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Hello,
I am using the intrinsic for square root. I know from the Optimization manual I could use reciprocal square root and aproximation algorithm. But I need the accuracy.
The thing is that AVX shows no improvement over SSE. Intrinsics guide gave me some hints. Is it true that the square root operation is not pipeling for both SSE and AVX? At least latency and througput indicte this. I mean AVX has twice data amount per operation but a double of latency and half of througput means all combined same performance? Is it so?
My testsystem is an i5-2410M. In the intrinsics guide (I updated to the newest version) I only find latency and througput for Sandy Bridge. Has performance of this commands improved in Ivy Bridge? Could anyone explain the CPUID(s) a little bit? 06_2A means Sandy Bridge or does it not? Does this account for all Sandy Bridge CPUs (regardless of Desktop or Mobile or i3, i5, i7)?
For CPUID(s) I found: http://software.intel.com/en-us/articles/intel-architecture-and-processor-identification-with-cpuid-model-and-family-numbers
Does the intrinsics guide refer to a combination of family and model number? What about model numbers not mentioned in the intrinsics guide like Ivy Bridge?
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In the particular case where your operands can be expressed exactly in 12 bits precision, it seems that your accuracy doesn't vary among these methods. Accuracy of the sqrt reciprocal approximation varies between AMD CPU families, but I think Intel tried to keep it the same.
If you wished to test accuracy of sqrt without going through an exhaustive list of cases, you could try something like the Paranoia benchmark.
The earliest AMD families had a 14-bit approximation which would be sufficient to obtain 52 bits after 2 iterations; this has been considered at Intel but I don't know of it ever being adopted.
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Thanks for posting sqrt(x) test case.
What is this sqrt(x) implementation "User Sqrt - RTfloat"?
Do you have results for SSE sqrt(x) where x = double primitive type?
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Hi everybody, Next three test results demonstrate what the latest version of Intel C++ compiler can do...
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