Overview

Hash tables are a new data structure in SAS 9.

This sample runs in SAS 9.2 phase 1 and later

The size and composition of the hash table is determined at execution time.

The entire hash table should fit into *real* memory. If the hash table is too large, paging will start and cause performance to deteriorate significantly.

Reasons to use a hash table:

• Your look up table will fit in memory.
• You need to access all information in a BY group at the same time.
• The number of items in your look up table changes for every execution.
• You could use an array, but don't know how large to make it.
• You could use a custom format, but have multiple variables associated with each key.
• The key contains multiple variables, some character, some numeric.

The full code is in the "Downloads" tab.

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These sample files and code examples are provided by SAS Institute Inc. "as is" without warranty of any kind, either express or implied, including but not limited to the implied warranties of merchantability and fitness for a particular purpose. Recipients acknowledge and agree that SAS Institute shall not be liable for any damages whatsoever arising out of their use of this material. In addition, SAS Institute will provide no support for the materials contained herein.

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These sample files and code examples are provided by SAS Institute Inc. "as is" without warranty of any kind, either express or implied, including but not limited to the implied warranties of merchantability and fitness for a particular purpose. Recipients acknowledge and agree that SAS Institute shall not be liable for any damages whatsoever arising out of their use of this material. In addition, SAS Institute will provide no support for the materials contained herein.

1    /* hashsize.sas */
2    
3    options fullstimer msglevel=i nosource;
152  
153  /* remove the asterisk in front of the macro call you want to run
153! */
154  
155  /* 3K rows, 1 key variable, $4, 2 data variables, 1 numeric, 1 $10
155! */
156  %hash_test (rows=3000,keycnt=1,datacnt=2,
157              K1LEN=4,K1TYP=C,
158              d1len=8,d1typ=n,d2len=10,d2typ=c); run;
ROWS=3000
KEYCNT=1
DATACNT=2
K1LEN=4
K1TYP=C
D1LEN=8
D1TYP=N
D2LEN=10
D2TYP=C

XMLRMEM available =                1,248,723,968
Actual table size:                       144,000 bytes
Row          size:                            48 bytes
Optimal   HASHEXP:                            12
159  /* 30K rows, 3 key variables, numeric, no data variables */
160  %hash_test(rows=30000,keycnt=3,
161             k1len=8,k1typ=n,
162             k2len=8,k2typ=n,
163             k3len=8,k3typ=n,
164             datacnt=0
165             ) ; run;
ROWS=30000
KEYCNT=3
K1LEN=8
K1TYP=N
K2LEN=8
K2TYP=N
K3LEN=8
K3TYP=N
DATACNT=0

XMLRMEM available =                1,248,723,968
Actual table size:                     1,920,000 bytes
Row          size:                            64 bytes
Optimal   HASHEXP:                            15
166  /* 30K rows, 3 key variables, numeric, 1 data variable, $1 */
167  %hash_test(rows=30000,keycnt=3,
168             k1len=8,k1typ=n,
169             k2len=8,k2typ=n,
170             k3len=8,k3typ=n,
171             datacnt=1,d1len=1,d1typ=c
172             ) ; run;
ROWS=30000
KEYCNT=3
K1LEN=8
K1TYP=N
K2LEN=8
K2TYP=N
K3LEN=8
K3TYP=N
DATACNT=1
D1LEN=1
D1TYP=C

XMLRMEM available =                1,248,723,968
Actual table size:                     1,440,000 bytes
Row          size:                            48 bytes
Optimal   HASHEXP:                            15
173  /* 5K rows, 1 key variable, numeric, 1 data variable, $84 */
174  %hash_test(rows=5000,keycnt=1,
175             k1len=8,k1typ=n,
176             datacnt=1,d1len=84,d1typ=c
177             ) ; run;
ROWS=5000
KEYCNT=1
K1LEN=8
K1TYP=N
DATACNT=1
D1LEN=84
D1TYP=C

XMLRMEM available =                1,248,723,968
Actual table size:                       560,000 bytes
Row          size:                           112 bytes
Optimal   HASHEXP:                            13

Predicting how much memory a hash table uses can be difficult. The amount of memory needed includes internal structure requirements as well as space for alignment inside the table.

The code below defines a macro that can be used to build a hash table containing key and data variables of the size and type needed for your program. You can specify the expected number of rows for the hash table.

The macro creates a DATA step that shows the amount of memory available before the DATA step starts, along with the size of the table, the size of each row and an optimal HASHEXP value.

There are example macro calls at the bottom of the macro definition. Change one of the execution to reflect the attributes of your hash table.

Download macro and test executions

Want to find out how much memory your hash table needs before writing the program? Here is a macro that you can use to find out.

Type:

Sample

Date Modified:	2008-12-22 15:02:05
Date Created:	2008-12-12 16:01:23

Operating System and Release Information

Product Family	Product	Host	SAS Release
			Starting	Ending
SAS System	Base SAS	z/OS	9.2 TS1M0
		Microsoft® Windows® for 64-Bit Itanium-based Systems	9.2 TS1M0
		Microsoft Windows Server 2003 Datacenter 64-bit Edition	9.2 TS1M0
		Microsoft Windows Server 2003 Enterprise 64-bit Edition	9.2 TS1M0
		Microsoft Windows XP 64-bit Edition	9.2 TS1M0
		Microsoft® Windows® for x64	9.2 TS1M0
		Microsoft Windows Server 2003 Datacenter Edition	9.2 TS1M0
		Microsoft Windows Server 2003 Enterprise Edition	9.2 TS1M0
		Microsoft Windows Server 2003 Standard Edition	9.2 TS1M0
		Microsoft Windows XP Professional	9.2 TS1M0
		Windows Vista	9.2 TS1M0
		64-bit Enabled AIX	9.2 TS1M0
		64-bit Enabled HP-UX	9.2 TS1M0
		64-bit Enabled Solaris	9.2 TS1M0
		HP-UX IPF	9.2 TS1M0
		Linux	9.2 TS1M0
		Linux for x64	9.2 TS1M0
		OpenVMS on HP Integrity	9.2 TS1M0
		Solaris for x64	9.2 TS1M0