Documentation updates
Change-Id: Ia624d86915c4c96da0ac0242f767135f30ff73c6
This commit is contained in:
Maneesh Gupta
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# FAQ
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- [What APIs and features does HIP support ?](#Q1)
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- [What is not supported?](#Q2)
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- [Run-time features](#run-time-features)
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- [Kernel language features](#kernel-language-features)
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- [Is HIP a drop-in replacement for CUDA?](#Q3)
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- [What version of CUDA is supported?](#Q4)
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- [What libraries does HIP support?](#Q5)
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<!-- toc -->
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- [What APIs and features does HIP support?](#what-apis-and-features-does-hip-support)
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- [What is not supported?](#what-is-not-supported)
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* [Run-time features](#run-time-features)
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* [Kernel language features](#kernel-language-features)
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- [Is HIP a drop-in replacement for CUDA?](#is-hip-a-drop-in-replacement-for-cuda)
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- [What version of CUDA is supported?](#what-version-of-cuda-is-supported)
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- [What libraries does HIP support?](#what-libraries-does-hip-support)
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- [How does HIP compare with OpenCL?](#how-does-hip-compare-with-opencl)
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- [What hardware does HIP support?](#what-hardware-does-hip-support)
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- [Does Hipify automatically convert all source code?](#does-hipify-automatically-convert-all-source-code)
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@@ -18,10 +20,13 @@
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- [Can a HIP binary run on both AMD and Nvidia platforms?](#can-a-hip-binary-run-on-both-amd-and-nvidia-platforms)
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- [What's the difference between HIP and hc?](#whats-the-difference-between-hip-and-hc)
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- [HIP detected my platform (hcc vs nvcc) incorrectly - what should I do?](#hip-detected-my-platform-hcc-vs-nvcc-incorrectly---what-should-i-do)
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- [How do I trace HIP application flow?](#how-do-i-trace-hip-application-flow)
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* [Using CodeXL markers for HIP Functions](#using-codexl-markers-for-hip-functions)
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* [Using HIP_TRACE_API](#using-hip_trace_api)
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<!-- tocstop -->
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### What APIs and features does HIP support?<a name="Q1"></a>
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### What APIs and features does HIP support?
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HIP provides the following:
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- Devices (hipSetDevice(), hipGetDeviceProperties(), etc.)
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- Memory management (hipMalloc(), hipMemcpy(), hipFree(), etc.)
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@@ -34,7 +39,7 @@ HIP provides the following:
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The HIP API documentation describes each API and its limitations, if any, compared with the equivalent CUDA API.
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### What is not supported?<a name="Q2"></a>
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### What is not supported?
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#### Run-time features
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- Textures
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- MemcpyToSymbol functions
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@@ -51,12 +56,12 @@ The HIP API documentation describes each API and its limitations, if any, compar
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- PTX assembly (CUDA 4.0)
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- Several kernel features are under development. See the [HIP Kernel Language](hip_kernel_language.md) for more information.
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### Is HIP a drop-in replacement for CUDA?<a name="Q3"></a>
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### Is HIP a drop-in replacement for CUDA?
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No. HIP provides porting tools which do most of the work do convert CUDA code into portable C++ code that uses the HIP APIs.
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Most developers will port their code from CUDA to HIP and then maintain the HIP version.
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HIP code provides the same performance as coding in native CUDA, plus the benefit that the code can also run on AMD platforms.
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### What version of CUDA is supported?<a name="Q4"></a>
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### What version of CUDA is supported?
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HIP APIs and features do not map to a specific CUDA version. HIP provides a strong subset of functionality provided in CUDA, and the hipify tools can
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scan code to identify any unsupported CUDA functions - this is very useful for identifying the specific features required by a given application.
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@@ -81,7 +86,7 @@ However, we can provide a rough summary of the features included in each CUDA SD
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- CUDA 8.0
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- No new language features.
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### What libraries does HIP support? <a name="Q5"></a>
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### What libraries does HIP support?
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HIP includes growing support for the 4 key math libraries using hcBlas, hcFft, hcrng, and hcsparse).
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These offer pointer-based memory interfaces (as opposed to opaque buffers) and can be easily interfaces with other HCC code. Developers should use conditional compliation if portability to nvcc systems is desired - using calls to cu* routines on one path and hc* routines on the other.
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@@ -147,7 +152,6 @@ A C++ dialect, hc is supported by the AMD HCC compiler. It provides C++ run time
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### HIP detected my platform (hcc vs nvcc) incorrectly - what should I do?
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HIP will set the platform to HCC if it sees that the AMD graphics driver is installed and has detected an AMD GPU.
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Sometimes this isn't what you want - you can force HIP to recognize the platform by setting HIP_PLATFORM to hcc (or nvcc)
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```
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@@ -157,3 +161,40 @@ export HIP_PLATFORM=hcc
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One symptom of this problem is the message "error: 'unknown error'(11) at square.hipref.cpp:56". This can occur if you have a CUDA installation on an AMD platform, and HIP incorrectly detects the platform as nvcc. HIP may be able to compile the application using the nvcc tool-chain, but will generate this error at runtime since the platform does not have a CUDA device. The fix is to set HIP_PLATFORM=hcc and rebuild the issue.
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If you see issues related to incorrect platform detection, please file an issue with the GitHub issue tracker so we can improve HIP's platform detection logic.
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### How do I trace HIP application flow?
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#### Using CodeXL markers for HIP Functions
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HIP can generate markers at function being/end which are displayed on the CodeXL timeline view.
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To do this, you need to install ROCm-Profiler and enable HIP to generate the markers:
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1. Install ROCm-Profiler
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Installing HIP from the [rocm](http://gpuopen.com/getting-started-with-boltzmann-components-platforms-installation/) pre-built packages, installs the ROCm-Profiler as well.
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Alternatively, you can build ROCm-Profiler using the instructions [here](https://github.com/RadeonOpenCompute/ROCm-Profiler#building-the-rocm-profiler).
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2. Build HIP with ATP markers enabled
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HIP pre-built packages are enabled with ATP marker support by default.
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To enable ATP marker support when building HIP from source, use the option ```-DCOMPILE_HIP_ATP_MARKER=1``` during the cmake configure step.
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3. Set HIP_ATP_MARKER
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```shell
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export HIP_ATP_MARKER=1
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```
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4. Recompile the target application
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5. Run with profiler enabled to generate ATP file.
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```shell
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# Use profile to generate timeline view:
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/opt/rocm/bin/rocm-profiler -o <outputATPFileName> -A <applicationName> <applicationArguments>
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```
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#### Using HIP_TRACE_API
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You can also print the HIP function strings to stderr using HIP_TRACE_API environment variable. This can also be combined with the more detailed debug information provided
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by the HIP_DB switch. For example:
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```shell
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# Trace to stderr showing being/end of each function (with arguments) + intermediate debug trace during the execution of each function.
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HIP_TRACE_API=1 HIP_DB=0x2 ./myHipApp
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```
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Note this trace mode uses colors. "less -r" can handle raw control characters and will display the debug output in proper colors.
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