Bug report #11231
Function rand() only gives values up to ~32000
| Status: | Closed | ||
|---|---|---|---|
| Priority: | Normal | ||
| Assignee: | - | ||
| Category: | Expressions | ||
| Affected QGIS version: | master | Regression?: | No |
| Operating System: | Windows 7, 64 bit | Easy fix?: | No |
| Pull Request or Patch supplied: | No | Resolution: | end of life |
| Crashes QGIS or corrupts data: | No | Copied to github as #: | 19539 |
Description
On a spatialite layer, creating a new field with the field calculator and the expression "rand( 100000, 5000000 )" gives values of 100000 - 140000.
This seems not to be a problem on linux.
"randf()" also works properly.
The data type of the field was Integer.
QGIS was installed as 32bit.
History
#1
Updated by Giovanni Manghi about 10 years ago
- Affected QGIS version changed from 2.4.0 to master
confirmed on the latest master on Windows (qgis 32 and 64 bit). Ok on Linux.
#2
Updated by Matthias Kuhn about 10 years ago
Investigating a bit:
Visual Studio (up to 2013) has RAND_MAX defined as 0x7fff: 32767. Author's note: which seems quite stupid on a 32bit/64bit system.
(http://msdn.microsoft.com/en-us/library/2dfe3bzd.aspx)
A possibility to overcome this is to call rand() twice and bitshift/combine the values:
http://stackoverflow.com/questions/4832975/win32-higher-random-max-value
Or to use the <random> header file which is part of C++ 2011 and boost
http://msdn.microsoft.com/en-us/library/bb982398.aspx
#3
Updated by Giovanni Manghi over 7 years ago
- Easy fix? set to No
- Regression? set to No
#4
Updated by Giovanni Manghi over 5 years ago
- Resolution set to end of life
- Status changed from Open to Closed
End of life notice: QGIS 2.18 LTR
Source:
http://blog.qgis.org/2019/03/09/end-of-life-notice-qgis-2-18-ltr/