A communication fabric in a parallel computer has the structure of a binary tree. Processors are connected to the leaf nodes and memory system lock hardware is connected to the root. Each internal node in the fabric has the ability to compare simultaneous lock requests from its two child nodes for equality. If the requests are for the same lock and for read-access to a memory location, the fabric node will combine the two requests into one unified request to pass up the tree and remember the combined access.  When the memory system responds to the read access, a fabric internal node will, in response to a match with a remembered combined request, replicate the response to “un-combine” and pass the response to both of its child nodes. How does this Combining Tree communication fabric improve parallelism for read-access to lock-protected values in memory

Consider a 1GByte memory that can be managed by either a bitmap or a linked list. The memory allocation unit is in units of n bytes, which is some power of 2. Memory in the linked list is either marked as free or used (i.e. holes and segments). Assume that each node in the list requires 64 total bits (including a memory address, a length, and a pointer to the next linked list element). Also, make the (unrealistic) assumption that holes and segments are all 32KB (215 bytes) and that they alternate so that there is no coalescing of adjacent holes. It also means that each linked list element covers either a 32KB hole or a 32KB segment. Determine how much memory each data structure uses (the bitmap will be in terms of n)

A Pregel worker: a) Contacts the master for a set of vertices that have not yet been processed in a given superstep and calls the Compute() method on each vertex. b) Is responsible for a single vertex of a graph, calling the Compute() method on that vertex if it is active. c) Is allocated a single partition and runs a thread for each vertex of a graph that loops calling a Compute() method as long as the vertex is active. d) Runs a thread for each partition of a graph, with each thread calling a Compute() method as it iterates through each active vertex.

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Turn on the Non-executable Stack Protection Operating systems used to allow executable stacks, but this has now changed: In Ubuntu OS, the binary images of programs (and shared libraries) must declare whether they require executable stacks or not, i.e., they need to mark a field in the program header. Kernel or dynamic linker uses this marking to decide whether to make the stack of this running program executable or non-executable. This marking is done automatically by the gcc, which by default makes stack non-executable. We can specifically make it nonexecutable using the "-z noexecstack" flag in the compilation. In our previous tasks, we used "-z execstack" to make stacks executable. In this task, we will make the stack non-executable. We will do this experiment in the shellcode folder. The callshellcode program puts a copy of shellcode on the stack, and then executes the code from the stack. Please recompile call shellcode.c into a32.out and a64.out, without the "-z execstack"…