How to convert Delphi TDateTime to String with microsecond precision - delphi

I need to convert a TDateTime to a String with microsecond precision.
In case of millisecond precision it is possible to use formatting:
DateTimeToString(Result, 'd.m.yyyy hh:nn:ss.zzz', dateTime);
but I need three more digits (microseconds).
It is possible to take the fractional part and divide it by 1/86400/1000000 but I'm looking for more efficient way to convert it.

The accuracy of a date-time varies depending how far away from "zero" you are.
A Delphi TDateTime is actually an 8-byte floating point Double, with zero being 12/30/1899 12:00:00 am.
We can figure out the precision of a TDateTime by incrementing the floating point datetime by the smallest quantum possible:
function AddQuantumToDateTime(const dt: TDateTime): TDateTime;
var
overlay: Int64 absolute Result;
begin
Result := dt;
overlay := overlay+1;
end;
With this, we can figure out the smallest increment that a TDateTime can even handle. It varies with the date being used, as the further you are from zero, the larger the quantum amount is:
12/31/1899: ±0 ns
1/1/1900: ±0 ns
1/1/1970: ±314 ns
1/1/2000: ±629 ns
1/1/2016: ±629 ns
1/1/2038: ±629 ns
1/1/3000: ±5,029 ns
1/1/4000: ±10,058 ns
1/1/5000: ±20,117 ns
1/1/6000: ±20,117 ns
1/1/7000: ±20,117 ns
1/1/8000: ±40,233 ns
1/1/9000: ±40,233 ns
1/1/9999: ±40,233 ns
So for the time being, a DateTime can give you a resolution of about half a microsecond.
While the Windows FILETIME structure does support a resolution of 100ns, the SYSTEMTIME structure only supports down to the millisecond:
typedef struct _SYSTEMTIME {
WORD wYear;
WORD wMonth;
WORD wDayOfWeek;
WORD wDay;
WORD wHour;
WORD wMinute;
WORD wSecond;
WORD wMilliseconds;
} SYSTEMTIME, *PSYSTEMTIME;
Microsoft SQL Server's new datetime2(7) returns datetime strings with up to seven digit (100 ns) of fractional second accuracy:
SELECT CAST('20160802' AS datetime2(6)) AS TheNow
TheNow
==========================
2016-08-02 00:00:00.000000
Your question then is how to convert a TDateTime to a string that contains microsecond (billionths of a second) precision. You already have your answer:
function DateTimeToStrUs(dt: TDatetime): string;
var
us: string;
begin
//Spit out most of the result: '20160802 11:34:36.'
Result := FormatDateTime('yyyymmdd hh":"nn":"ss"."', dt);
//extract the number of microseconds
dt := Frac(dt); //fractional part of day
dt := dt * 24*60*60; //number of seconds in that day
us := IntToStr(Round(Frac(dt)*1000000));
//Add the us integer to the end:
// '20160801 11:34:36.' + '00' + '123456'
Result := Result + StringOfChar('0', 6-Length(us)) + us;
end;
Where:
DateTimeToStrUs(Now)
Returns:
20160802 11:34:36.482364

Related

Delphi FormatFloat

I have an output txtfile with some float numbers and I like to print in different formats, y try with:
FormatFloat('00000;000.0;00.00', val)
FormatFloat('00.00;000.0;00000', val)
But I take wrong outputs. What I need is:
If val < 10 then output like '00.00'
If 10 < val < 100 then output like '000.0'
If val > 100 then output like '00000'
It's a huge amount of float values, so, I need a low processing solution and I think more conditionals will slow down the application. ¿Any advice?
Thank you
Using conditional tests to sort the values into separate outputs is not going to affect performance in a significant way. The format process is far more elaborate. One important thing about optimization is to only walk that path if you can measure a performance hit in the actual code.
if (val < 10) then
s := FormatFloat('00.00',val)
else
if (val < 100) then
s := FormatFloat('000.0',val)
else
s := FormatFloat('00000',val);
Also consider using the thread-safe FormatFloat with a supplied FormatSettings variable.
I suppose that conditionals would work faster, but consider this sketch (care about out-of-range values):
const
FormatString: array[-1..2] of string = ('0.000', '0.00', '0.0', '0');
var
x: Double;
i: integer;
begin
x := 0.314;
for i := 1 to 4 do begin
Memo1.Lines.Add(FormatFloat(FormatString[Floor(Log10(x))], x));
x := x * 10;
end;
0.314
3.14
31.4
314

Getting value using percent and rounding down

I have a few values
Quantity := 5;
Quantity2 := 8;
percent :=50;
so i want
Percent of Quantity + Quantity 2
which would be like : 50% of 13 = 6.5
I done it like this
HowMuchDamage := trunc(percent*(Quantity + Quantity2)/100);
How can i make it round up?
How can i make it round down?
Floor(X) returns the highest integer less than or equal to X.
Ceil(X) returns the lowest integer greater than or equal to X.

