A very common issue we all face is comparing cases or scenarios of models we
run. It would be usefull to classify models based upon a set of
assumptions they may use. Yet storing each 100's of assumption values in
each case could be very daunting and consume huge amounts of space.

One solution is to create a range of input parameters that infrequently
change, then calculate a single hash value that represents the range.
When you run the model, you store the results, the frequently changing input
assumptions, and the hash value of the all the other assumptions.

You check the hash value against the database. If you find a match you know
you already stored all the infrequently changing assumption. If no match,
you stort the hash and all its corresponding inputs only once. Now with
the hash, it is easy to compare and contrast all the models with similar
sets of assumptions.

Question: Is there an easy way convert a range of cells into a Long
Integer hash value?

Stephen Bullen posted a very helpful hash algorithm that returns a hash that
is a 30 character string. (Thank you, Stephen!!!)
From: Stephen Bullen )
'Subject: Hash (MD5) in Excel
'Newsgroups: microsoft.public.Excel.programming Date: 2004-02-05
12:50:20 PST

I made a small change:
For Each oCell In rngData.Cells
If Not IsEmpty(oCell.Value) Then
vValue = oCell.Value
Else
'rasey 040608
vValue = oCell.Column * 256 + oCell.Row 'rasey
040608
End If
lResult = CryptHashData(hHash, VarPtr(vValue),
LenB(vValue), 0&)

Stephen skipped Empty cells, but I record a unique value for each empty cell
so that the position of assumption values is important to the hash instead
of simply the order of values.

While Stephen's original function returns a 30 character string, only the
first 16 are non-blank.

I am not after high security, just a simple quick index of assumptions of a
model run millions of times on a couple hundred assumptions. 16byte keys
are overkill for me.

Before I build by database using 16 byte string Primary Keys, I want to ask:
Is there an argument of CryptCreateHash or CryptGetHashParam that will
return a Long Integer instead of a string?

Thanks to all in advance.
And special thanks to Stephen Bullen for getting me 99.9% of the way.

Stephen Rasey
WiserWays
Houston, TX

For convenience, I am reposting Stephen Bullen's code from the 2004-02-05
post below:
Option Explicit



Declare Function CryptAcquireContext Lib "advapi32" Alias
"CryptAcquireContextA" (ByRef hProv As Long, ByVal sContainer As String, _

ByVal sProvider As String, ByVal lProvType As Long, ByVal lFlags As
Long) As Long



Declare Function CryptCreateHash Lib "advapi32" (ByVal hProv As Long, ByVal
lALG_ID As Long, _

ByVal hKey As Long, ByVal
lFlags As Long, ByRef hHash As Long) As Long



Declare Function CryptHashData Lib "advapi32" (ByVal hHash As Long, ByVal
lDataPtr As Long, ByVal lLen As Long, ByVal lFlags As Long) As

Long



Declare Function CryptGetHashParam Lib "advapi32" (ByVal hHash As Long,
ByVal lParam As Long, ByVal sBuffer As String, _

ByRef lLen As Long, ByVal
lFlags As Long) As Long



Declare Function CryptDestroyHash Lib "advapi32" (ByVal hHash As Long) As
Long



Declare Function CryptReleaseContext Lib "advapi32" (ByVal hProv As Long,
ByVal lFlags As Long) As Long



Const MS_DEF_PROV = "Microsoft Base Cryptographic Provider v1.0"

Const PROV_RSA_FULL As Long = 1

Const CRYPT_NEWKEYSET As Long = 8

Const CALG_MD5 As Long = 32771

Const HP_HASHVAL As Long = 2



Public Function GetMD5Hash(rngData As Range) As String



Dim hProv As Long

Dim hHash As Long

Dim lLen As Long

Dim oCell As Range

Dim baData() As Byte

Dim sBuffer As String

Dim vValue As Variant

Dim lResult As Long



'Get/create a cryptography context

CryptAcquireContext hProv, vbNullString, MS_DEF_PROV, PROV_RSA_FULL, 0

If hProv = 0 Then

CryptAcquireContext hProv, vbNullString, MS_DEF_PROV, PROV_RSA_FULL,
CRYPT_NEWKEYSET

End If



'If we got one...

