* Program: Stream * Programmer: John D. McCalpin * Revision: 4.1, June 4, 1996 * * This program measures memory transfer rates in MB/s for simple * computational kernels coded in Fortran. These numbers reveal the * quality of code generation for simple uncacheable kernels as well * as showing the cost of floating-point operations relative to memory * accesses. * *========================================================================= * INSTRUCTIONS: * 1) Stream requires a cpu timing function called second(). * A sample is shown below. This is unfortunately rather * system dependent. The code attempts to determine the * granularity of the clock to help interpret the results. * For dedicated or parallel runs, you might want to comment * these out and compile/link with "wallclock.c". * 2) Stream requires a good bit of memory to run. * Adjust the Parameter 'N' in the main program to give * a 'timing calibration' of at least 20 clicks. * This will provide rate estimates that should be good to * about 5% precision. * ------------------------------------------------------------ * Note that you are free to use any array length and offset * that makes each array larger than the last-level cache. * The intent is to determine the *best* sustainable bandwidth * available with this simple coding. Of course, lower values * are usually fairly easy to obtain on cached machines, but * by keeping the test to the *best* results, the answers are * easier to interpret. * You may put the arrays in common or not, at your discretion. * There is a commented-out COMMON statement below. * ------------------------------------------------------------ * 3) Compile the code with full optimization. Many compilers * generate unreasonably bad code before the optimizer tightens * things up. If the results are unreasonably good, on the * other hand, the optimizer might be too smart for me * Please let me know if this happens. * 4) Mail the results to mccalpin@cs.virginia.edu * Be sure to include: * a) computer hardware model number and software revision * b) the compiler flags * c) all of the output from the test case. * * Thanks *========================================================================= * SUBROUTINE stream(n,a,b,c) IMPLICIT NONE C .. Parameters .. INTEGER*8 n INTEGER offset,ndim,ntimes,npercpu PARAMETER (ntimes=5) C .. C .. Local Scalars .. DOUBLE PRECISION dummy,scalar,t,sum1,sum2,sum3 INTEGER i,j,k,nbpw,quantum,ncpu,jstart C .. C .. Local Arrays .. DOUBLE PRECISION maxtime(4),mintime(4),rmstime(4), $ times(4,ntimes) INTEGER bytes(4) CHARACTER label(4)*11 C .. C .. External Functions .. DOUBLE PRECISION second INTEGER checktick,realsize EXTERNAL second,checktick,realsize C .. C .. Intrinsic Functions .. C INTRINSIC dble,max,min,nint,sqrt C .. C .. Arrays in Common .. DOUBLE PRECISION a(*),b(*),c(*) C .. C .. Common blocks .. * COMMON a,b,c,d C .. C .. Data statements .. DATA rmstime/4*0.0D0/,mintime/4*1.0D+36/,maxtime/4*0.0D0/ DATA label/'Copy: ','Scale: ','Add: ', $ 'Triad: '/ DATA bytes/2,2,3,3/,dummy/0.0d0/ C .. * --- SETUP --- determine precision and check timing --- ncpu = num_parthds() npercpu = n/ncpu PRINT *,'Number of Threads = ',ncpu nbpw = realsize() WRITE (*,FMT=9010) 'Array size = ',n WRITE (*,FMT=9010) 'Offset = ',offset WRITE (*,FMT=9020) 'The total memory requirement is ', $ 3*nbpw*n/ (1024*1024),' MB' WRITE (*,FMT=9030) 'You are running each test ',ntimes,' times' WRITE (*,FMT=9030) 'The *best* time for each test is used' !