Generate random number in a float range

How we can generate randomize number between a range in the Float numbers (in delphi xe3) ?
For example, randomize number between [0.10 to 0.90].
I need give results like:
[ 0.20 , 0.32 , 0.10 , 0.50 ]
Thanks for solutions....
Another option is to use RandomRange (returns: AFrom <= r < ATo) as follow:
RandomRange(10, 90 + 1) / 100
or
RandomRange(10, 90 + 1) * 0.01
will return numbers in the range of 0.10 to 0.90 (including 0.90)
var
float : Double;
float := Random; // Random float in range: 0 <= float < 1
float := 0.1 + float*0.8 // 0.1 <= float < 0.9
To initialize the Random number generator, make a single call to Randomizeor set the RandSeed parameter before calling the Random function for the first time.
Not doing so, generates the same sequence every time you run the program. Note however, that this sequence is not guaranteed when recompiling for another compiler version.
Try this:
function RandomRangeF(min, max: single): single;
begin
result := min + Random * (max - min);
end;
This is a bit cheeky but here goes: Depends how many numbers you want after the floating point. For example, if you want 1 number, you could generate in the 100 - 999 range and then divide by 10. Or 1000 - 9999 and divide by 100.

Calculating Hurst Exponent

Hi there =) And sorry for my English, in advance
I have a task to calculate hurst exponent by method of linear regression. And I have text description of solution. It looks very easy, but always i get values, that go out from range 0..1. Usually, value is 1.9 or something similar. Sometimes it gets negative value that is close to zero.
I have looked over code about thousand times but couldn't see a mistake.
var
max_z,min_z,x_m:real; //max and min of cumulative sum and mean value of X for every Tau
st,ss,sst,st2 :real;
Al, Herst: real;
x_vr:array of double; //a piece of array with length=tau
i, j, nach: integer;
begin
//file opening and getting values of X array are in another function
nach:=3; //initial value of tau
Setlength(ln_rs,l-nach); //length of ln(R/S) array
Setlength(ln_t,l-nach); //length of ln(tau) array
Setlength(r,l-nach); //length of R array
Setlength(s,l-nach); //length of S array
//Let's start
for tau:=nach to l do //we will change tau
begin
Setlength(x_vr,tau+1); //set new local array (length=tau)
for i:=0 to length(x_vr)-1 do
x_vr[i]:=x[i];
x_m:=Mean(x_vr); //mean value
Setlength(y,tau+1); //length of array of difference from mean value
Setlength(z,tau+1); //length of array of cumulative sum
for i:=0 to tau do
y[i]:=x_vr[i]-x_m; //difference from mean value
z[0]:=y[0];
for i:=1 to tau do //cumulative sum
for j :=i downto 0 do
z[i]:=z[i]+y[j];
max_z:=z[0];
for i:=1 to tau do //max of cumulative sum
max_z:=max(max_z,z[i]);
min_z:=z[0];
for i:=1 to tau do //min of cumulative sum
min_z:=min(min_z,z[i]);
r[tau-nach]:=max_z-min_z; //R value
s[tau-nach]:=0;
for i:=0 to tau do
s[tau-nach]:=power(y[i],2)+s[tau-nach]; //S value
s[tau-nach]:=sqrt(s[tau-nach]/(tau+1));
//new array values
ln_rs[tau-nach]:=Ln(R[tau-nach]/S[tau-nach]); // ln(R/S)
ln_t[tau-nach]:=ln(tau); // ln (tau)
end; //End of calculating
//Method of Least squares
for i:=0 to length(ln_rs)-1 do
st:=st+ln_t[i];
st:=(1/length(ln_rs))*st;
for i:=0 to length(ln_rs)-1 do
ss:=ss+ln_rs[i];
ss:=(1/length(ln_rs))*ss;
for i:=0 to length(ln_rs)-1 do
sst:=sst+ln_t[i]*ln_rs[i];
sst:=(1/length(ln_rs))*sst;
for i:=0 to length(ln_rs)-1 do
st2:=st2+ln_t[i]*ln_t[i];
st2:=(1/length(ln_rs))*st2;
Herst:=(sst-st*ss)/(st2-st*st); //coefficient of approximal function
al:=ss-st*Herst;
Thanks everybody =)
P.S.
for tau:=nach to l do
There is L, not 1. And L is Length of X array. And L>nach always besides last step, when l=nach.
P.P.S.
It works, guys. But values are not right. And they go out from range. Maybe, there is mistake in algorithm. Or maybe I skiped some step.
Last Update
It's mystic, but i only changed method of calculating array Z and it started works correctly....
Thanks all =)
First thing I see:
nach := 3;
for tau := nach to l do //w
This counts up. And because nach>1, the body of this loop won't be executed.
If you expect to count down. Use the downto variant. To count down:
for tau := nach downto l do //w
Given that the main loop (for tau) iterates from nach to l, the first four SetLength calls should set the length of l - nach + 1 instead of l - nach.
Should the line
z[i]:=z[i]+y[j];
not be
z[i]:=z[i - 1]+y[j];
?

