet implemented in GCC 5.2. */
+/*#  include <threads.h>*/
 # ifndef __STDC_NO_COMPLEX__
 #  include <complex.h>
 # endif

cpp/interactive/thread_count.cpp

@@ -0,0 +1,21 @@
+/*
+Dummy operation that uses a lot of CPU, but very little memory.
+
+Used as a control for the parallel version, which should me scalably faster.
+*/
+
+#include "common.hpp"
+
+void sleeper() {
+    std::this_thread::sleep_for(std::chrono::seconds(1000000));
+}
+
+int main() {
+    unsigned int nThreads = std::thread::hardware_concurrency();
+    std::thread *threads = new std::thread[nThreads];
+    unsigned int i;
+    for (i = 0; i < nThreads; ++i)
+        threads[i] = std::thread(sleeper);
+    for (i = 0; i < nThreads; ++i)
+        threads[i].join();
+}

cpp/reference.cpp

@@ -3,7 +3,7 @@
 
 # &
 
-    Basically aliases, similar to `int* const` poinsters or java objects.
+    Basically aliases, similar to `int* const` pointers or Java objects.
 
     Useful only for function arguments or / return values. In that case the pros are:
 
@@ -15,13 +15,20 @@
     The cons are:
 
     - callers don't know without looking at the signature if they are passing references or copies,
-        and wether they should expect that it is possible that the functio modifies their object.
+        and whether they should expect that it is possible that the function modifies their object.
 
-    Just like for pointers, you have to watch scope. If the original object dies,
-    you get a dangling reference
-
-    - http://stackoverflow.com/questions/752658/is-the-practice-of-returning-a-c-reference-variable-evil
     - http://stackoverflow.com/questions/7058339/c-when-to-use-references-vs-pointers
+
+    # Return reference from function
+
+        Just like for pointers, you have to watch scope. If the original object dies,
+        you get a dangling reference
+
+        - http://stackoverflow.com/questions/752658/is-the-practice-of-returning-a-c-reference-variable-evil
+
+        There is also some rule about const local references:
+
+        - http://stackoverflow.com/questions/2784262/does-a-const-reference-prolong-the-life-of-a-temporary
 */
 
 #include "common.hpp"

cpp/vector.cpp

@@ -125,7 +125,6 @@ int main() {
 
             // Increase size
             {
-
                 // Using default constructor objects.
                 {
                     std::vector<int> v{1};

opencl/bibliography.md

@@ -4,3 +4,9 @@
 - <http://developer.amd.com/tools-and-sdks/opencl-zone/opencl-resources/>
 - <http://www.fixstars.com/en/opencl/book/OpenCLProgrammingBook>
 - The specifications of your hardware, e.g. <http://www.nvidia.com/object/nvs_techspecs.html>
+
+Tutorials with sample code:
+
+- <https://github.com/sschaetz/nvidia-opencl-examples>
+- <https://github.com/enjalot/adventures_in_opencl> Did not work out of the box for me.
+- <https://github.com/bgaster/opencl-book-samples> The book is commercial.

opencl/getting-started.md

@@ -2,18 +2,4 @@
 
 ## NVIDIA
 
-On Ubuntu 15.10 with an NVIDIA NVS 5400M, Lenovo T430:
-
-    sudo apt-get install nvidia-352 nvidia-352-dev nvidia-prime
-    sudo ln -s /usr/include/nvidia-352/GL /usr/local/include
-    sudo ln -s /usr/lib/x86_64-linux-gnu/libOpenCL.so.1 /usr/local/lib/libOpenCL.so
-
-Then compile with:
-
-	gcc -o main main.c -lOpenCL
-
-Notes:
-
-- find your GPU model: <http://askubuntu.com/questions/72766/how-do-i-find-out-the-model-of-my-graphics-card>
-- test that the driver is working: <http://askubuntu.com/questions/68028/how-do-i-check-if-ubuntu-is-using-my-nvidia-graphics-card>
-- do not install the `nvidia-current` package. It is old. Either `apt-cache search nvidia` and get the latest one, or use `software-properties-gtk` "Additional Drivers" tab.
+On Ubuntu 15.10 with an NVIDIA NVS 5400M, Lenovo T430: <http://askubuntu.com/questions/541114/how-to-make-opencl-work-on-14-10-nvidia-331-89-drivers/693043#693043>

opencl/introduction.md

@@ -26,8 +26,20 @@ Looks like the major open source implementation.
 
 ### pocl
 
+Portable OpenCL implementation.
+
 <https://github.com/pocl/pocl>
 
 <http://portablecl.org/>
 
 MIT and LLVM based.
+
+## Tools
+
+- <http://repo.or.cz/w/ppcg.git> C99 to OpenCL.
+
+## Alternatives
+
+- OpenMP: <http://stackoverflow.com/questions/7263193/opencl-performance-vs-openmp>
+- <https://en.wikipedia.org/wiki/Unified_Parallel_C>
+- <https://en.wikipedia.org/wiki/Cilk>

opengl/TODO.md

@@ -1,3 +1,4 @@
 # TODO
 
 -   Are the OpenGL types fixed size? How to properly printf them?
+-   How to select the rendering device? <http://stackoverflow.com/questions/6036292/select-a-graphic-device-in-windows-opengl> `prime-select`?

posix/interactive/pthread_count.c

@@ -0,0 +1,29 @@
+/*
+To see if
+
+    ./pthread_count.out &
+    cat /proc/$!/status | grep -i thread
+    kill $!
+
+shows the right thread count.
+*/
+
+#include "common.h"
+
+void* main_thread(void *arg) {
+    sleep(1000000);
+    return NULL;
+}
+
+int main() {
+    int i;
+    enum NUM_THREADS {NUM_THREADS = 4};
+    pthread_t threads[NUM_THREADS];
+    for (i = 0; i < NUM_THREADS; ++i) {
+        pthread_create(&threads[i], NULL, main_thread, NULL);
+        printf("tid: %ju\n", (uintmax_t)threads[i]);
+    }
+    for (i = 0; i < NUM_THREADS; ++i) {
+        pthread_join(threads[i], NULL);
+    }
+}