If hProv < 0 Then



'Create an MD5 Hash

CryptCreateHash hProv, CALG_MD5, 0, 0, hHash



'If that was OK...

If hHash < 0 Then



'Fill it with the contents of the range

For Each oCell In rngData.Cells

If Not IsEmpty(oCell.Value) Then

vValue = oCell.Value

lResult = CryptHashData(hHash, VarPtr(vValue),
LenB(vValue), 0&)

End If

Next



'Create a buffer to store the hash value

sBuffer = Space(30)

lLen = 30



'Get the hash value

CryptGetHashParam hHash, HP_HASHVAL, sBuffer, lLen, 0



'Return the hash value

GetMD5Hash = Left$(sBuffer, lLen)



'Tidy up

CryptDestroyHash hHash

End If



'Tidy up

CryptReleaseContext hProv, 0

End If



End Function

I noticed that the hash value does not change if I change a cell value from
1 to 2 or 200 to 250. It does change if I change it form 1 to 10. or 200 to
2000.

The MD5 Hash seems to be sensitive to the number of characters, not the
actual value.

I am going to research some of the other hashing methods. Does anyone
have some suggestions to try?

Thanks in advance.

Stephen Rasey

Houston

..


"Stephen Rasey" wrote in message
...
....<Clip
Stephen Bullen posted a very helpful hash algorithm that returns a hash
that
is a 30 character string. (Thank you, Stephen!!!)
From: Stephen Bullen )
'Subject: Hash (MD5) in Excel
'Newsgroups: microsoft.public.Excel.programming Date: 2004-02-05
12:50:20 PST

I made a small change:
For Each oCell In rngData.Cells
If Not IsEmpty(oCell.Value) Then
vValue = oCell.Value
Else
'rasey 040608
vValue = oCell.Column * 256 + oCell.Row 'rasey
040608
End If
lResult = CryptHashData(hHash, VarPtr(vValue),
LenB(vValue), 0&)

Stephen skipped Empty cells, but I record a unique value for each empty
cell
so that the position of assumption values is important to the hash instead
of simply the order of values.

While Stephen's original function returns a 30 character string, only the
first 16 are non-blank.

I am not after high security, just a simple quick index of assumptions of
a
model run millions of times on a couple hundred assumptions. 16byte
keys
are overkill for me.

Before I build by database using 16 byte string Primary Keys, I want to
ask:
Is there an argument of CryptCreateHash or CryptGetHashParam that will
return a Long Integer instead of a string?

Thanks to all in advance.
And special thanks to Stephen Bullen for getting me 99.9% of the way.

Stephen Rasey
WiserWays
Houston, TX

For convenience, I am reposting Stephen Bullen's code from the 2004-02-05
post below:
Option Explicit



Declare Function CryptAcquireContext Lib "advapi32" Alias
"CryptAcquireContextA" (ByRef hProv As Long, ByVal sContainer As String, _

ByVal sProvider As String, ByVal lProvType As Long, ByVal lFlags
As
Long) As Long



Declare Function CryptCreateHash Lib "advapi32" (ByVal hProv As Long,
ByVal
lALG_ID As Long, _

ByVal hKey As Long, ByVal
lFlags As Long, ByRef hHash As Long) As Long



Declare Function CryptHashData Lib "advapi32" (ByVal hHash As Long, ByVal
lDataPtr As Long, ByVal lLen As Long, ByVal lFlags As Long) As

Long



Declare Function CryptGetHashParam Lib "advapi32" (ByVal hHash As Long,
ByVal lParam As Long, ByVal sBuffer As String, _

ByRef lLen As Long,
ByVal
lFlags As Long) As Long



Declare Function CryptDestroyHash Lib "advapi32" (ByVal hHash As Long) As
Long



Declare Function CryptReleaseContext Lib "advapi32" (ByVal hProv As Long,
ByVal lFlags As Long) As Long



Const MS_DEF_PROV = "Microsoft Base Cryptographic Provider v1.0"