$OMP PARALLEL DO DO 10 j = 1,n a(j) = 1.0d0 b(j) = 2.0D0 c(j) = 0.0D0 10 CONTINUE t = second(dummy) !$OMP PARALLEL DO DO 20 j = 1,n a(j) = 2.0d0*a(j) 20 CONTINUE t = second(dummy) - t PRINT *,'----------------------------------------------------' quantum = checktick() WRITE (*,FMT=9000) $ 'Your clock granularity/precision appears to be ',quantum, $ ' microseconds' PRINT *,'The tests below will each take a time on the order ' PRINT *,'of ',nint(t*1d6),' microseconds' PRINT *,' (= ',nint((t*1d6)/quantum),' clock ticks)' PRINT *,'Increase the size of the arrays if this shows that' PRINT *,'you are not getting at least 20 clock ticks per test.' PRINT *,'----------------------------------------------------' PRINT *,'WARNING -- The above is only a rough guideline.' PRINT *,'For best results, please be sure you know the' PRINT *,'precision of your system timer.' PRINT *,'----------------------------------------------------' * --- MAIN LOOP --- repeat test cases NTIMES times --- D CALL pminit(6) scalar = 1.5d0*a(1) DO 70 k = 1,ntimes t = second(dummy) D CALL pmstart() * a(1) = t !$OMP PARALLEL DO DO i=1,ncpu jstart = nint(dble(i-1)/dble(ncpu) * n) + 1 CALL stream_copy(c(jstart),a(jstart),npercpu) END DO D CALL pmstop() t = second(dummy) - t * c(n) = t times(1,k) = t D CALL pmprint() t = second(dummy) * c(1) = t !$OMP PARALLEL DO DO i=1,ncpu jstart = nint(dble(i-1)/dble(ncpu) * n) + 1 CALL stream_scale(b(jstart),c(jstart),scalar,npercpu) END DO t = second(dummy) - t * b(n) = t times(2,k) = t t = second(dummy) * a(1) = t !$OMP PARALLEL DO DO i=1,ncpu jstart = nint(dble(i-1)/dble(ncpu) * n) + 1 CALL stream_add (c(jstart),a(jstart),b(jstart),npercpu) END DO t = second(dummy) - t * c(n) = t times(3,k) = t t = second(dummy) * b(1) = t !$OMP PARALLEL DO DO i=1,ncpu jstart = nint(dble(i-1)/dble(ncpu) * n) + 1 CALL stream_triad (a(jstart),b(jstart),c(jstart),scalar, $ npercpu) END DO t = second(dummy) - t * a(n) = t times(4,k) = t 70 CONTINUE * --- SUMMARY --- DO 90 k = 1,ntimes DO 80 j = 1,4 rmstime(j) = rmstime(j) + times(j,k)**2 mintime(j) = min(mintime(j),times(j,k)) maxtime(j) = max(maxtime(j),times(j,k)) * print *,k,j,times(j,k) 80 CONTINUE 90 CONTINUE WRITE (*,FMT=9040) DO 100 j = 1,4 rmstime(j) = sqrt(rmstime(j)/dble(ntimes)) WRITE (*,FMT=9050) label(j),n*bytes(j)*nbpw/mintime(j)/1.0D6, $ rmstime(j),mintime(j),maxtime(j) 100 CONTINUE sum1 = 0.0d0 sum2 = 0.0d0 sum3 = 0.0d0 !