Known limitations

These are the known limitations and restrictions in this version of the SDK.

General limitations:

For applications that link with the SDK example shared libraries (such as the libraries whose source is found in /opt/cell/sdk/src/lib) these libraries are not located in a standard library search path. To locate the libraries, set LD_LIBRARY_PATH or specify an rpath when linking the application. For example:
```
LDFLAGS += -R/opt/cellsdk/sdk/usr/lib	    # for 32-bit apps
LDFLAGS += -R/opt/cellsdk/sdk/usr/lib64	  # for 64-bit apps 
```
Or, use the SDKEXRPATH variable that make.footer defines:
```
LDFLAGS += -R${SDKEXRPATH}
```
The cellsdk_select_compiler bash script will allow you to select a compiler, even if it is not installed. The most common case is the xlc option which only functions correctly when the separately available IBM^® XL C/C++ Alpha Edition for Multicore Acceleration for Linux^®, V0.9 package is installed.
When using large pages, there is a risk that your application will terminate when you run it. To remove this problem, ensure that the number of large pages you request does not exceed the number available. To check, type the command `cat /proc/meminfo` and examine the line that says HugePages_Free: near the bottom of the output. Notify your administrator if this number is insufficient.

DaCS for Cell BE and DaCS for Hybrid-x86 limitations:

Performing a dacs_runtime_exit() call immediately after a DaCS for Hybrid-x86 communication operation without an intervening test for communication completion may cause the application to hang. The hang occurs because the exiting application may complete (and terminate communication) before the communication completes, leaving the other application (the one the exiting function was communicating with) in a hung state awaiting the communication. To avoid this problem ensure that your applications allow for communication to complete by testing for completion prior to calling dacs_runtime_exit().
When using the dacs_de_start API, it returns DACS_ERR_SYSTEM instead of INVALID_DACS_ERROR_CODE if the file doesn't exist on the remote machine. To diagnose the problem, set the environment variable DACS_HYBRID_DEBUG=Y and examine the associated log files on the accelerator(s) for the adacsd, typically /var/log/adacsd.log for the failing errno.

GCC Toolchain limitations:

In the SPE, the %l qualifier for printf/scanf is not supported.
When debugging a multi-threaded application, the debugger may get confused if, during a single-step operation on one thread, some other thread reports an event that causes debugging to stop. An example is a new thread is created, a shared library or SPE context is loaded, and some breakpoint is hit. Subsequent single-step operations on the original thread may behave incorrectly. When this occurs, you can restore correct operation of the debugger by not single-stepping and instead continuing the program until it hits another breakpoint.
GDB has trouble correctly tracing an SPE context that is created with events enabled (SPE_EVENTS_ENABLE).
Attempting to build the Linux kernel for Cell BE using the ppu-gcc compiler will fail with an Internal Compiler Error. As a workaround, build the kernel using the system compiler gcc.

Networking limitation:

The eth1 network port on a BladeCenter QS20 may be slower than eth0 when transmitting UDP streams.

Performance Debugging Tool limitations:

PDT tracing in a hybrid system is only supported on AMD Opteron chips that support the RDTSCP (read time-stamp counter and processor ID instruction) introduced in the NPT Family 0Fh processors.

Full-System Simulator limitations:

The libsim library has been removed from the SDK. Sample source code is provided with the simulator that allows users to build their own version of libsim. The source code can be found in /opt/ibm/systemsim-cell/sample/cell/libsim. The first execution of the /opt/cell/cellsdk_sync_simulator script will build the libsim.a library and export it to the /opt/cell/sysroot/usr/spu/lib directory.
The sim_printf.h header file has been removed from the SDK. A sample header file containing a prototype for sim_printf is shipped with the simulator and can be found in the /opt/ibm/systemsim-cell/sample/cell/libsim/spu/libsim.h file. The first execution of the /opt/cell/cellsdk_sync_simulator script will export the libsim.h header file to the /opt/cell/sysroot/usr/spu/include directory.
The level 3 BLAS examples cause a BUS ERROR when they are executed in the Full-System Simulator.