Re: [sqlite] How to input a double num?
On Fri, 30 Oct 2009 02:47:37 -0700 (PDT), liubin liu <7101...@sina.com> wrote: > Thank you! > > I mayn't need the high precision like > "212345678901234567890123456.988290112". Indeed, you don't. In a previous message you said: >> The project is on power-measurement. So there >> are some big nums with high precision. I know of no power-measurement with such high precision. 6 or 7 significant digits is the best you can get in that field. As in "2123456.0" That a huge accuracy, think of one dollar on a few million. -- ( Kees Nuyt ) c[_] ___ sqlite-users mailing list sqlite-users@sqlite.org http://sqlite.org:8080/cgi-bin/mailman/listinfo/sqlite-users
Re: [sqlite] How to input a double num?
Thank you! I mayn't need the high precision like "212345678901234567890123456.988290112". John Crenshaw-2 wrote: > >> May I use sqlite3_bind_double() and sqlite3_prepare_v2() to solve the >> problem. > > That won't fix it. Your number is too large to fit in any native data > type. Even the plain math inside your own program won't work right, > because the precision of the number is limited at the C level, not the > SQLite or printf level. > > You'll need an arbitrary precision math library, sqlite3_bind_blob(), > and sqlite3_prepare_v2(). You can't use sqlite3_bind_double() because > your number is too big for a double. > > FYI, those arbitrary precision libraries are brutes, so brace yourself. > > John > ___ > sqlite-users mailing list > sqlite-users@sqlite.org > http://sqlite.org:8080/cgi-bin/mailman/listinfo/sqlite-users > > -- View this message in context: http://old.nabble.com/How-to-input-a-double-num--tp26105457p26127343.html Sent from the SQLite mailing list archive at Nabble.com. ___ sqlite-users mailing list sqlite-users@sqlite.org http://sqlite.org:8080/cgi-bin/mailman/listinfo/sqlite-users
Re: [sqlite] How to input a double num?
> May I use sqlite3_bind_double() and sqlite3_prepare_v2() to solve the > problem. That won't fix it. Your number is too large to fit in any native data type. Even the plain math inside your own program won't work right, because the precision of the number is limited at the C level, not the SQLite or printf level. You'll need an arbitrary precision math library, sqlite3_bind_blob(), and sqlite3_prepare_v2(). You can't use sqlite3_bind_double() because your number is too big for a double. FYI, those arbitrary precision libraries are brutes, so brace yourself. John ___ sqlite-users mailing list sqlite-users@sqlite.org http://sqlite.org:8080/cgi-bin/mailman/listinfo/sqlite-users
Re: [sqlite] How to input a double num?
Thanks a lot for every reply.
The num is just random num. The project is on power-measurement. So there
are some big nums with high precision.
May I use sqlite3_bind_double() and sqlite3_prepare_v2() to solve the
problem.
liubin liu wrote:
>
> Now I use the sqlite3_mprintf() and the "%f" to get the double num. My
> code is below.
>
> Now there is a num like "212345678901234567890123456.988290112". With the
> way of "sqlite3_mprintf()" and "%f", the num is cut to
> "2123456789012346000.00".
>
>
> How to input the num "212345678901234567890123456.988290112"?
>
>
> code_
>
> ...
> char *query_format = "INSERT OR REPLACE INTO pow_value_st (id, valid,
> powervalue_1, powervalue_2) VALUES (%d, %d, %f, %f)";
> char *query_string = NULL;
> query_string = sqlite3_mprintf (query_format, index, tc->valid,
> tc->powervalue[0], tc->powervalue[1]);
> printf ("%s\n", query_string);
> ...
>
>
>
> PS:
> the columns of powervalue_1 and powervalue_2 are defined as DOUBLE type:
> CREATE TABLE pow_value_st (id INTEGER PRIMARY KEY, valid CHAR(1),
> powervalue_1 DOUBLE, powervalue_2 DOUBLE );
>
--
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Re: [sqlite] How to input a double num?
> He's probably measuring the number of atoms in a city or something. LOL. Actually my bet is that field of the project has more to do with number theory. That's the only likely way to get a number that large with such high precision. John ___ sqlite-users mailing list sqlite-users@sqlite.org http://sqlite.org:8080/cgi-bin/mailman/listinfo/sqlite-users
Re: [sqlite] How to input a double num?
On 29 Oct 2009, at 12:38pm, Griggs, Donald wrote: > Regarding: How to input the num > "212345678901234567890123456.988290112"? > > > Purely curious, if it's not confidential -- how are you acquiring > numbers of such precision? > > If these are measurements, I'm just awed by the precision the device > is > achieving. The number of atoms in our planet is around 10^50. So with 34 digits of accuracy that number is discussing something which has a volume which is around one 10^5th the radius of our planet. He's probably measuring the number of atoms in a city or something. Simon. ___ sqlite-users mailing list sqlite-users@sqlite.org http://sqlite.org:8080/cgi-bin/mailman/listinfo/sqlite-users
Re: [sqlite] How to input a double num?
Regarding: How to input the num "212345678901234567890123456.988290112"? Purely curious, if it's not confidential -- how are you acquiring numbers of such precision? If these are measurements, I'm just awed by the precision the device is achieving. If instead these numbers represent something other than a measurement, you might want to consider storing them in a different form. Donald Griggs ___ sqlite-users mailing list sqlite-users@sqlite.org http://sqlite.org:8080/cgi-bin/mailman/listinfo/sqlite-users
Re: [sqlite] How to input a double num?
You cannot store 212345678901234567890123456.988290112 using IEEE a 8 byte
double precision. You cannot do this even with a 16 byte (long double - which
for x86 architectures is actually 80-bit extended precision - only 64 bit for
mantissa; is not the quadruple precision).
