# Platform¶

class OpenMM::Platform

A Platform defines an implementation of all the kernels needed to perform some calculation. More precisely, a Platform object acts as a registry for a set of KernelFactory objects which together implement the kernels. The Platform class, in turn, provides a static registry of all available Platform objects.

To get a Platform object, call

Platform& platform = Platform::findPlatform(kernelNames);


passing in the names of all kernels that will be required for the calculation you plan to perform. It will return the fastest available Platform which provides implementations of all the specified kernels. You can then call createKernel() to construct particular kernels as needed.

Methods

 ~Platform getName Get the name of this platform. getSpeed Get an estimate of how fast this Platform class is. supportsDoublePrecision Get whether this Platform supports double precision arithmetic. getPropertyNames Get the names of all Platform-specific properties this Platform supports. getPropertyValue Get the value of a Platform-specific property for a Context. setPropertyValue Set the value of a Platform-specific property for a Context. getPropertyDefaultValue Get the default value of a Platform-specific property. setPropertyDefaultValue Set the default value of a Platform-specific property. contextCreated This is called whenever a new Context is created. linkedContextCreated This is called whenever a new Context is created using ContextImpl::createLinkedContext(). contextDestroyed This is called whenever a Context is deleted. registerKernelFactory Register a KernelFactory which should be used to create Kernels with a particular name. supportsKernels Determine whether this Platforms provides implementations of a set of kernels. createKernel Create a Kernel object.
~Platform()
const std::string &getName() const = 0

Get the name of this platform. This should be a unique identifier which can be used to recognized it.

double getSpeed() const = 0

Get an estimate of how fast this Platform class is. This need not be precise. It only is expected to return an order or magnitude estimate of the relative performance of different Platform classes. An unoptimized reference implementation should return 1.0, and all other Platforms should return a larger value that is an estimate of how many times faster they are than the reference implementation.

bool supportsDoublePrecision() const = 0

Get whether this Platform supports double precision arithmetic. If this returns false, the platform is permitted to represent double precision values internally as single precision.

Deprecated

This method is not well defined, and is too simplistic to describe the actual behavior of some Platforms, such as ones that offer multiple precision modes. It will be removed in a future release.

const std::vector<std::string> &getPropertyNames() const

Get the names of all Platform-specific properties this Platform supports.

const std::string &getPropertyValue(const Context &context, const std::string &property) const

Get the value of a Platform-specific property for a Context.

• context – the Context for which to get the property
• property – the name of the property to get
Returns: the value of the property
void setPropertyValue(Context &context, const std::string &property, const std::string &value) const

Set the value of a Platform-specific property for a Context.

• context – the Context for which to set the property
• property – the name of the property to set
• value – the value to set for the property
const std::string &getPropertyDefaultValue(const std::string &property) const

Get the default value of a Platform-specific property. This is the value that will be used for newly created Contexts.

• property – the name of the property to get
Returns: the default value of the property
void setPropertyDefaultValue(const std::string &property, const std::string &value)

Set the default value of a Platform-specific property. This is the value that will be used for newly created Contexts.

• property – the name of the property to set
• value – the value to set for the property
void contextCreated(ContextImpl &context, const std::map<std::string, std::string> &properties) const

This is called whenever a new Context is created. It gives the Platform a chance to initialize the context and store platform-specific data in it.

• context – the newly created context
• properties – a set of values for platform-specific properties. Keys are the property names.
void linkedContextCreated(ContextImpl &context, ContextImpl &originalContext) const

This is called whenever a new Context is created using ContextImpl::createLinkedContext(). It gives the Platform a chance to initialize the context and store platform-specific data in it.

• context – the newly created context
• originalContext – the original context it is linked to
void contextDestroyed(ContextImpl &context) const

This is called whenever a Context is deleted. It gives the Platform a chance to clean up any platform-specific data that was stored in it.

void registerKernelFactory(const std::string &name, KernelFactory *factory)

Register a KernelFactory which should be used to create Kernels with a particular name. The Platform takes over ownership of the factory, and will delete it when the Platform itself is deleted.

• name – the kernel name for which the factory should be used
• factory – the factory to use for creating Kernels with the specified name
bool supportsKernels(const std::vector<std::string> &kernelNames) const

Determine whether this Platforms provides implementations of a set of kernels.

• kernelNames – the names of the kernels of interests
Returns: true if this Platform provides implementations of all the kernels in the list, false if there are any which it does not support
Kernel createKernel(const std::string &name, ContextImpl &context) const

Create a Kernel object. If you call this method multiple times for different contexts with the same name, the returned Kernels are independent and do not interact with each other. This means that it is possible to have multiple simulations in progress at one time without them interfering.

If no KernelFactory has been registered for the specified name, this will throw an exception.

• name – the name of the Kernel to get
• context – the context for which to create a Kernel
Returns: a newly created Kernel object
void registerPlatform(Platform *platform)

Register a new Platform.

int getNumPlatforms()

Get the number of Platforms that have been registered.

Platform &getPlatform(int index)

Get a registered Platform by index.

std::vector<std::string> getPluginLoadFailures()

Get any failures caused during the last call to loadPluginsFromDirectory

Platform &getPlatformByName(const std::string &name)

Get the registered Platform with a particular name. If no Platform with that name has been registered, this throws an exception.

Platform &findPlatform(const std::vector<std::string> &kernelNames)

Find a Platform which can be used to perform a calculation.

• kernelNames – the names of all kernels which will be needed for the calculation
Returns: the fastest registered Platform which supports all of the requested kernels. If no Platform exists which supports all of them, this will throw an exception.
void loadPluginLibrary(const std::string &file)

Load a dynamic library (DLL) which contains an OpenMM plugin. Typically, each Platform is distributed as a separate dynamic library. This method can then be called at runtime to load each available library. Each library should contain an initializer function to register any Platforms and KernelFactories that it contains.

If the file does not exist or cannot be loaded, an exception is thrown.

• file – the path to the dynamic library file. This is interpreted using the operating system’s rules for loading libraries. Typically it may be either an absolute path or relative to a set of standard locations.
std::vector<std::string> loadPluginsFromDirectory(const std::string &directory)

Load multiple dynamic libraries (DLLs) which contain OpenMM plugins from a single directory. This method loops over every file contained in the specified directory and calls loadPluginLibrary() for each one. If an error occurs while trying to load a particular file, that file is simply ignored. You can retrieve a list of all such errors by calling getPluginLoadFailures().

• directory – the path to the directory containing libraries to load
Returns: the names of all files which were successfully loaded as libraries
const std::string &getDefaultPluginsDirectory()

Get the default directory from which to load plugins. If the environment variable OPENMM_PLUGIN_DIR is set, this returns its value. Otherwise, it returns a platform specific default location.

Returns: the path to the default plugin directory
const std::string &getOpenMMVersion()

Get a string containing the version number of the OpenMM library.