Caching "One of the Keys to Happiness Is a Bad

question 6

Essay

Caching. "One of the keys to happiness is a bad memory." -Rita Mae Brown Consider the following piece of code:
int x = 0, y = 0; // The compiler puts x in r1 and y in r2. int i; // The compiler put i in r3.
int A[4096]; // A is in memory at address 0x10000
...
for (i=0;i<1024;i++) { x += A[i];
}
for (i=0;i<1024;i++) { y += A[i+2048];
}
(a) Assume that the system has a 8192-byte, direct-mapped data cache with 16-byte blocks. Assuming that the cache starts out empty, what is the series of data cache hits and misses for this snippet of code. Assume that ints are 32-bits.
(b) Assume that an iteration of a loop in which the load hits takes 10 cycles but that an iteration of a loop in which the load misses takes 100 cycles. What is the execution time of this snippet with the aforementioned cache?
(c) Repeat part A except assume that the cache is 2-way set associative with an LRU replacement policy and 16-byte sets (8-byte blocks).
(d) Repeat part B using the cache described in part C. Is the direct-mapped or the set-associative cache better?

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Definitions:

Increasing-Cost Industry

An industry where the costs of production increase as the industry expands, often due to factors like limited resources or increased prices for inputs.

Market Demand

The total demand for a product or service within a particular market, summed from all individual demands.

LAC Curve

Long-Run Average Cost curve, a graphical representation showing the minimum average cost of production at different levels of output when input prices and technology remain constant.

Constant-Cost Industry

A constant-cost industry is an industry where the costs of production, including inputs, do not change as the industry's output changes.