There appear to be errors in the return types for some single precision BLAS functions in the Apple -framework accelerate library. These errors exist for both intel and arm64 hardware. Here is a small fortran program that demonstrates these errors:
program sblas
! test some single-precision blas results.
implicit none
real :: x(2)=[3.,4.], y(2)=[1.,1.]
complex :: w(2)=[(4.,3.),(3.,4.)], z(2)=[(5.,6.),(7.,8.)]
real, external :: sdot, sdsdot, snrm2, scnrm2, sasum, scasum
complex, external :: cdotu, cdotc
character(*), parameter :: cfmt='(*(g0.4,1x))'
write(*,cfmt) 'sdot=', sdot(2,x,1,y,1), 'should be 7.000'
write(*,cfmt) 'sdsdot=', sdsdot(2,0.0,x,1,y,1), 'should be 7.000'
write(*,cfmt) 'snrm2=', snrm2(2,x,1), 'should be 5.000'
write(*,cfmt) 'scnrm2=', scnrm2(2,w,1), 'should be 7.071'
write(*,cfmt) 'sasum=', sasum(2,x,1), 'should be 7.000'
write(*,cfmt) 'scasum=', scasum(2,w,1), 'should be 14.00'
write(*,cfmt) 'cdotu=', cdotu(2,w,1,z,1), 'should be -9.000 91.00'
write(*,cfmt) 'cdotc=', cdotc(2,w,1,z,1), 'should be 91.00 5.000'
end program sblas
The correct output is:
$ ifort -L${MKLROOT}/lib -Wl,-rpath,${MKLROOT}/lib -lmkl_intel_lp64 -lmkl_intel_thread -lmkl_core -liomp5 -lpthread sblas.f90 && a.out
sdot= 7.000 should be 7.000
sdsdot= 7.000 should be 7.000
snrm2= 5.000 should be 5.000
scnrm2= 7.071 should be 7.071
sasum= 7.000 should be 7.000
scasum= 14.00 should be 14.00
cdotu= -9.000 91.00 should be -9.000 91.00
cdotc= 91.00 5.000 should be 91.00 5.000
With the Apple -framework accelerate library, I get
$ ifort -framework accelerate sblas.f90 && a.out
sdot= .000 should be 7.000
sdsdot= .000 should be 7.000
snrm2= .000 should be 5.000
scnrm2= .000 should be 7.071
sasum= .000 should be 7.000
scasum= .000 should be 14.00
cdotu= -9.000 91.00 should be -9.000 91.00
cdotc= 91.00 5.000 should be 91.00 5.000
The REAL results are incorrect, while the single precision COMPLEX results are alright. Some experimentation reveals that the problem is that the function return values are REAL(8) rather than the correct REAL.
If I try gfortran instead of ifort, I get:
$ gfortran -framework accelerate sblas.f90 && a.out
sdot= 0.000 should be 7.000
sdsdot= 0.000 should be 7.000
snrm2= 0.000 should be 5.000
scnrm2= 0.000 should be 7.071
sasum= 0.000 should be 7.000
scasum= 0.000 should be 14.00
Program received signal SIGSEGV: Segmentation fault - invalid memory reference.
Backtrace for this error:
#0 0x10af498be
#1 0x10af48a9d
#2 0x7fff207ced7c
#3 0x7fff2105dfc8
#4 0x10af37bc1
#5 0x10af37d7e
Segmentation fault: 11
Here, not even the single precision COMPLEX results are returned correctly.
Presumably, the accelerate library passes its regression tests. This implies that the regression tests have the incorrect return types declared for these functions. Thus to correct this error, both the library and its regression tests must be corrected together.