' MAT is slower than direct multiplication

'

' To my surprise MAT seems to calculate slower than direct multiplication

' in this particular example. Is this a generally recognized fact?

' If so what is the explanation?

'

' To my surprise MAT seems to calculate slower than direct multiplication

' in this particular example. Is this a generally recognized fact?

' If so what is the explanation?

Code:

' MAT is slower than direct multiplication ' ' To my surprise MAT seems to calculate slower than direct multiplication ' in this particular example. Is this a generally recognized fact? ' If so what is the explanation? #COMPILE EXE #REGISTER NONE #DIM ALL ' #INCLUDE "WIN32API.INC" ' ' The function below is taken from my code in this thread: ' http://www.powerbasic.com/support/pbforums/showthread.php?t=24258 FUNCTION CurrentTimePointInSeconds AS DOUBLE ' This function returns the number of seconds since midnight ' as a Double-precision floating-point value. STATIC PerfFreq AS QUAD, Res AS LONG, Prec AS LONG, First AS LONG, TimeCorrection AS DOUBLE LOCAL t1 AS QUAD, ta AS DOUBLE ' IF ISFALSE First THEN ' Get, in counts per second, the current performance-counter frequency ' if supported by your hardware. Res = QueryPerformanceFrequency(PerfFreq) ' ' Determine Precision IF Res THEN Prec = CEIL(LOG10(PerfFreq)) QueryPerformanceCounter t1 ta = ROUND(CDBL(t1) / CDBL(PerfFreq), Prec) ' Find time correction to obtain number of seconds past midnight. TimeCorrection = TIMER - ta ' FUNCTION = ta + TimeCorrection First = %TRUE : EXIT FUNCTION ELSE Prec = 2 ' Precision of TIMER is only about 1/18th of a second. END IF First = %TRUE END IF ' Measure current time IF Res THEN ' if possible use this: QueryPerformanceCounter t1 FUNCTION = ROUND(CDBL(t1) / CDBL(PerfFreq), Prec) + TimeCorrection ELSE ' else use the built-in timer ta = TIMER FUNCTION = ROUND(ta, Prec) END IF ' END FUNCTION ' FUNCTION PBMAIN LOCAL t1 AS DOUBLE, t2 AS DOUBLE LOCAL tx AS STRING LOCAL i&,j&,k&, m& LOCAL fa AS DOUBLE DIM B(1 TO 3) AS LOCAL SINGLE ' Input vector DIM C(1 TO 4, 1 TO 3) AS LOCAL SINGLE ' Transformation matrix DIM A(1 TO 4) AS LOCAL SINGLE ' Resulting output vector ' DATA 4.1256, 0.3879, 1.35566 : ' vector B ' ' tx = "vector B() = " + $CRLF tx= tx +$CRLF+$CRLF + "Matrix C() = " + $CRLF DATA 1.34566, -3.2345, 0.23445, 2.2333 : ' matrix C - row 1 DATA 2.27654, 5.98765, 3.12334, -1.54333 : ' matrix C - row 2 DATA 4.23555, 6.23444, 1.25552, 8.6654 : ' matrix C - row 3 ' ' Read arrays ' tx = "vector B() = " + $CRLF FOR i = 1 TO 3 INCR k B(i) = VAL(READ$(k)) tx = tx + STR$(B(i))+" " NEXT tx= tx +$CRLF+$CRLF + "Matrix C() = " + $CRLF FOR i = 1 TO 3 FOR j = 1 TO 4 INCR k C(j,i) = VAL(READ$(k)) tx=tx+STR$(C(j,i))+" " NEXT tx=tx+$CRLF NEXT ' tx = tx +$CRLF+$CRLF +"A() = C() * B()" ' Do direct calculation ' ' Measure first time t1 = CurrentTimePointInSeconds FOR m = 1 TO 1000000 ' Do calculation 1 mill. times FOR j = 1 TO 4 ' Column A(j) = 0! FOR k = 1 TO 3 ' Row A(j) = A(j) + B(k) * C(j,k) NEXT k NEXT j NEXT ' Measure second time t2 = CurrentTimePointInSeconds tx = tx +$CRLF+$CRLF+"Direct Calculation:"+$CRLF+$CRLF+"Time 1: " + FORMAT$(t1) + " seconds past midnight" + $CRLF tx = tx + "Time 2: " + FORMAT$(t2) + " seconds past midnight" + $CRLF + $CRLF tx = tx + "Time interval in seconds is: " + FORMAT$(t2 - t1, "######.#########") fa = t2 - t1 ' ' t1 = CurrentTimePointInSeconds ' FOR m = 1 TO 1000000 ' Do calculation 1 mill. times ' ' Do calculation using MAT ' MAT A() = C() * B() NEXT t2 = CurrentTimePointInSeconds ' tx = tx + $CRLF+$CRLF+$CRLF+"MAT Calculation:"+$CRLF+$CRLF+"Time 1: " + FORMAT$(t1) + " seconds past midnight" + $CRLF tx = tx + "Time 2: " + FORMAT$(t2) + " seconds past midnight" + $CRLF + $CRLF tx = tx + "Time interval in seconds is: " + FORMAT$(t2 - t1, "######.#########") fa = (t2 - t1)/fa tx=tx+$CRLF+$CRLF+"Thus MAT is "+FORMAT$(fa, "######.###")+" times slower that direct calculation." MSGBOX tx, %MB_ICONINFORMATION, "Multiplication Time" ' END FUNCTION

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