Page 88 - DCAP408_WEB_PROGRAMMING

Windows Programming

Notes Local memory is however managed such that consecutive 32-bit words are used by consecutive
thread IDs. Accesses are as a result fully coalesced as long as all threads in a warp access the
similar relative address (e.g. similar index in an array variable, similar member in a structure
variable). On devices of compute capability 2.0, local memory accesses are at all times cached in
L1 and L2 in the similar manner as global memory accesses
Self Assessment

Fill in the blanks:
1. .................... memory exists in device memory and device memory is used through 32,
64–, or 128-byte memory transactions.
2. For structures, the size and alignment necessities can be enforced by the compiler using
the alignment .....................

3. .................... memory accesses only happen for some automatic variables.
5.2 Local Memory Blocks

Under Win16, there are two major groups of memory API functions: Global and Local. Global-
type API calls deal with memory assigned in other segments therefore they’re “far” memory
functions. Local-type API calls deal with the local heap of the process so they’re “near” memory
functions. Under Win32, these two types are indistinguishable. Whether you call GlobalAlloc or
LocalAlloc, you get the similar result.
Steps in assigning and using memory are as below:
1. Assign a block of memory by calling LocalAlloc. This function returns a handle to the
requested memory block.
2. “Lock” the memory block by calling LocalLock. This function accepts a handle to the
memory block and returns a pointer to the memory block.
3. You can utilize the pointer to read or write memory.
4. “Unlock” the memory block by calling LocalUnlock . This function cancels the pointer to
the memory block.
5. Free the memory block by calling LocalFree. This function accepts the handle to the
memory block.

You can also replace “Local” by “Global” like GloballAlloc, GlobalLock, etc.
The above method can be further simplified by means of a flag in GlobalAlloc call,
GMEM_FIXED. If you use this flag, the return value from Global/LocalAlloc will be the pointer
to the assigned memory block, not the memory block handle. You don’t have to call Global/
LocalLock and you can pass the pointer to Global/LocalFree without calling Global/LocalUnlock
first.

Self Assessment

Fill in the blanks:
4. Local-type API calls deal with the local .................... of the process so they’re “near” memory
functions.
5. .................... function returns a handle to the requested memory block.

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