topic vdSqrt (64-bit Windows) throws illegal instruction on certain C in Intel® oneAPI Math Kernel Library

vdSqrt (64-bit Windows) throws illegal instruction on certain CPUS (MKL Update 4)

AndrewC — Tue, 15 Jun 2010 18:12:20 GMT

Every call to 64-bit vdSqrt throws an illegal instruction on an Intel U7300 CPU ( a ULV core 2 duo variant ).
Is this fixed in Update 5?
The 32-bit version of MKL has no such problem, nor does the problem surface on a number of 64-bit desktop Intel CPU variants we use for QA.

[bash]
e.g. 


	double a[N_SQRT];
	for (int i=0;i=i*i;
	double b[N_SQRT];
	vdSqrt(4,a,b);
[/bash]

vdSqrt (64-bit Windows) throws illegal instruction on certain C

AndrewC — Tue, 15 Jun 2010 21:47:03 GMT

I downloaded MKL Update 5 and this bug has been fixed. It would be nice if the Update 5 release notes had mentioned this - there are some references to VML problems being fixed, but no specific reference to vdSqrt

vdSqrt (64-bit Windows) throws illegal instruction on certain C

TimP — Wed, 16 Jun 2010 19:00:55 GMT

It looks like the older version selected the wrong instruction set, due to mistake in identifying your CPU. That bug would not be specific to vdSqrt.

vdSqrt (64-bit Windows) throws illegal instruction on certain C

Gennady_F_Intel — Thu, 17 Jun 2010 10:40:34 GMT

Tim right,

this is MKL's dispatching ptoblem "Illegal instruction Intel Core2 Duo CPU E8400". It has been disscussed here. The problem has been fixed in Update5.

We memtioned about that in MKL 10.2 Fix list as

DPD200090101

Illegal instruction Intel Core2 Duo CPU E8400 for VML function

--Gennady

vdSqrt (64-bit Windows) throws illegal instruction on certain C

AndrewC — Thu, 17 Jun 2010 22:14:26 GMT

The bug fix description should have said something like , in big red letters!!

"Many (all?) VML functions on (many types of ?) Intel Core2 Duo CPUs may fail with illegal instruction"

You will note my problem machine is not a E8400