$OMP PARALLEL DO REDUCTION(+:sum1,sum2,sum3) DO 110 j = 1,n sum1 = sum1 + a(j) sum2 = sum2 + b(j) sum3 = sum3 + c(j) 110 CONTINUE PRINT *,'Sum of a is = ',sum1 PRINT *,'Sum of b is = ',sum2 PRINT *,'Sum of c is = ',sum3 9000 FORMAT (1x,a,i6,a) 9010 FORMAT (1x,a,i10) 9020 FORMAT (1x,a,i4,a) 9030 FORMAT (1x,a,i3,a,a) 9040 FORMAT ('Function',5x,'Rate (MB/s) RMS time Min time Max time' $ ) 9050 FORMAT (a,4 (f10.4,2x)) END *------------------------------------- * INTEGER FUNCTION dblesize() * * A semi-portable way to determine the precision of DOUBLE PRECISION * in Fortran. * Here used to guess how many bytes of storage a DOUBLE PRECISION * number occupies. * INTEGER FUNCTION realsize() * IMPLICIT NONE C .. Local Scalars .. DOUBLE PRECISION result,test INTEGER j,ndigits C .. C .. Local Arrays .. DOUBLE PRECISION ref(30) C .. C .. External Subroutines .. EXTERNAL confuse C .. C .. Intrinsic Functions .. INTRINSIC abs,acos,log10,sqrt C .. C Test #1 - compare single(1.0d0+delta) to 1.0d0 10 DO 20 j = 1,30 ref(j) = 1.0d0 + 10.0d0** (-j) 20 CONTINUE DO 30 j = 1,30 test = ref(j) ndigits = j CALL confuse(test,result) IF (test.EQ.1.0D0) THEN GO TO 40 END IF 30 CONTINUE GO TO 50 40 WRITE (*,FMT='(a)') $ '----------------------------------------------' WRITE (*,FMT='(1x,a,i2,a)') 'Double precision appears to have ', $ ndigits,' digits of accuracy' IF (ndigits.LE.8) THEN realsize = 4 ELSE realsize = 8 END IF WRITE (*,FMT='(1x,a,i1,a)') 'Assuming ',realsize, $ ' bytes per DOUBLE PRECISION word' WRITE (*,FMT='(a)') $ '----------------------------------------------' RETURN 50 PRINT *,'Hmmmm. I am unable to determine the size.' PRINT *,'Please enter the number of Bytes per DOUBLE PRECISION', $ ' number : ' READ (*,FMT=*) realsize IF (realsize.NE.4 .AND. realsize.NE.8) THEN PRINT *,'Your answer ',realsize,' does not make sense.' PRINT *,'Try again.' PRINT *,'Please enter the number of Bytes per ', $ 'DOUBLE PRECISION number : ' READ (*,FMT=*) realsize END IF PRINT *,'You have manually entered a size of ',realsize, $ ' bytes per DOUBLE PRECISION number' WRITE (*,FMT='(a)') $ '----------------------------------------------' END SUBROUTINE confuse(q,r) * IMPLICIT NONE C .. Scalar Arguments .. DOUBLE PRECISION q,r C .. C .. Intrinsic Functions .. INTRINSIC cos C .. r = cos(q) RETURN END * A semi-portable way to determine the clock granularity * Adapted from a code by John Henning of Digital Equipment Corporation * INTEGER FUNCTION checktick() * IMPLICIT NONE C .. Parameters .. INTEGER n PARAMETER (n=20) C .. C .. Local Scalars .. DOUBLE PRECISION dummy,t1,t2 INTEGER i,j,jmin C .. C .. Local Arrays .. DOUBLE PRECISION timesfound(n) C .. C .. External Functions .. DOUBLE PRECISION second EXTERNAL second C .. C .. Intrinsic Functions .. INTRINSIC max,min,nint C .. i = 0 dummy = 0.0d0 t1 = second(dummy) 10 t2 = second(dummy) IF (t2.EQ.t1) GO TO 10 t1 = t2 i = i + 1 timesfound(i) = t1 IF (i.LT.n) GO TO 10 jmin = 1000000 DO 20 i = 2,n j = nint((timesfound(i)-timesfound(i-1))*1d6) jmin = min(jmin,max(j,0)) 20 CONTINUE IF (jmin.GT.0) THEN checktick = jmin ELSE PRINT *,'Your clock granularity appears to be less ', $ 'than one microsecond' checktick = 1 END IF RETURN * PRINT 14, timesfound(1)*1d6 * DO 20 i=2,n * PRINT 14, timesfound(i)*1d6, * & nint((timesfound(i)-timesfound(i-1))*1d6) * 14 FORMAT (1X, F18.4, 1X, i8) * 20 CONTINUE END real*8 function second(dummy) real*8 dummy,rtc external rtc second = rtc() end