Const PROV_RSA_FULL As Long = 1

Const CRYPT_NEWKEYSET As Long = 8

Const CALG_MD5 As Long = 32771

Const HP_HASHVAL As Long = 2



Public Function GetMD5Hash(rngData As Range) As String



Dim hProv As Long

Dim hHash As Long

Dim lLen As Long

Dim oCell As Range

Dim baData() As Byte

Dim sBuffer As String

Dim vValue As Variant

Dim lResult As Long



'Get/create a cryptography context

CryptAcquireContext hProv, vbNullString, MS_DEF_PROV, PROV_RSA_FULL, 0

If hProv = 0 Then

CryptAcquireContext hProv, vbNullString, MS_DEF_PROV,
PROV_RSA_FULL,
CRYPT_NEWKEYSET

End If



'If we got one...

If hProv < 0 Then



'Create an MD5 Hash

CryptCreateHash hProv, CALG_MD5, 0, 0, hHash



'If that was OK...

If hHash < 0 Then



'Fill it with the contents of the range

For Each oCell In rngData.Cells

If Not IsEmpty(oCell.Value) Then

vValue = oCell.Value

lResult = CryptHashData(hHash, VarPtr(vValue),
LenB(vValue), 0&)

End If

Next



'Create a buffer to store the hash value

sBuffer = Space(30)

lLen = 30



'Get the hash value

CryptGetHashParam hHash, HP_HASHVAL, sBuffer, lLen, 0



'Return the hash value

GetMD5Hash = Left$(sBuffer, lLen)



'Tidy up

CryptDestroyHash hHash

End If



'Tidy up

CryptReleaseContext hProv, 0

End If



End Function

Re the GetMD5Hash function in the root message.
I have an improved function wwGetMD5Hash below:

The problem with GetMD5Hash is I get the same hash if the cell value is
"aaa" or "ccc", but it will be different if it is "aaaa". (see below for
a table of sample hashes).
The problem centers around VarPtr(vValue). I get better results with
StrPtr(sValue).

When I replace the following from GetMD5Hash:
vValue = oCell.Value
lResult = CryptHashData(hHash, VarPtr(vValue), LenB(vValue), 0&)

With:
Dim sValue as String
...
If Not IsEmpty(oCell.Value) Then
sValue = CStr(oCell.Value)
'rasey o40611
lResult = CryptHashData(hHash, StrPtr(sValue),
LenB(sValue), 0&) 'rasey 040611

I get a hash that that changes on the content of the cells.

I think VarPtr(vValue) must be returning a pointer to memory that "wraps"
the contents of the variant, not the contents of the variant itself.

When I use StrPtr(sValue), I must be getting a pointer to the contents of
the string.
The wwGetMD5Hash used below, not only changes the hash on changes in the
contents of a cell, but it also does not ignore empty cells.

Thanks to Stephen Bullen for the GetMD5Hash. I'd never gotten it myself.

Stephen M. Rasey
Houston, TX

\' wwGetMD5Hash(range) - return a 16 character hash string unique to the
contents of a many cell range.
' Afer GetMD5Hash (written by Stephen Bullen
' Newsgroups: microsoft.public.Excel.programming Date:
2004-02-05 12:50:20 PST )
' modified by Stephen Rasey (WiserWays) 040611
' Changes: Use StrPtr and coerse all cell values to strings
' Empty cells are not ignored, but the cell number in the
range
' is used to generate more data for the hash

Option Explicit

Declare Function CryptAcquireContext Lib "advapi32" Alias
"CryptAcquireContextA" (ByRef hProv As Long, ByVal sContainer As String, _
ByVal sProvider As String, ByVal lProvType As Long, ByVal lFlags As
Long) As Long

Declare Function CryptCreateHash Lib "advapi32" (ByVal hProv As Long, ByVal
lALG_ID As Long, _
ByVal hKey As Long, ByVal lFlags As
Long, ByRef hHash As Long) As Long

Declare Function CryptHashData Lib "advapi32" (ByVal hHash As Long, ByVal
lDataPtr As Long, _
ByVal lLen As Long, ByVal
lFlags As Long) As Long

