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Unformatted text preview: cation, even though the number of cycles for the functional units are comparable. On an IA32 processor, all floating-point operations are performed in extended 80-bit) precision, and the floating-point registers store values in this format. Only when the value in a register is written to memory is it converted to 32-bit (float) or 64-bit (double) format. Examining the data used for our measurements, the source of the problem becomes clear. The measurements were performed on a vector of length 1024 having element equal to · ½. Hence, we are attempting to compute ½¼¾ , which is approximately ¢ ½¼¾ ¿ . Such a large number can be represented in the extended-precision floating-point format (it can represent numbers up to around ½¼ ¿¾ ), but it far exceeds what can be represented as a single precision (up to around ½¼¿ ) or double precision (up to around ½¼¿¼ ). The single precision case overflows when we reach ¿ , while the double precision case overflows when we reach ½ ½. Once we reach this point, every execution of the statement *dest = *dest OPER val; in the inner loop of combine3 requir...
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This note was uploaded on 09/02/2010 for the course ELECTRICAL 360 taught by Professor Schultz during the Spring '10 term at BYU.

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