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' 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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