Declare Function CryptGetHashParam Lib "advapi32" (ByVal hHash As Long,
ByVal lParam As Long, _
ByVal sBuffer As String,
_
ByRef lLen As Long, ByVal
lFlags As Long) As Long

Declare Function CryptDestroyHash Lib "advapi32" (ByVal hHash As Long) As
Long

Declare Function CryptReleaseContext Lib "advapi32" (ByVal hProv As Long,
ByVal lFlags As Long) As Long

Const MS_DEF_PROV = "Microsoft Base Cryptographic Provider v1.0"
Const PROV_RSA_FULL As Long = 1
Const CRYPT_NEWKEYSET As Long = 8
Const CALG_MD5 As Long = 32771
Const HP_HASHVAL As Long = 2


Public Function wwGetMD5Hash(rngData As Range) As String

Dim hProv As Long
Dim hHash As Long
Dim lLen As Long
Dim oCell As Range
Dim baData() As Byte
Dim sBuffer As String
Dim vValue As String
Dim vU2 As Variant
Dim lResult As Long
Dim lcellCounter As Long

'Get/create a cryptography context
CryptAcquireContext hProv, vbNullString, MS_DEF_PROV, PROV_RSA_FULL, 0
If hProv = 0 Then
CryptAcquireContext hProv, vbNullString, MS_DEF_PROV, PROV_RSA_FULL,
CRYPT_NEWKEYSET
End If

'If we got one...
If hProv < 0 Then

'Create an MD5 Hash
CryptCreateHash hProv, CALG_MD5, 0, 0, hHash

'If that was OK...
If hHash < 0 Then

'Fill it with the contents of the range
lcellCounter = 0
For Each oCell In rngData.Cells
lcellCounter = lcellCounter + 1
If Not IsEmpty(oCell.Value) Then
vValue = CStr(oCell.Value)
'rasey o40611
Else
' must use a value for the empty cell not at all
likely to be used be accident.
vValue = "^ " & CStr(lcellCounter) 'rasey 040611
End If
'rasey 040611
lResult = CryptHashData(hHash, StrPtr(vValue), LenB(vValue),
0&) 'rasey 040611
Next

'Create a buffer to store the hash value
sBuffer = Space(30) 'rasey 040608 (Bullen used
30)
lLen = 30 'rasey 040608

'Get the hash value
CryptGetHashParam hHash, HP_HASHVAL, sBuffer, lLen, 0

'Return the hash value
wwGetMD5Hash = Left$(sBuffer, lLen)

'Tidy up
CryptDestroyHash hHash
End If

'Tidy up
CryptReleaseContext hProv, 0
End If

End Function

Example Data (1x3 range, Hash)
| | |=wwgetmd5hash(A1:C1)
aaa | | |íÓ}"o¼µ&ßÚ×óH''
aab | | |gä8Ä
svFõUª^P
aaa | | |íÓ}"o¼µ&ßÚ×óH''
aaaa | | |¤ù/Òë�¾¤Ï©ÅM7Àvå
aaaaa | | |ä?ÅeÓ?"�®K.?"("ê
aaa | | |íÓ}"o¼µ&ßÚ×óH''
aaa |10 | |~!øÖ/©·ù¤&ñ,çò
aaa |20 | |ôû³ÛEz¨mk\?UX°
aaa | | |20f±Lf(¶Çop'üj¤¤
aab | | |gä8Ä
svFõUª^P
baa | | |àK?/*)<O&´"ÚÑ
aaa | | |íÓ}"o¼µ&ßÚ×óH''
AAA | | |ù¹õéeùl^öï¯ÓcÁz'
|AAA | |Ónõ<SsÌ.Wë£'ªs
| |AAA |É-¿'È~vU©ÌáÌ

"Stephen Rasey" wrote in message
...
I noticed that the hash value does not change if I change a cell value
from
1 to 2 or 200 to 250. It does change if I change it form 1 to 10. or 200
to
2000.

The MD5 Hash seems to be sensitive to the number of characters, not the
actual value.

I am going to research some of the other hashing methods. Does anyone
have some suggestions to try?

Thanks in advance.

Stephen Rasey

Houston