Dear all,
I am very puzzled by a program that contains
an else branch that is never executed,
but still seems to slow down the program.
(When I replace it by undefined, the resulting program runs much faster.)
http://hackage.haskell.org/trac/ghc/ticket/5256
I thought it may be a type issue
On Tuesday 14 June 2011, 14:35:19, Johannes Waldmann wrote:
Dear all,
I am very puzzled by a program that contains
an else branch that is never executed,
but still seems to slow down the program.
(When I replace it by undefined, the resulting program runs much
faster.)
Thanks for the analysis.
So is this a problem that should be fixed in GHC?
And what can I do to circumvent the problem?
(Perhaps write some RULES magic?)
Thanks - J.W.
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How is the compiler to know the else branch is never executed at run-time?
If you do, then why is it there in your source code?
On Tue, Jun 14, 2011 at 7:35 AM, Johannes Waldmann
waldm...@imn.htwk-leipzig.de wrote:
Thanks for the analysis.
So is this a problem that should be fixed in GHC?
On 06/14/2011 04:42 PM, KC wrote:
How is the compiler to know the else branch is never executed at run-time?
If you do, then why is it there in your source code?
The algorithm is divide-and-conquer, and I want to create sparks
as long as I have cores (capabilities), and use the linear
algorithm
On Tuesday 14 June 2011, 15:51:57, Daniel Fischer wrote:
On Tuesday 14 June 2011, 14:35:19, Johannes Waldmann wrote:
With id, main1 jumps to foldb_cap, which contains a lot of code for the
(cap 1)-branch, and - that's what causes the slowdown - a worker loop
$s$wfoldlM'_loop_s3EE
On 06/14/2011 04:51 PM, Daniel Fischer wrote:
Note that you get good behaviour when you help GHC a bit, in particular a
static argument transformation
Great! And just in time for my lecture ... - Thanks, J.W.
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Superb; on how to avoid boxing.
On Tue, Jun 14, 2011 at 7:51 AM, Daniel Fischer
daniel.is.fisc...@googlemail.com wrote:
On Tuesday 14 June 2011, 15:51:57, Daniel Fischer wrote:
On Tuesday 14 June 2011, 14:35:19, Johannes Waldmann wrote:
With id, main1 jumps to foldb_cap, which contains a lot
