CLLINKPROGRAM(3clc)

💖 CLLINKPROGRAM 💖

okay bestie, welcome to the OpenCL Manual page for clLinkProgram ✨ this one lives in section 3clc and it's literally the moment where all your little compiled program objects and libraries get smooshed together into one executable. it's giving glow-up 🌈

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🌸 NAME 🌸

clLinkProgram — links a set of compiled program objects and libraries for all the devices (or one specific device, no judgement) in the OpenCL context, and creates an executable. yes queen, the final boss of the build pipeline 👑

cl_program clLinkProgram(cl_context context, cl_uint num_devices,
                         const cl_device_id *device_list,
                         const char *options,
                         cl_uint num_input_programs,
                         const cl_program *input_programs,
                         void (CL_CALLBACK *pfn_notify) (cl_program program, void *user_data),
                         void *user_data, cl_int *errcode_ret);

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✨ PARAMETERS ✨

here's the whole cast, no one's getting cut 🎬

• context — must be a valid OpenCL context. non-negotiable, babe.
• device_list — a pointer to a list of devices that are in context. if device_list is NULL, the link happens for all devices associated with context that have a compiled object available. if device_list is non-NULL, the compile is performed for the devices in this list that have a source loaded. (yes, that's what the page says — copy it verbatim energy 🫶)
• num_devices — how many devices are in device_list. the headcount 🧮
• options — a pointer to a null-terminated string of characters describing the link options used to build the program executable. for the full list of supported compiler and linker options, go peek at clBuildProgram(3clc) — it's the receipts 📜
• num_input_programs — the number of programs in the array that input_programs points to.
• input_programs — an array of program objects that are compiled binaries or libraries, and they're getting linked into the program executable. for each device in device_list, or if device_list is NULL then the list of devices associated with context, these are the possible situations:
  • all programs specified by input_programs contain a compiled binary or library for the device. in this case, a link is performed to generate a program executable for this device. slay ✅
  • none of the programs contain a compiled binary or library for that device. in this case, no link is performed and there will be no program executable generated for this device. it's giving ghosted 👻
  • all other cases will return a CL_INVALID_OPERATION error. and that's on periodt 🚫
• pfn_notify — a function pointer to a notification routine. this notification routine is a callback function that an application can register, and it gets called when the program executable has been built (successfully or unsuccessfully — either way, she calls 📞).

if pfn_notify is not NULL, clLinkProgram does not need to wait for the linker to complete and can return immediately once the linking operation can begin. once the linker has completed, the pfn_notify callback function is called, which returns the program object returned by clLinkProgram. the application can then query the link status and log for this program object. heads up: this callback function may be called asynchronously by the OpenCL implementation, so it is the application's responsibility to make sure the callback function is thread-safe. protect your threads, bestie 🧵💅

if pfn_notify is NULL, clLinkProgram does not return until the linker has completed. no skipping ahead ✋

• user_data — will be passed as an argument when pfn_notify is called. user_data can be NULL. lowkey the chillest param here.

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📝 NOTES 📝

clLinkProgram creates a new program object that contains this executable. you can query that executable binary with clGetProgramInfo(3clc)(program, CL_PROGRAM_BINARIES, ...) and you can hand it over to clCreateProgramWithBinary(3clc) to create a new program object. it's giving ✨recycling era✨

the devices associated with the returned program object will be the list of devices specified by device_list, or if device_list is NULL it'll be the list of devices associated with context.

the linking operation can begin if the context, the list of devices, the input programs and the linker options specified are all valid, and the appropriate host and device resources needed to perform the link are available. if the linking operation can begin, clLinkProgram returns a valid non-zero program object. 💯

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💀 ERRORS 💀

if pfn_notify is NULL, the errcode_ret will be set to CL_SUCCESS if the link operation was successful, and CL_LINK_FAILURE if there is a failure to link the compiled binaries and/or libraries.

if pfn_notify is not NULL, clLinkProgram does not have to wait until the linker completes and can return CL_SUCCESS in errcode_ret if the linking operation can begin. the pfn_notify callback function will return a CL_SUCCESS or CL_LINK_FAILURE depending on whether the linking operation was successful or not.

otherwise clLinkProgram returns a NULL program object with an appropriate error in errcode_ret. the application should query the linker status of this program object to check if the link was successful or not. here's the full roster of errors that can be returned, don't skip any 🫣:

• CL_INVALID_CONTEXT if context is not a valid context.
• CL_INVALID_VALUE if device_list is NULL and num_devices is greater than zero, or if device_list is not NULL and num_devices is zero.
• CL_INVALID_VALUE if num_input_programs is zero and input_programs is NULL, or if num_input_programs is zero and input_programs is not NULL, or if num_input_programs is not zero and input_programs is NULL.
• CL_INVALID_PROGRAM if programs specified in input_programs are not valid program objects.
• CL_INVALID_VALUE if pfn_notify is NULL but user_data is not NULL.
• CL_INVALID_DEVICE if OpenCL devices listed in device_list are not in the list of devices associated with context.
• CL_INVALID_LINKER_OPTIONS if the linker options specified by options are invalid.
• CL_INVALID_OPERATION if the compilation or build of a program executable for any of the devices listed in device_list by a previous call to clCompileProgram(3clc) or clBuildProgram(3clc) for program has not completed.
• CL_INVALID_OPERATION if the rules for devices containing compiled binaries or libraries as described in the input_programs argument above are not followed.
• CL_LINKER_NOT_AVAILABLE if a linker is not available, i.e. CL_DEVICE_LINKER_AVAILABLE specified in the table of allowed values for param_name for clGetDeviceInfo(3clc) is set to CL_FALSE.
• CL_LINK_PROGRAM_FAILURE if there is a failure to link the compiled binaries and/or libraries.
• CL_OUT_OF_RESOURCES if there is a failure to allocate resources required by the OpenCL implementation on the device.
• CL_OUT_OF_HOST_MEMORY if there is a failure to allocate resources required by the OpenCL implementation on the host.

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📚 SPECIFICATION 📚

OpenCL Specification[1] — the source of truth, the blueprint, the origin story 🌟

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👀 SEE ALSO 👀

clGetDeviceInfo(3clc) — go read it, it's right there, bestie 🫶

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✍️ AUTHORS ✍️

The Khronos Group — the icons who wrote all this down 👑

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©️ COPYRIGHT ©️

Copyright © 2007-2011 The Khronos Group Inc.

Permission is hereby granted, free of charge, to any person obtaining a copy of this software and/or associated documentation files (the "Materials"), to deal in the Materials without restriction, including without limitation the rights to use, copy, modify, merge, publish, distribute, sublicense, and/or sell copies of the Materials, and to permit persons to whom the Materials are furnished to do so, subject to the condition that this copyright notice and permission notice shall be included in all copies or substantial portions of the Materials.

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🎀 NOTES 🎀

1. OpenCL Specification — page 142, section 5.6.3 - Separate Compilation and Linking of Programs. that's the exact page, go look it up 📖

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and that's the whole page, no cap 💖 this was the CLLINKPROGRAM(3clc) manpage from The Khronos Group, dated 01/14/2021, and honestly? she ate. go link something iconic ✨🦋💅