If you care about precision, then don't use regular floating point operations,
use a library implementing arbitrary precision operations (ex.
http://gmplib.org/). You can then store the numbers as blobs. If you need to
use these columns in expressions for queries ... well, is not straightforward,
but it can be done with sqlite. Of course, it won't be as efficient. Or you can
store them as strings and do some tricks.
On the other hand, I see that these columns are named powervalue_1 and 2,
suggesting that they are the result of some form of pow - you can store then
the arguments for pow, if this fit your needs..
I'm curious, how did you get the number 212345678901234567890123456.988290112 ?
-ic
--- On Wed, 10/28/09, liubin liu <7101...@sina.com> wrote:
> From: liubin liu <7101...@sina.com>
> Subject: [sqlite] How to input a double num?
> To: sqlite-users@sqlite.org
> Date: Wednesday, October 28, 2009, 9:48 PM
>
> Now I use the sqlite3_mprintf() and the "%f" to get the
> double num. My code
> is below.
>
> Now there is a num like
> "212345678901234567890123456.988290112". With the
> way of "sqlite3_mprintf()" and "%f", the num is cut to
> "2123456789012346000.00".
>
>
> How to input the num
> "212345678901234567890123456.988290112"?
>
>
> code_
>
> ...
> char *query_format = "INSERT OR REPLACE INTO
> pow_value_st (id, valid,
> powervalue_1, powervalue_2) VALUES (%d, %d, %f, %f)";
> char *query_string = NULL;
> query_string = sqlite3_mprintf (query_format,
> index, tc->valid,
> tc->powervalue[0], tc->powervalue[1]);
> printf ("%s\n", query_string);
> ...
>
> --
> View this message in context:
> http://www.nabble.com/How-to-input-a-double-num--tp26105457p26105457.html
> Sent from the SQLite mailing list archive at Nabble.com.
>
> ___
> sqlite-users mailing list
> sqlite-users@sqlite.org
> http://sqlite.org:8080/cgi-bin/mailman/listinfo/sqlite-users
>
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Re: [sqlite] How to input a double num?
liubin liu wrote: > Now I use the sqlite3_mprintf() and the "%f" to get the double num. My code > is below. > > Now there is a num like "212345678901234567890123456.988290112". With the > way of "sqlite3_mprintf()" and "%f", the num is cut to > "2123456789012346000.00". > > > How to input the num "212345678901234567890123456.988290112"? double has 53 bits to represent the mantissa. This is good for 15-16 decimal digits, which is what you see. You can't possibly hope to accurately represent 36 significant digits in a double - even at 3 bits per digit, that would require at least 14 bytes, and double is only 8 bytes large. See also http://dlc.sun.com/pdf/800-7895/800-7895.pdf Igor Tandetnik ___ sqlite-users mailing list sqlite-users@sqlite.org http://sqlite.org:8080/cgi-bin/mailman/listinfo/sqlite-users
Re: [sqlite] How to input a double num?
liubin liu wrote: > Now I use the sqlite3_mprintf() and the "%f" to get the double num. My code > is below. > > Now there is a num like "212345678901234567890123456.988290112". With the > way of "sqlite3_mprintf()" and "%f", the num is cut to > "2123456789012346000.00". > > > How to input the num "212345678901234567890123456.988290112"? You can't. A double only has 53 bits (about 16 decimal digits) of precision. ___ sqlite-users mailing list sqlite-users@sqlite.org http://sqlite.org:8080/cgi-bin/mailman/listinfo/sqlite-users
Re: [sqlite] How to input a double num?
Bad plan. Use prepared statements and bind. Otherwise you're going to
create SQL injection vulnerabilities. Prepared statements are faster and
easier to read anyway.
John
-Original Message-
From: sqlite-users-boun...@sqlite.org
[mailto:sqlite-users-boun...@sqlite.org] On Behalf Of liubin liu
Sent: Wednesday, October 28, 2009 10:49 PM
To: sqlite-users@sqlite.org
Subject: [sqlite] How to input a double num?
Now I use the sqlite3_mprintf() and the "%f" to get the double num. My
code
is below.
Now there is a num like "212345678901234567890123456.988290112". With
the
way of "sqlite3_mprintf()" and "%f", the num is cut to
"2123456789012346000.00".
How to input the num "212345678901234567890123456.988290112"?
code_
...
char *query_format = "INSERT OR REPLACE INTO pow_value_st (id,
valid,
powervalue_1, powervalue_2) VALUES (%d, %d, %f, %f)";
char *query_string = NULL;
query_string = sqlite3_mprintf (query_format, index, tc->valid,
tc->powervalue[0], tc->powervalue[1]);
printf ("%s\n", query_string);
...
--
View this message in context:
http://www.nabble.com/How-to-input-a-double-num--tp26105457p26105457.htm
l
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[sqlite] How to input a double num?
Now I use the sqlite3_mprintf() and the "%f" to get the double num. My code
is below.
Now there is a num like "212345678901234567890123456.988290112". With the
way of "sqlite3_mprintf()" and "%f", the num is cut to
"2123456789012346000.00".
How to input the num "212345678901234567890123456.988290112"?
code_
...
char *query_format = "INSERT OR REPLACE INTO pow_value_st (id, valid,
powervalue_1, powervalue_2) VALUES (%d, %d, %f, %f)";
char *query_string = NULL;
query_string = sqlite3_mprintf (query_format, index, tc->valid,
tc->powervalue[0], tc->powervalue[1]);
printf ("%s\n", query_string);
...
--
View this message in context:
http://www.nabble.com/How-to-input-a-double-num--tp26105457p26105457.html
Sent from the SQLite mailing list archive at Nabble.com.
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