How can I know why my program calculations and output is incorrect?

I'm working on a programming problem.
Note: This is not a student project. I am working on this for a new Quest for the website Try My Quest Dot Com, for which i am the admin.
Problem:
Jenny just started work as a programmer for Justine's Java Workshop. She is paid $10
an hour, with a few exceptions. She earns an extra $1.50 an hour for any part of a day where she works more than 8 hours, and an extra $2.50 an hour for hours beyond 40 in any one week. Also, she earns a 125% bonus for working on Saturday, and a 50% bonus for working on Sunday. The bonuses for Saturday and Sunday are computed based on the hours worked those days; they are not used to calculate any bonus for working more than 40 hours in a week. You'll be given the number of hours Jenny worked each day in a week (Sunday, Monday, etc ), and you need to compute her salary for the week. The input will be positive integers, less than or equal to 24. The output must be formatted with a dollar sign and rounded up to the nearest penny. For example, $2" and $2.136666" are wrong answers; the correct versions are $2.00" and $2.14", respectively.
Anyway, i am trying to write this in Delphi (No form project). I pass the program a command line argument - timecard.dat
input
0, 8, 8, 8, 8, 8, 0
0, 10, 10, 10, 10, 10, 0
0, 0, 8, 8, 8, 8, 8
0, 0, 0, 10, 10, 10, 10
10, 10, 10, 9, 9, 9, 9
Output
Output #1: $400.00
Output #2: $540.00
Output #3: $500.00
Output #4: $540.75
Output #5: $905.88
My Out put however is:
Output #1: $400.00
Output #2: $540.00
Output #3: $500.00
Output #4: $537.00
Output #5: $902.50
The last two output values of mine are different from the actual results. Not sure why, and the more i stare at the code, the less i see it
Can anyone tell me what i have done wrong?
program ACSL_Time_Cards;
{assumes Sunday = 1, Monday 3, etc}
uses
SysUtils,
Dialogs;
const
HourlyWage = 10.00;
OverEightWage = 1.50;
OverFortyWage = 2.50;
var
F: TextFile;
I, ArrayIndex: Integer;
WeeklyHours: Array[0..6] of Integer; //weekly hours
HourStr, LineStr: String;
TotalHours, TotalOverFortyHours, TotalOverEightHours, TotalSatHours, TotalSunHours: Integer;
TotalWages: Real;
begin
//initialize variables
TotalHours:= 0;
TotalOverEightHours:= 0;
TotalOverFortyHours:= 0;
TotalSatHours:= 0;
TotalSunHours:= 0;
TotalWages:= 0.00;
ArrayIndex:= 0;
//open file "timecard.dat" for input
if FileExists(ParamStr(1)) then
begin
AssignFile(F, ParamStr(1));
Reset(F);
//step through file and extract each line and store in hoursStr
while not EOF(F) do
begin
Readln(F, LineStr);
//step through hours string and fill Array with weekly hours
for I:= 1 to length(LineStr) do
begin
//if character is not a ',' then add it to hourStr
if LineStr[I] <> ',' then
HourStr:= HourStr + LineStr[I]
else
begin
//add HourStr to Array
WeeklyHours[ArrayIndex]:= StrToInt(HourStr);
//reset the variable
HourStr:= '';
//increment Variable
Inc(ArrayIndex);
end; //else
end; //for I:= 1 to length(HoursStr) do
//clean up by adding the last remaining one
WeeklyHours[ArrayIndex]:= StrToInt(HourStr);
//step through array and figure out overtime Daily and Weekly
for I:= Low(WeeklyHours) to High(WeeklyHours) do
begin
TotalHours:= TotalHours + WeeklyHours[I];
if WeeklyHours[I] > 8 then
TotalOverEightHours:= TotalOverEightHours + WeeklyHours[I]-8;
//get sunday hours
if I + 1 = 1 then
TotalSunHours:= TotalSunHours + WeeklyHours[I];
//get saturday hours
if I + 1 = 7 then
TotalSatHours:= TotalSatHours + WeeklyHours[I];
end;
//get total over 40 hours
if TotalHours > 40 then
