CLENQUEUEWRITEBUFFER(3clc)

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version 1.0~svn33624 · 3 versions
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💖 CLENQUEUEWRITEBUFFER 💖

okay bestie, welcome to the clEnqueueWriteBuffer page from the OpenCL Manual (that's 3clc to the section-name girlies) 💅 this is the one that yeets data from your host memory into a buffer object, and it is genuinely iconic. let's go 🫶

✨ NAME ✨

clEnqueueWriteBuffer — enqueue commands to write to a buffer object from host memory. no cap, that's literally the whole job.

cl_int clEnqueueWriteBuffer(cl_command_queue command_queue,
                            cl_mem buffer, cl_bool blocking_write,
                            size_t offset, size_t size, const void *ptr,
                            cl_uint num_events_in_wait_list,
                            const cl_event *event_wait_list,
                            cl_event *event);

🌸 PARAMETERS 🌸

  • command_queue — the command-queue where this write command is gonna get queued up, bestie. heads up: command_queue and buffer must be created with the same OpenCL context or it's a whole thing.
  • buffer — a valid buffer object, pls. that's it. that's the vibe.
  • blocking_write — tells you if the write is blocking or nonblocking, and this one actually matters so listen up 🔥
    • if blocking_write is CL_TRUE, the OpenCL implementation copies the data that ptr points to and enqueues the write operation into the command-queue. so once clEnqueueWriteBuffer returns, the memory that ptr points at is yours again and you can reuse it. slay.
    • if blocking_write is CL_FALSE, the implementation will use ptr to do a nonblocking write. since it's non-blocking it can return immediately. so the memory that ptr points at cannot be reused by the application after the call returns. 😭 the event argument hands you back an event object you can use to query the execution status of the write command. once the write command has completed, then the memory pointed to by ptr can be reused by the application. patience, queen.
  • offset — the offset in bytes in the buffer object to write to.
  • size — the size in bytes of the data being written.
  • ptr — the pointer to the buffer in host memory where data is to be written from.
  • event_wait_list, num_events_in_wait_list — these two specify events that need to complete before this particular command can even be executed. if event_wait_list is NULL, then this particular command doesn't wait on any event to complete. and if event_wait_list is NULL, then num_events_in_wait_list must be 0. if event_wait_list is not NULL, the list of events pointed to by event_wait_list must be valid and num_events_in_wait_list must be greater than 0. the events in event_wait_list act as synchronization points ✨ the context associated with the events in event_wait_list and command_queue must be the same. the memory associated with event_wait_list can be reused or freed after the function returns. so efficient.
  • event — returns an event object that identifies this particular write command, and you can use it to query or queue a wait for this particular command to complete. event can be NULL, in which case it will not be possible for the application to query the status of this command or queue a wait for this command to complete. so like… your call, but just know what you're giving up 🙈

🦋 NOTES 🦋

calling clEnqueueWriteBuffer to update the latest bits in a region of the buffer object, with the ptr argument value set to host_ptr + offset — where host_ptr is a pointer to the memory region specified when the buffer object being written was created with CL_MEM_USE_HOST_PTR — must meet the following requirements in order to avoid undefined behavior. and undefined behavior is not the moment, bestie. do not skip these.

  • the host memory region given by (host_ptr + offset, cb) contains the latest bits when the enqueued write command begins execution.
  • the buffer object or memory objects created from this buffer object are not mapped.
  • the buffer object or memory objects created from this buffer object are not used by any command-queue until the read command has finished execution.

💀 ERRORS 💀

clEnqueueWriteBuffer returns CL_SUCCESS if the function is executed successfully. otherwise, it returns one of the following errors, and there are a lot of them, so buckle up:

  • CL_INVALID_COMMAND_QUEUE if command_queue is not a valid command-queue.
  • CL_INVALID_CONTEXT if the context associated with command_queue and buffer are not the same, or if the context associated with command_queue and events in event_wait_list are not the same.
  • CL_INVALID_MEM_OBJECT if buffer is not a valid buffer object.
  • CL_INVALID_VALUE if the region being written specified by (offset, size) is out of bounds, or if ptr is a NULL value, or if size is 0.
  • CL_INVALID_EVENT_WAIT_LIST if event_wait_list is NULL and num_events_in_wait_list greater than 0, or event_wait_list is not NULL and num_events_in_wait_list is 0, or if event objects in event_wait_list are not valid events.
  • CL_MISALIGNED_SUB_BUFFER_OFFSET if buffer is a sub-buffer object and the offset specified when the sub-buffer object is created is not aligned to CL_DEVICE_MEM_BASE_ADDR_ALIGN value for the device associated with queue.
  • CL_EXEC_STATUS_ERROR_FOR_EVENTS_IN_WAIT_LIST if the read and write operations are blocking and the execution status of any of the events in event_wait_list is a negative integer value.
  • CL_MEM_OBJECT_ALLOCATION_FAILURE if there is a failure to allocate memory for data store associated with buffer.
  • CL_INVALID_OPERATION if clEnqueueWriteBuffer(3clc) is called on buffer which has been created with CL_MEM_HOST_READ_ONLY or CL_MEM_HOST_NO_ACCESS.
  • 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.

🌈 SPECIFICATION 🌈

OpenCL Specification[1] — that's the source of truth, go read it, it's giving authority ✨

🎀 SEE ALSO 🎀

👑 AUTHORS 👑

The Khronos Group — absolute legends, no notes.

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.

📖 NOTES 📖

  1. OpenCL Specification page 72, section 5.2.2 - Reading, Writing, Copying Buffer Objects

and that's the whole page, bestie 🥰 this was brought to you by The Khronos Group, dated 01/14/2021, and you can find it filed under CLENQUEUEWRITEBUFFER(3clc) if you ever need to come back to it. mwah 💅🫶

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