TotalOverFortyHours:= TotalHours-40;
//compute Regular Hours
TotalWages:= TotalWages + TotalHours * 10.00;
//compute overtime hours
TotalWages:= TotalWages + TotalOverEightHours * 1.50;
TotalWages:= TotalWages + TotalOverFortyHours * 2.50;
//compute bonuses
TotalWages:= TotalWages + (TotalSatHours * 10.00) * 1.25;
TotalWages:= TotalWages + (TotalSunHours * 10.00) * 0.50;
ShowMessage('TotalWages: ' + FormatFloat('$0.00', TotalWages));
//reset variables
TotalWages:= 0.00;
TotalHours:= 0;
TotalOverEightHours:= 0;
TotalOverFortyHours:= 0;
TotalSatHours:= 0;
TotalSunHours:= 0;
HourStr:= '';
ArrayIndex:= 0;
end; //while not EOF(F) do
CloseFile(F);
end
else
ShowMessage('File does not exist!');
end.
I'm sure there are many ways that this could have been written better. I really am just interested in why my values different from the expected values. Thanks!
For a simple problem like this, you might want to write it out by hand and then see if your code follows the same steps you did.
For Output 4, the 125% bonus for Saturday is not including the $1.50 per hour extra after 8:
she should earn
Wed: $103 | $100 for 10 hours plus $3 for 2 hours over 8
Thu: $103 | $100 for 10 hours plus $3 for 2 hours over 8
Fri: $103 | $100 for 10 hours plus $3 for 2 hours over 8
Sat: $231.75 | ($100 for 10 hours, $3 for 2 hours over 8), $128.75 for 125% bonus
for a total of 540.75
The code would benefit from the I/O and the calculation being separated. You problems are with the calculation. I'd write it something like this:
uses
Math;
type
TDay = (
daySunday,
dayMonday,
dayTuesday,
dayWednesday,
dayThursday,
dayFriday,
daySaturday
);
TDayArray = array [TDay] of Integer;
function Wage(const Hours: TDayArray): Double;
const
BasicRate = 10.0;
DailyOvertimeRate = 1.5;
WeeklyOvertimeRate = 2.5;
DailyOvertimeThreshold = 8;
WeeklyOvertimeThreshold = 40;
DailyBonus: array [TDay] of Double = (1.5, 1.0, 1.0, 1.0, 1.0, 1.0, 2.25);
var
Day: TDay;
DailyOvertimeHours, WeeklyOvertimeHours, TotalHours: Double;
DailyPay: array [TDay] of Double;
begin
TotalHours := 0.0;
for Day := low(Day) to high(Day) do begin
TotalHours := TotalHours + Hours[Day];
DailyOvertimeHours := Max(Hours[Day]-DailyOvertimeThreshold, 0.0);
DailyPay[Day] := Hours[Day]*BasicRate;
DailyPay[Day] := DailyPay[Day] + DailyOvertimeHours*DailyOvertimeRate;
DailyPay[Day] := DailyPay[Day]*DailyBonus[Day];
end;
WeeklyOvertimeHours := Max(TotalHours-WeeklyOvertimeThreshold, 0.0);
Result := Sum(DailyPay) + WeeklyOvertimeHours*WeeklyOvertimeRate;
end;
This is still a little unpolished and I'm not very happy with the variable names for pay rates, overtime etc.
Once have such a utility function available, then putting it together with the rest of your program becomes a lot easier.
The biggest weakness in your current program is that everything is housed in one giant routine. Break it down into small pieces and you'll be able to verify those small pieces more readily than hunting for problems in a single large routine.
Find this by yourself by learning How to debug a Delphi program.
Pay atention to this parts:
Watches - you add a watch to track the values of program variables or expressions as you step over or trace into code.
Breakpoints - when pressing the F5 button or clicking on the left bar in your editor you can add a red line to your source. This line of source will have a breakpoint. When running the program, the execution will stop when it passes the source line. Now you can trace into your source by using some function keys.

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